Novikov G.A.
"Field research of ecology
terrestrial vertebrates"
(ed. "Soviet Science" 1949)

Chapter IV
Quantification of terrestrial vertebrates

Quantitative record of mammals

General instructions

Determination of the number of mammals is carried out in three main ways:

1) By counting animals by direct observations on routes, trial sites or congregation areas;
2) In the footsteps;
3) Trapping.

Depending on the ecology of the species, one method or another is used. Below we look at the most common and practical ways to account for the most important groups of mammals, starting with murine rodents and shrews.

Accounting for murine mammals

Establishing even the relative abundance of mouse-like mammals (small rodents and shrews) is associated with significant difficulties, because almost all of them are burrowers, many are nocturnal, and therefore the possibilities of counting by direct observations are very limited, and often completely absent. This forces one to resort to all kinds of, sometimes very laborious, auxiliary methods (trapping, digging and pouring out of holes, etc.).

The ecological features of small animals and the nature of their habitats determine the predominant development of relative accounting. Some zoologists (Yurgenson and others) generally consider that an absolute count of mouse-like rodents (at least in the forest) is impossible. However, they are wrong, a continuous count is possible, but only involves a lot of work and therefore has no prospects for mass application. Absolute accounting in the forest is especially difficult.

Depending on the task and the adopted methodology, quantitative accounting is carried out either on routes, or on sites, or, finally, without taking into account the territory. The same requirements are imposed on the choice of trial routes and sites for recording rodents as for birds - they must represent the most typical sites, both in terms of habitat conditions and population of animals. The latter circumstance is especially important in this case, since many species are distributed extremely unevenly, forming dense colonies in some places, and completely absent in others. Because of this, with the wrong location of the sites, their insufficient number or small area, major miscalculations are possible. Sites should not be less than 0.25 ha, preferably 1 ha or even more. An elongated rectangular shape is preferable to a square one, as it allows you to more fully cover various conditions. In some cases (see below) round platforms are used.

To obtain reliable information about the density of rodents, the area of ​​the recorded territory should refer to total area of a given biotope or area as a whole, as about 1:100 and up to 1:500 (Obolensky, 1931).

As a result of accounting on sites, in addition to data on the numerical ratio of species in a given biotope, we obtain data on the population density of small mammals per unit area. Under homogeneous conditions and uniform distribution of animals over the territory, it is quite sufficient to establish the number of individuals per 1 ha of a typical area. But if the landscape is mosaic, with a rapid and variegated change of soil-orographic and phytocenotic conditions, then it is more correct to use the concept of "united hectare" introduced by Yu. M. Rall (1936). This concept takes into account the percentage in nature of various biotopes and the number of rodents in each of these biotopes. “Let’s imagine,” writes Rall, “that the area under study contains three main stations A, B, C. On the basis of complex accounting sites (i.e., laid down to account for not one, but all types of small rodents. G. N.), the density any species of rodent per 1 ha in these stations is equal to a, b, c, respectively. Out of 100% of this area in nature, stations occupy: A - 40%, B - 10% and C - 50%. If on an abstract combined hectare (i.e., a hectare that includes three stations) we take the density of rodents according to the ratios of the stations themselves, then we get the density on the combined hectare Р, equal in our example (after reduction to a common denominator):

P= 4a + B + 5c / 10

Thus, we establish the abundance per unit area, taking into account the mosaic distribution of conditions and animals in the habitat, as opposed to the total high and low density, which is usually used in ecological studies. From this point of view, the use of the concept of a united hectare gives all calculations an incomparably greater concreteness and reality and should be widely used not only when processing the results of accounting on sites, but also on routes, where a change in habitat conditions should also always be noted.

Usually, a quantitative account of small mammals covers all species at once, despite the ecological differences between them. Rall proposes to call such a technique complex, in contrast to species-specific. However, in some cases, when it is necessary to study species with specific features behaviors that are not amenable to standard accounting methods (for example, lemmings, steppe lemmings, etc.), then they are specially taken into account.

The most common and well-established method for the relative quantitative accounting of small mammals is accounting using ordinary crushers, developed by V. N. Shnitnikov (1929), P. B. Yurgenson (1934) and A. N. Formozov (1937). In its modern form, this technique boils down to the following: in the place designated for accounting, 20 crushers are set up in a straight line, 5 m from one another.

Crushers are placed, as in the case of collecting, under shelters. The standard bait is black rye bread crusts (preferably with butter), cut into cubes 1-2 cm across. Accounting continues for 5 days.

Inspection is carried out once a day - in the morning. Days during which it rained all the time or only at night, as well as especially cold or windy nights, are excluded from the total count, as obviously not productive.

In practice, this is determined by the complete absence of prey on all transects.

If the animal is not caught, but the trap is clearly lowered by it (the bait is gnawed, excrement remains), then this one is also equated to the caught specimen and is taken into account in the overall results. To avoid such cases, traps should be alerted as sensitively as possible, but not so much that they slam shut from the wind, a fallen leaf, etc., extraneous light touches. The bait must always be fresh and must be changed after rain or heavy dew; it is advisable to renew the oil daily.

Since the results of accounting to a large extent depend on the operation of the crushers, the greatest attention should be paid to their placement and alerting.

The accounting results are refined with an increase in the number of trap-days. Yurgenson believes that for a complete characterization of the abundance of murines in any forest biotope, 20 tape samples with a total number of trap-days equal to 1000 should be laid.

The results of accounting by crushers on a tape sample are expressed by two kinds of indicators:

1) the number of animals caught per 100 trap-days (indicator of prey),
2) the number of all and certain types per 0.1 ha (sample area) and per 1 ha.

Accounting with crushers has a number of indisputable advantages, which provided it with such a wide distribution in various kinds of research. The advantages of the technique include the following:

1) The technique is simple, does not require sophisticated equipment, high labor costs and funds.
2) Crushers with standard bait can catch almost all types of mouse-like mammals, including shrews.
3) Accounting gives quite satisfactory indicators for monitoring the dynamics of the number and comparative assessment of the population of various biotopes.
4) The technique is distinguished by significant efficiency, providing for short term sufficiently massive data (with the help of 200 traps, 1 person can get 1000 trap-days in 5 days, which is quite enough to characterize the biotope).
5) A 100 m long tape sample provides data on the relative density of the animal population per unit area and reflects well the average conditions.
6) Accounting is applicable both in the open landscape and in the forest, and not only in summer, but also in winter.
7) Due to the simplicity and simplicity of the equipment, the technique facilitates standardization and, thanks to this, obtaining comparable data.
8) All mined animals can be used for current work.

Along with this, the described method has serious drawbacks:

1) First of all, it is impossible to get some animals with crushers, in particular, lemmings and steppe pieds, which are very important in their areas of distribution. The opinion that shrews do not easily fall into traps (Snigirevskaya, 1939; Popov, 1945) is refuted by a number of authors (Yurgenson, 1939; Formozov, 1945; Bashenina, 1947).
2) The results of catching and, therefore, accounting are affected by the quality of the manufacture of the trap and the personal abilities of the person making the accounting.
3) The same bait has different effectiveness due to weather conditions and the nature of the biotope (availability of food, etc.).
4) Technical imperfection in the design of crushers, sometimes slammed shut not only by animals, but even by insects and slugs.
5) When high densities of the population and a single inspection of the traps, density indicators are underestimated compared to those found in nature, since a maximum of one animal can be caught in each crush per day. Nevertheless, the relative accounting with crush traps is currently the most accessible and effective, especially in the forest zone.

For quantitative accounting of the water rat, one has to resort to steel arc traps (nos. 0-1), combining captures with direct counts of animals, their nests and feeding tables. Based on the instructions for recording the number of rodents, published in 1945 by the State Institute of Microbiology and Epidemiology of the South-East of the USSR (Saratov) and personal experience A. N. Formozov (1947), we can recommend the following options for the method of quantitative accounting of the water rat under various conditions:

1. Method "trap-linear". Arc traps without bait are placed at all holes of water rats along the coastline on several sections of the coast 50-100 m long, separated from one another by equal intervals (to eliminate arbitrary selection of sites). The traps are inspected daily, the caught animals are taken out, the slammed traps are alarming again. Traps stand for several days, until sharp decline catch. The results of catching are listed for 1 km _ of the same type of coastline. An indicator of population is the number of rats caught in a kilometer area.

2. Method "trap-platform". It is used in "diffuse" settlements of the water rat away from the coastline (on sedge tussocks, semi-flooded thickets of willows, cattail, reeds, wet meadows, etc.). Traps are placed on sites of 0.25-0.5 ha at all burrows, on dining tables and at crossings of water rat feeding paths. If there are a lot of holes, their number is reduced by preliminary digging and traps are set only at the opened passages. Catching lasts two days, with a double inspection of traps (in the morning and in the evening). Accounting results are listed for 1 ha.

3. In late autumn, and in the south, in areas with little snow, and in winter, during the transition of water rats to underground life, the trap-platform technique is modified by setting traps in underground passages.

4. During high water, when water rats concentrate on narrow strips of manes, bushes, etc. along the banks of rivers, the animals are counted from a boat moving along the coast. Recalculation is done for 1 km of the way.

5. In the conditions of extensive settlements in reed and sedge thickets in shallow waters, nests can be counted on sites or ribbons of 0.25-0.5 ha, subdividing nests into brood (large) and solitary ones. Knowing the average population of nests, calculate the number of water rats per 1 ha.

6. In places where nests are hardly noticeable and there is no place to set traps (a lot of water, no bumps, etc.), one has to limit oneself to a visual assessment of the abundance of rats (in points from 0 to 5), counting the number of feeding tables on small areas, tapes or per unit length of the coast, and then converting the obtained indicators to 1 km or 1 ha.

In contrast to the method of quantitative counting with crushers, another one is put forward - counting on trial sites using trapping cylinders. Originally developed by Delivron, it was applied on a large scale in the Bashkir Reserve by E. M. Snigirevskaya (1939). The essence of this technique is as follows. In the studied biotopes, three test sites are laid three times a summer, 50 X 50 m in size, i.e., 0.25 ha. Each site is divided into a network of elongated rectangles with side lengths of 5 and 10 l.

For this, mutually perpendicular lines are marked with stakes, running in one direction at a distance of 10, and perpendicular to it - at a distance of 5 m from each other. With specially made scrapers, along the lines outlined inside the square and its bounding lines, paths 12-15 cm wide are dug; in this case, only the upper part of the turf is removed, and the bare earth is trampled down. At each corner of the rectangles, that is, at the intersection of paths, a trapping can is dug into the ground. It is more convenient to use Zimmer's iron cylinders with a depth of 30 cm, a width of 10-12 cm, with a socket of 4-5 cm and a perforated bottom for rainwater runoff. Cylinders are made in such a way that three pieces fit one into the other.

Snigirevskaya replaced the iron cylinders with ordinary earthenware jars, which, of course, are much more cumbersome. Krynki or cylinders are dug into the ground slightly below its surface. 66 traps are installed on each site.

Rodents, who prefer to run on paths rather than on grass that impedes their movement, fall into pitchers and most of them die of starvation. Snigirevskaya gives a very high rating to this technique, especially emphasizing that it is possible to get into jugs species that are not caught at all or go very poorly into crushes (wood mouse, baby mouse; shrews accounted for over 60% of all animals caught). Once installed, the trapping banks act automatically, do not depend on the quality of the bait and give a large prey (in three summers, Snigirevskaya caught over 5,000 animals).

However, the method of counting with the help of trapping jars suffers from such serious shortcomings that they exclude the possibility of its mass application, except for long-term stationary studies that do not require great efficiency. Detailed criticism is contained in the articles by Jurgenson (1939) and V. A. Popov (1945). The main disadvantages of the analyzed method are:

1) The large bulkiness of the traps used, especially if clay jugs are used. To deliver them to the place of registration, one has to take a cart, and therefore trial sites can only be arranged near roads, which Snigirevskaya herself (1947) notes and which is in no way acceptable.
2) Establishing a trial plot is very time-consuming, as it is necessary to dig 66 holes, dig 850 m of paths. According to A. T. Lepin, this requires the labor of 2 workers for 1-2 days (depending on the hardness of the soil).
3) With a high standing of groundwater and rocky soil, burying pitchers is almost impossible.
4) The large size of the area and the square shape, as shown above, are inconvenient.
5) Cleared paths, especially in dense bushes, greatly change the natural conditions.
6) Jugs are by no means universal traps and even some mouse-like rodents (for example, yellow-throated mice) jump out of them.
7) With large initial labor and installation time and extreme bulkiness, the method gives large catches solely due to the large number of trap-days and therefore cannot be considered particularly intensive, as it seems. It can rather be recommended for obtaining mass material for biological analysis than for the purposes of quantitative accounting. Our attempt to use it in biocenotic studies in the Les na Vorskla Nature Reserve convinced us of the impracticality of this technique. However, one cannot agree with the unconditional denial of this method by P. B. Jurgenson. VA Popov is right when he considers it necessary to simplify the site laying technique.

One of these attempts is the method of counting by trapping trenches in combination with tape catching with crushers, proposed and tested for ten years by V. A. Popov (1945). “In the most typical place for the study area, earthen trenches were dug 15 m long and 40-55 cm deep (experience has shown that the depth of the ditch is not of great importance for the agility of animals), with a trench bottom width of 20-25 cm, and surface of 30-35 cm due to the slight slope of one wall of the trench.

When digging a trench, the earth is thrown out on one side, the one that is limited by the vertical wall of the trench. The construction of a trench, depending on the nature and density of the forest stand and the density of the soil, takes from 1.5 to 4 hours. At the ends of the trench, retreating a meter from the edge, they break in flush with the bottom of the trench along an iron cylinder 50 cm high and 20-25 cm wide (the width of the bottom of the trench). It is good to pour 5-8 cm of water into the cylinders, which is covered with leaves or grass. Otherwise, mice, voles and insects caught in the cylinders can be eaten by shrews, reducing the reliability of the count. The trenches are inspected daily in the morning. All animals caught in the trapping cylinders are counted. In this way, it is possible to take into account not only voles and mice, but also shrews, frogs, lizards and insects.

As an indicator of the abundance of micromammalia, we took the number of caught animals for 10 days of trench operation. At each station, we laid two trenches, placing them in the most typical places for the study area, but no closer than 150 m from one another. We consider the work of two trenches within 10 days, i.e. 20 day-tranches, as a period sufficient to get an idea of ​​the species composition and relative stocks of animals. If it was necessary to obtain more detailed data on the fauna of the site, we increased the work of trenches up to 20-30 days, and for ecological studies we carried out trapping during the entire snowless period.

“This method gives quite objective data, is simple and does not require a highly qualified worker (except for choosing a place for laying trenches).

“The negative side of the method is the difficulty in arranging trenches in places with a high occurrence of groundwater - along the banks of reservoirs, swampy lowlands, alder forests, etc. For a broader characterization of the micromammalia fauna, it is necessary to increase the number of trenches or supplement this method with tape counting with Gero traps. The latter was widely used by us.

Analyzing the results of accounting by trenches and traps given in Popov's article, we ultimately come to the same conclusions as with regard to the methodology

Snigirevskaya - this technique cannot be considered as the main one, capable of replacing tape accounting with crushers. It is curious that Popov himself writes that "... both methods of accounting give fairly close indicators", but, we add, the Yurgenson-Formozov method is incomparably more flexible, operational and applicable in a wide variety of conditions, which cannot be said about the methods associated with earthworks.

Difficulties in direct observation of mouse-like rodents, insufficient objectivity of the results of trapping with crushers involuntarily suggest the idea of ​​finding other methods of relative quantitative accounting and, above all, establishing the possibility of using rodent burrows as a guiding feature. In the steppe regions, burrow counting has found wide application, but in a closed landscape, of course, it cannot play a big role.

Because the burrows different types Since mouse-like rodents are quite difficult to distinguish from each other and are very often used simultaneously by several species, then counting holes can only give summary indicators of the relative abundance of mouse-like rodents as a whole, without differentiation into species. At most, it is possible to divide holes into small (mouse-like rodents) and large (gophers, hamsters, jerboas, etc.). It is also impossible to judge the number of animals inhabiting them by the number of holes, because one animal usually uses several holes.

Since the entrances to uninhabited minks gradually, within 2-3 months, sink, crumble and close, then by the presence of entrances one can judge the presence of animals here at least in the last 3 months before the examination, and by a number of other signs (see above) - select from among the still preserved entrances really inhabited. This makes it possible to use burrow counts for relative counting purposes.

Burrows are counted on routes or on sites. Formozov (1937) recommends conducting route censuses of the number of rodents in the spring, immediately after the snow has melted, in the summer during haymaking and harvesting winter crops, in the fall after harvesting, and in the middle of winter during thaws and fresh snow.

Routes, possibly more straightforward, diverge along the radii from the observation point. The length of each route is up to 10 km, and their total length for each accounting period must be at least 50 km.

Distance is measured by plans, telegraph poles, or by a pedometer.

The width of the accounting strip is taken from 2-3 m, depending on the density of holes and the density of the herbage. To simplify the counting technique, Rall (1947) recommends the use of rope or stick restraints with hanging bars. This device is slowly carried by two workers in front of the counter. With long route counts, the back of the cart on which the counter rides can serve as a limiter.

Routes should evenly cover all critical sites, as is always required in line counting. The directions of the routes are marked on the ground and should remain unchanged from year to year in areas of perennial crops, pastures, pastures, virgin steppe, in ravines and on inconvenient lands. On arable land, you should try to lay routes as close as possible to the counting lines in the previous season. “When taking into account the infestation of crops, in order to avoid damage to the latter, it is advisable to move along roads, borders and outskirts facing virgin lands, fallow and other unsown lands. At the same time, it should be borne in mind that rodents in the fields are especially willing to stay in areas with an undisturbed sod layer (virgin soil, borders, roads) and from here they begin to move, populating crops.

Therefore, the infestation of a crop, taken into account from the boundary or road, will always be higher than the average infestation of the entire area of ​​a given crop. This should be specified in the note to the accounting data. Laying tapes along roads and borders makes it possible to establish the appearance of rodents on crops earlier than this can be done when studying the deep parts of sown areas. Not only burrows are subject to accounting, but also cracks in the soil, which often form in the steppe during hot weather and are readily populated by rodents (especially steppe lemming, herd voles, and others). The population of a crack is determined by the presence of ears of corn dragged there, fresh stems, etc. Burrows are divided into inhabited, or residential, and uninhabited. In this case, the following categories and guidelines can be established:

"1. Inhabited burrow (fresh food remains, fresh droppings, freshly dug earth, traces of urine, paw marks on the dust, a rodent itself is noted, looking out of the burrow, etc.).
2. Open burrow (free passage to the burrow).
3. Burrow covered with cobwebs (often found near recently abandoned burrows).
4. Burrow, partly covered with earth or plant rags.
5. Nora, more than half or completely covered with rags and earth.

It is possible to offer an even more effective way of establishing the habitability of holes, which is widely used when counting in areas - digging holes.

During the count, all minks are trampled or tightly clogged with earth. According to Rall (1947), it is convenient to cover the inlets with lumps or plates of dry cattle manure. The burrow should be closed tightly enough so that the nest is not disturbed by snakes, lizards or beetles.

During precise environmental work, the inlets are blocked by twigs of weeds, straw, etc., laid crosswise, which do not interfere with natural ventilation and the movement of insects and reptiles. The next day after digging, the number of opened holes is counted, which are taken as residential, although it must be borne in mind that one animal can open several entrances. In general, it is very important to distinguish between residential and non-residential minks when counting and processing data, since only by the number of the former one can judge the approximate abundance of rodents, but at the same time, the ratio between the number of residential and non-residential burrows and the change in this ratio indicates the direction of population dynamics - its growth or extinction.

Route accounting allows you to quickly explore large areas and does not require highly qualified workers, which is why it is accepted by the land authorities.

Accounting for holes on the sites is carried out in the same way as on the routes.

The sites are beaten off with a size of 100-250 square meters. m, but in such a way that a total of 0.25-1 ha was surveyed for every 200-500 ha of the total area of ​​the counting area (Vinogradov and Obolensky, 1932). With uniform distribution of rodents, sites can have the shape of squares, and with colonial (spotted) - more objective indicators give elongated rectangles 2-3 m wide. When counting holes in fields among forest belts, just such sites should be taken, placing them in all types of field crops in a straight line across the entire field, starting from the edge of the strip deep into the crop, since under these conditions the rodents are distributed very unevenly and usually concentrate near tree plantations. Therefore, the distance between the sites on the periphery of the field should be less than in its center.

The method of laying the sites worked out by N. B. Biruley (1934) proved to be excellent: “The trial plot is beaten off in the form of a circle, for which a wooden stake is taken, about 1-1.5 m high. It is hammered in the center of the site chosen for accounting. A ring of thick wire is put on the stake in such a way that it freely rotates around the stake, but does not slide to its base, but is always at a height of 70-130 cm from the surface of the earth. One end of the cord is tied to this ring (fishing cord, antenna cord, etc.). The entire cord 30-60 m long is marked every 3 m with twine loops. Then two willow rods 1.5-2 m long are taken. At one end, each of the rods is attached to the loop. The opposite end remains free. The first rod is tied to the very end of the cord, the second - retreating 3 m into the circle to the next loop.

“When counting, the worker, holding the free end of the cord and holding it approximately at chest height, moves in a circle. The observer, on the other hand, walks beside the worker, stepping back a little and inside the circle, and counts all the holes that come across between the willow twigs dragging along the ground. Having made a full circle, the worker transfers the extreme rod to the next loop and winds the remaining 3 m of cord. So, sequentially, in concentric circles, all holes within the plots are counted.

“As you can see from the description, the length of the cord is at the same time the length of the trial plot radius. Therefore, the desired size of the trial plot is selected by changing the length of the cord. With a cord length of 28.2 m, the circle area is 0.25 ha, at 40 m - 0.5 ha, at 56.5 m - 1 ha, etc. It is clear that the width of the counting strip can also be adjusted by increasing or decreasing the distance between the loops to which the rods are attached.

“It goes without saying that the device can only be used in conditions of open steppe, devoid of tall shrubs.

“This method completely solves the tasks. The defined radius of each of the concentric circles automatically excludes the possibility of repeated walking in the same place, without leaving at the same time a missed space. The bars dragging along the ground keep the standard width of the registration strip all the time. The observer only has to go and count the holes.

“The circle method, when compared with the rectangular area method, has the following advantages:

1) The circle method gives greater accuracy and is less tiring for the examiner.
2) With this method of counting, there is no need to have a measuring tape or tape measure.
3) If it is necessary to re-count at the same place, the circle requires the construction of one sign, which is easier to put up and then find. With the method of squares, it is necessary to put four signs.
4) Very labor-intensive moments of work, such as marking the sides and corners of the site, placing corner signs, which are necessary with the method of rectangular areas, disappear completely with our method.

Finding and counting holes in the forest is fraught with such difficulties that it cannot be used for the purposes of quantitative accounting, with the exception of certain special cases. For example, D.N. Kashkarov (1945) describes the count of voles (Microtus carruthersi) carried out in the Zaaminsky Reserve by N.V. Minin. These voles dig minks exclusively under juniper crowns. On an area of ​​1 ha, 83 trees were counted, of which 58 were holes, and 25 were absent.

The average percentage of infection ranged from 64.8 to 70%. The catch for several days under the trees made it possible to approximately determine the number of rodents living there and make a calculation per 1 ha.

We practiced counting burrows on small test plots during biocenotic studies in the spruce forests of the Lapland Reserve.

When working in an open landscape, the method of quantitative accounting by continuous excavation of holes and catching rodents on test sites is very common, which brings us closer to the absolute accounting of rodents. At the same time, this work provides the researcher with massive material for biological analysis.

Burrows are excavated on trial sites. Their number should be such that it covers at least 300-500 holes for each biotope. “Before you start digging up a large complex colony,” advises Formozov (1937), “it is necessary to thoroughly understand the location of individual groups of holes and work according to a well-known system, pushing animals from less complex shelters to more complex ones. In the reverse order of work, when a large group of burrows is first opened, the animals escaping from spare burrows often hide under the layers of earth in a large dug area, which necessitates repeated work in the same place. All groups of burrows are subject to excavation in the (accounting) area allocated for work, regardless of whether there are traces of rodents near them or not... center. It can be useful, in order to make it difficult for the animals to run over to neighboring colonies, at the beginning of the excavation, to open all the available passages for some distance before going deeper to the nesting chamber. In place of the exposed areas, it is desirable to leave trenches with steep walls, 10-12 cm high. This is quite enough to delay for some time the run of not only voles or pieds, but even a faster mouse, which makes it much easier to catch animals jumping out of deep parts of the burrow... For each group of burrows opened, the number of passages is counted, and the total count of burrows in the complex of groups is also given, uniting them into one colony, if its boundaries are clearly visible. At high population densities, when there are no boundaries between colonies, and all burrows connected by ground paths and underground passages, merge into one huge town, a total count of the number of moves (burrows) is given. Each site planned for accounting and excavation must be located within one of any rodent stations ... The pits formed at the site of the excavation are filled up and leveled immediately after the work is completed.

Great importance when excavating holes, it has the simultaneity of its implementation. Depending on the hardness of the soil, excavation requires more or less physical labor, but under any conditions it cannot be carried out by a single observer, since it is impossible to dig, catch quickly fleeing animals and keep the necessary records at the same time. “The results of excavation accounting can vary significantly depending on the skill, conscientiousness of workers and the qualifications of a specialist, the ability to look for burrows where animals hide and understand labyrinths. The tearing of each hole must take place under vigilant control, and this complicates the work of the observer in the indispensable presence of several workers ”(Rall, 1936). According to Rall, because of this, accounting by excavation of holes "... is available only in certain circumstances and, first of all, in the hands of an experienced field ecologist who has material resources."

Accounting by continuous digging of holes and catching animals is applicable, except for steppe species, to lemmings. The easiest way is to dig out the holes of the Ob lemming, since in most cases its passages are located in a peat layer, which can be easily dug out with a knife (Sdobnikov, 1938).

During the processing of excavation data, the following points are noted:

1. The total area of ​​the sites surveyed by the excavation.
2. Total number of dug burrows and number of burrows by rodent species.
3. Average number of holes per 1 ha of the most important biotopes; the same for rodents.
4. Average number of holes in a colony or group.
5. Total number of inhabited and uninhabited colonies or groups of holes. The same - as a percentage of the total amount of the studied colonies. (Inhabited are all colonies and groups in which rodents or fresh food remains were found.)
6. Total number of harvested rodents by species.
7. The average number of holes (passages) per one rodent (including cubs).

If for some reason it is impossible to dig holes (for example, on arable land), pouring animals with water is used. For this, it is best to use a large barrel on a cart and iron buckets, and on hiking trails, canvas ones.

V. A. Popov (1944) used for the relative accounting of the common vole - this most massive inhabitant of meadows and fields - its winter snowy surface nests. These almost spherical nests, woven from grass, lying on the surface of the earth, are especially clearly visible during the period of snow melting and before the development of a dense grass cover. Surface nests were counted on routes laid in typical vole habitats. “During the counts, the length of the crossed station in steps and the number of nests found there were recorded. Accounting is best done in pairs. One, having outlined some kind of landmark (a detached tree, a bush, a haystack, etc.), walks in a straight line, counting steps and marking the stations crossed by a recording tape. The second counts the nests and inspects them, reporting the results for entry in a notebook. In order for the width of the counting strip to be constant all the time, the census takers are tied with a cord 20 m long. The length of the counting route should not be less than 3-5 km, i.e. 6-10 ha. As Popov's observations in Tataria showed, the data on counting vole nests are in good agreement with counting them by trapping with crushers. However, counting surface nests is very simple and therefore can be used as an auxiliary method for the relative counting of some species of small rodents.

Recently, successful attempts have been made to use dogs for the purposes of relative accounting. They have shown themselves especially well in the tundra when counting lemmings, which, as you know, are very badly caught by ordinary crushers. With some training, the dog not only learns not to eat animals, but even to catch them alive. It is better to lead the dog on a leash, which, although it affects its performance, allows you to observe the known width of the accounting tape. Not only rodents are taken into account, but also those for which the dog hunted, but failed to get. With some skill, you can see by the behavior of the dog what kind of animal it is hunting - for a lemming, a Middendorf vole, etc.

Route tracking with a dog gives the best results in the open tundra, and is almost impossible in dense bushes (Korzinkina, 1946). Of course, this method is very relative and comparable only when using the same dog or when scoring.

Lemmings can also be counted on routes on foot, on reindeer and from reindeer sleds. “Walking through the tundra on foot, the observer notes in a notebook all the lemmings that have run out in a strip 2 m wide. The same width will be the counting strip when riding a deer. When riding a sled drawn by three deer, the lane width increases to 4 m.

The best results are obtained when working "in clear, calm weather with a slight frost, when lemmings are most active and, moreover, are easily driven out from under cover by both a walking person and especially trotting deer." Along the way, visual surveys are carried out and the boundaries of the main lemming habitats are marked, or the distance is measured with a pedometer. The data obtained are corrected by continuous captures on test plots and recalculated for the total area (Romanov and Dubrovsky, 1937).

As an auxiliary means of determining the relative intensity of the migration of Norwegian lemmings in the Lapland Reserve, counting the number of carcasses of animals that drowned in the lake while trying to swim across it and were thrown onto the sandy shore was used (Nasimovich, Novikov and Semenov-Tyan-Shansky, 1948).

Relative accounting of small rodents by pellets birds of prey and owls, proposed by I. G. Pidoplichka (1930 and others), proved to be excellent in the steppe regions and became widespread there. S. I. Obolensky (1945) considers it even the main method of accounting for harmful rodents. The technique is reduced to the mass collection of bird pellets, the extraction of animal bones from them, their identification and statistical processing of the material obtained. Collection can be entrusted to technical assistants. The collection is fast; according to Obolensky, exhaustive material for an area of ​​​​200-500 square meters. km can be collected literally in two or three days. At the same time, exceptionally abundant material, numbering many hundreds and even thousands of rodents, falls into the hands of the collector. So, for example, according to the bones from the pellets collected during 12 excursions in the area of ​​the Karaganda Agricultural Experimental Station in 1942, the presence of at least 4519 animals was established (Obolensky, 1945). The number and species composition of exterminated rodents is determined by the number of upper and lower jaws. The remaining parts of the skeleton provide additional material. To facilitate and clarify the definition, it is useful to prepare in advance, by sewing on pieces of cardboard, all the main parts of the skeleton of rodents of the local fauna in order to have samples for comparison with the bones from the pellets.

If the pellets are collected in a certain area regularly and the places of their accumulation are completely cleared, then by the number of the pellets themselves one can judge the relative abundance of small mammals in given time. According to the bones from the pellets, the relative abundance of different types of animals is determined. Although small animals become the prey of predators not strictly in proportion to their numbers, but depending on the way the predator hunts, the behavior of the animals and the nature of the habitat, nevertheless, as the observations of both Pidoplichka and Obolensky showed, “... the numerical indicators of the number of different types of animals established according to the number of their bones in pellets, characterize the quantitative ratios of these animals in nature quite close to reality and are especially suitable for determining the composition of the population of mouse-like rodents ”(Obolensky, 1945).

But both observations of the birds of prey themselves and their relative quantitative count can be used as an indirect indicator of the abundance of rodents, since in general it can be said that the number of both is in direct proportion. Particularly noteworthy are the field, meadow and steppe harrier, short-eared owl, steppe eagle, snowy owl, partly Rough-legged Rough-legged Buzzard and Long-legged Buzzard. “The abundance of predators in winter indicates the well-being of the ongoing wintering of rodents, which in the event of a favorable spring creates a threat to increase their numbers. The abundance of predators during the nesting period indicates that the rodent population successfully survived the critical period of winter and spring; the threat of a sharp increase in the number of rodents becomes real. Finally, in autumn, an increase in the number of predators due to the addition of migrants from neighboring areas to the local nesting ones indicates a significant increase in the number of animals over the summer. In a number of cases, systematic monitoring of predators makes it possible not only to establish the presence of an existing outbreak of "mouse misfortune", but to a certain extent to foresee it.

Observations of predators cannot replace direct observations of the life of a population of small rodents, but they serve as a very useful addition, since predators are clearly visible and easier to take into account. The latter is especially striking when there are few rodents, when their population is dispersed and difficult to count” (Formozov, 1934).

The original method of quantitative accounting using banding was proposed by VV Raevsky (1934). “The method of quantitative accounting we propose,” writes the named author, “is similar to that used in physiology when it is required to determine the total amount of blood in a living organism. So, after inhalation of a certain amount of CO (carbon monoxide - carbon monoxide) or after the introduction of a colloidal dye into the blood, the content of foreign impurities in a small measured volume of blood is determined; the total amount of the latter is derived from the dilution thus obtained.

“In exactly the same way, when we want to determine the number of individuals of any species in an isolated observation area (island, colony, sharply limited station), we catch some of them, ring them and release them back, moreover, in the following samples obtained by catching, shooting, picking up the dead animals, etc., the percentage of occurrence of specimens noted by us is determined.

“Blood circulation in the body guarantees physiologists a uniform distribution of all its elements, and hence the likelihood that the percentage of impurities in the sample taken will be the same as in the entire volume of the blood being studied. When determining the percentage of ringing by taking a sample from one point, we must also be sure that the ringed specimens are distributed fairly evenly in the total mass of the studied population... Such a uniform distribution of ringed individuals in the population that we need is not only possible, but under certain conditions it obviously occurs in nature..."

Raevsky applied his methodology to the study of the ecology of house mice in the North Caucasus, where they accumulate in huge numbers in stacks of straw. Mice are caught by hand, ringed (see below for a description of the ringing technique), and released back. After a few days, n3 is produced; capture, the number of ringed and unringed animals among those caught is counted, and the percentage of ringed animals is calculated. Knowing the number of ringed animals released for the first time (n) and having now established the percentage of marked individuals in the population (a), we can calculate the total number of rodents in the studied population (N), according to the formula

N= n x 100 / a

For example, 26 mice were ringed and released back into the stack. A few days later, 108 rodents were caught here, including 13 ringed rodents (12%). Using the formula, we get that the entire population consists of 216 animals:

N= 26 x 100 / 12 = 216

If there were several recaptures, then the population sizes are calculated using the arithmetic mean.

The checks made by Raevsky showed the high accuracy (more than 96%) of his methodology.

“For the practical application of the method of quantitative accounting by banding, you must have the following prerequisites:

"1. Ringing of the species under study should not present too great technical difficulties, otherwise a sufficiently high percentage of ringing will not be ensured.
"2. The researcher must be sure that in the time elapsed from the moment of banding to the sampling, if it is taken from one point, there was an even distribution of individuals within the population.
“3. The animal population to be counted must live in a limited area.
"4. Knowledge of the biology and ecology of the species should enable the observer to make appropriate corrections to the figures obtained (for example, reproduction between banding and sampling, etc.).”

According to Raevsky, the method of accounting by ringing is quite applicable not only to mouse-like rodents, but also to ground squirrels, gerbils, water rats, bats and other mass animals living in dense colonies.

In a reconnaissance study of murine mammals, one should not miss any opportunity to characterize the state of their population and, in particular, use an eye estimate of their numbers. Numerous correspondents can be involved in this work, as organizations of the crop protection service and the service of forecasting the number of game animals do with success.

N. V. Bashenina and N. P. Lavrov (1941) propose the following scheme for determining the number of small rodents (see p. 299).

According to Bashenina (1947), the visual assessment given by the correspondents is in good agreement with the results of quantitative counting on tape samples by crushers and with the calculation of residential burrows along the routes.

With visual accounting, the scale for estimating the number in points proposed by Yu. A. Isakov (1947) can be used:

0 - The species is completely absent in the area.
1 - The number of the species is very small.
2 - The number is below average.
3 - The number is average.
4 - The number is high, noticeably above average.
5 - Mass reproduction of the species.

At the same time, they use all kinds of observations both on the animals themselves and on the traces of their activity - paw prints in the snow and dust, food, the number of winter nests that melt from under the snow in the spring, etc., since together they can give a lot of interesting and important things and it is good to supplement the data of quantitative records.

Thus, we have at our disposal a number of methods for estimating the number of small mammals that have both positive and negative properties, and it is up to the ecologist to choose the method that best suits the tasks and conditions of work.

However, none of the listed methods provides data on the absolute number of animals in the study area. Meanwhile, these data are very necessary for both theoretical and applied problems.

Some rather successful approximation to this goal is the method of continuous excavation of holes and catching rodents.

But it is applicable only in open landscape conditions. In the forest, the absolute accounting of small mammals is theoretically conceivable by means of their continuous catch on previously isolated sites.

A. A. Pershakov (1934) proposes to lay test sites 10 x 10 m or 10 x 20 m in size, which are surrounded by two earthen grooves, about 70-100 cm deep and 25 cm wide. The inner slope of the inner ditch is gentle, at an angle 45 degrees, and the outer one is sheer. The outer protective groove has a square section. In the corners of the ditches, level with the bottom, trapping banks break in. The inner ditch serves to trap animals escaping from the trial site, and the outer ditch prevents animals from entering from outside. In addition to trapping cans, crushers are used and, finally, trees are cut down and even stumps are uprooted. This shows how laborious the laying of each site is. At the same time, it is possible that some of the animals will run away while digging ditches.

E. I. Orlov and coworkers (1937, 1939) isolated the sites with a steel mesh, and then caught the animals with crushers. The site is beaten off in the form of a square or rectangle with an area of ​​​​400 square meters. m and is fenced with a steel mesh with cells of 5 mm. The height of the mesh above the ground is 70 cm, in addition, in order to avoid undermining, it is buried 10 cm into the ground. Along the upper edge of the net, a double-sided cornice made of tin, 25-30 cm wide, is arranged to prevent animals from climbing over the fence. The mesh is fixed on vertical iron posts that are stuck into the ground. The catch of animals living on an isolated trial site is carried out within 3-5 days with crushers and other traps so as not to miss a single animal. The number of traps should be large enough, 80 m, at least one for every 5 sq. m. After the final isolation of the site and the placement of traps, a schematic plan of the site is drawn up, on which holes, bushes, trees, stumps, numbers of traps are marked, and in the future - places for the extraction of animals (Fig. 73). The trapping stops after nothing has been caught in any of the crushers for three days. Consideration should be given to the possibility of some rodents leaving the fenced area along the branches of trees.

The construction of such an isolated platform requires significant material costs (mesh, tin, etc.), and, according to the authors themselves, is a cumbersome and time-consuming task. It takes 30-40 man-hours to lay out the site.

Rice. 73. Schematic plan of an isolated site for recording mouse-like mammals (from Orlov et al.)

Therefore, accounting at isolated sites cannot yet find application in on a large scale, but only in special stationary studies, for example, in the study of forest biocenoses, where obtaining absolute indicators is absolutely necessary.

For rational hunting management, it is necessary to have information about the number of game animals and their distribution over various types of land. Such data make it possible to establish optimal norms for the extraction of animals and birds, to resolve issues of limiting or completely prohibiting the extraction of certain species, as well as to evaluate conservation and reproduction measures taken on the farm.

Accounting of game animals must be kept by all hunting users who lease hunting grounds and exploit the livestock of game animals. In assigned lands, game managers and rangers of farms can carry out counts, in reserve lands and state reserves - regional game managers, rangers of reserves; All these persons perform accounting work in the order of their official duties. Employees of various hunting organizations and members of the society of hunters can take part in the accounting.

Accounting for game animals is a complex and very laborious task, since, unlike other components of biogenocenoses, the animal population is a very dynamic resource and, with intensive hunting management, animals must be counted annually. Methods for accounting for hunting fauna are complex and time-consuming, which is associated with the hidden lifestyle of animals, and the diversity of the animal world leads to a variety of methods.

There are relative and absolute accounting methods. With relative accounting, only the ratio of the number of animals in different areas or in one area in different years is established. In this case, the assessment of accounting results is made comparative: more, the same, less. Absolute accounting methods allow to find out the actual number of animals in the surveyed area.

Relative counts are less laborious and are quite sufficient for commercial farms. But in Ukraine, where hunting farms serving amateur hunters predominate, the results of this type of accounting are unsuitable for sound planning and rational use natural resources. In such farms, the production of animals is regulated exclusively by their number and an overestimated indicator, for example, during accounting work, will cause "overfishing", which will later be associated with significant costs for restoring the population.

Relative accounting in such farms can only be of auxiliary importance.

Accounting for traces on the route

The main accounting method in hunting farms serving amateur hunters is the registration of animals by tracks, carried out in the winter.

The most widely used accounting for traces on routes is the simplest. The technique consists in the fact that the accountant, moving along the route, registers the traces of animals crossing this route. Having accepted the premise that, under equal conditions of the season and weather, the number of animals is directly proportional to the number of tracks, it is possible, by comparing route records, to establish the ratio of the number by farm plots, by years, seasons, types of land, etc.

Route accounting is simple and not laborious, therefore, attempts were made to carry out absolute accounting on its basis, i.e., to switch from the number of tracks to the number of animals and from linear accounting to area accounting. To do this, combine route accounting with a salary, run or tracking.

One of the widespread hunting methods used in accounting work is trailing animals in the footsteps. The method consists in the fact that the hunter or accountant, having found a fresh trace of the animal, moves along it and reaches the place of lying, thereby discovering the animal itself. Accounting by trailing is carried out on trial plots. Having picked up the area and limited it on the plan and in kind, the accountant traces in turn all the animals, traces of which he discovered. Having reached the lair and frightened the animal, the accountant continues to trail it until the animal crosses the border of the trial plot. After trapping all the animals, their numbers are established on the trial plot.

The trailing method is used to account for moose and deer, hare, fox and other species. With a thorough examination of the trial area, a pass during registration can only be due to animals that did not rise from their hay on the day of registration and were not frightened by the accountant. Such cases are possible only on the days of the first powders in warm weather.

Under no accounting work it is impossible to track all the animals living on the farm in one day, therefore, extrapolation is required for the tracking method. Due to the fact that accounting is carried out on trial plots, it is necessary to select them in such a way that the ratio of land types on the samples corresponds to that in the farm. However, even if this condition is met, the final accounting results may have significant deviations precisely due to extrapolation. Therefore, surveys on sample plots are most often carried out in combination with other methods.

For a long time, the salary method has been used to capture and account for large animals (ungulates and predators). The method consists in the fact that by going around some area and counting all the tracks, separately input and output, the accountant or huntsman, by the difference in the number of input and output tracks, establishes the presence and number of animals in the bypassed area (salary). However, along with the apparent simplicity, there are drawbacks in the method, leading to the fact that in a simple, pure form, salary is rarely used for accounting purposes. The very principle of salary makes it possible to evaluate the obtained objective data in different ways. First of all, such a possibility arises with an equal even number of input and output tracks, when it is not known whether the animals entered the circle and then left, or vice versa, i.e. it is practically unclear whether there are animals in the circle or not. But even the clear predominance of entrance tracks often does not allow one to judge the number of animals, since some of them could first leave and then enter.

In addition, a significant error in the salary occurs due to the animals that are in the circle, but did not leave a mark on the salary line. This is especially often noted in the second half of winter, when the movement of animals is limited by deep snow. All this makes it necessary to abandon the net salary and modernize the method in order to eliminate or reduce gaps. It was proposed to go into the circle at the salary and trail the animals, that is, to abandon the principle of the salary and keep records by tracking. It was also proposed to go not into all the salaries, but into some part of them, thereby determining the skip factor, in other words, by combining the salary and tracking.

The most noteworthy is the experience of the state reserve and hunting economy "Belovezhskaya Pushcha" in applying the repeated salary. With this method, salary accounting is carried out 2 - 3 days in a row. According to the data of the first day, the second is corrected, according to the data of the second day - the first. This made it possible to sharply reduce the percentage of passes, since in the conditions of the forest a deer and a wild boar in rare cases stay for 2-3 days in one block without leaving a trace. When counting the elk, this situation is valid only for the first half of winter, since at the end of winter, elk often stand on plots of several hectares for many days and can easily be missed during salary accounting.

The need to extrapolate salary accounting data depends on the category of hunting management. In farms of the first category, salary accounting is carried out, as a rule, throughout the entire territory and extrapolation is usually not required. At low grades of work, when some part of the territory is covered by the salary, it becomes necessary to extrapolate with all the ensuing difficulties, since one has to extrapolate not from routes, but from trial plots. In these cases, it is more appropriate to use one of the combined methods accounting, which always gives more reliable results than direct extrapolation.

One of the types of accounting for traces on trial plots is the continuous run method. The method consists in the fact that they bypass some part of the land (most often a quarter) and all traces of animals are erased. Then, a noise run is carried out on this area, after which, according to the number of fresh tracks, the number of animals on the run area is determined. pass percentage. The main disadvantage of the method is its high complexity, which hinders its wide application. Due to the high labor intensity, a continuous run is most often used when taking into account species that are difficult to take into account by salary or tracking.

With a continuous run, as with other methods of counting on trial plots, the need for extrapolation arises, which is associated with the same difficulties as with other methods. This circumstance leads to the fact that more and more often continuous run, like other surveys on test plots, is used in various combinations with linear route methods of accounting.

visual accounting

This method consists in the fact that the accountant, moving along the route, registers all the animals seen. The area of ​​the route tape is easy to establish if its length is equal to the length of the counter, and the width is twice the maximum distance to the place of take-off of the bird or to the frightened animal. To reduce the percentage of animals skipping during the route course, the accounting data is corrected by re-passing the route with the dog. Comparison of the data of counts made with and without the dog will give the percentage of missed route counts.

At present, with this method of accounting for animals, there is a wide range of

In quantitative environmental research it is necessary to accurately estimate the number of organisms inhabiting a unit of space (area, volume). In most cases, this is equivalent to determining the population size. The estimation methods depend, of course, on the size and lifestyle of the organisms considered, as well as on the size of the space being examined. The number of plants and sessile or slow-moving animals can be counted directly, or the percentage of surface coverage by different species can be determined to compare their abundance. Indirect methods are used to account for rapidly moving organisms over vast areas. In habitats in which observation of organisms is difficult due to the peculiarities of their behavior and lifestyle, methods of removal or capture-release (marking, "dilution" of the population) are used. All quantitative records, depending on the approach to them, are divided into objective and subjective.

Objective Methods

Toward direct objective methods include those that use square counting, direct observations and photographs, and indirect methods - methods based on the removal of individuals and trapping-release.

Accounting by squares. By counting the number of organisms in a certain number of squares corresponding to a known proportion of the surveyed area, one can easily extrapolate the results. This method allows you to determine three parameters related to the spatial distribution of species.

1. Population density (abundance). Population density is the number of individuals of a given species per unit of space. On land, the number of organisms is counted in randomly distributed squares. The advantage of the method is to obtain absolute accurate estimates that allow one to compare different kinds and territories. Its disadvantages include the complexity and conventionality in some cases of the concept of "individual". For example, plants often form many shoots interconnected by underground parts; to find out whether we are talking about one genetic individual or several, in practice it is very difficult. It is even more difficult to decide whether such individuals, sometimes overgrown over a large area, should be considered as a multitude of individuals or only as one.

2. Frequency of occurrence. It is, in essence, a measure of the probability (chances) of finding a particular species in a randomly placed square. For example, if a species is marked in only one of ten squares, then its frequency of occurrence is 10%. To determine it, you only need to take into account the presence or absence - the number of individuals does not matter. However, it is necessary to choose the area of ​​the square correctly, since the result depends on it. In addition, the general problem of working with squares remains - how to deal with specimens that are only partially within the accounting area (for example, in the case of a creeping shoot rooted outside the square). The advantage of this method is its simplicity, which allows you to quickly survey large areas, such as large forest areas. The disadvantages are that the obtained frequency value is affected by the size of the squares, the size of the individuals, as well as the features of their spatial distribution.

3. Coating. This value shows what percentage of the surveyed area is occupied by a given species - by the bases of its individuals or projections onto the ground of all their parts. Coverage can be measured directly in the field or from photographs, assessed with a Levy instrument, or simply estimated by eye. The method is useful in that it allows one to judge the relative role of different species in a community. It is convenient when the number of individual specimens is difficult to calculate and even theoretically determine (for example, in cereals). However, as a rule, such measurements are either too laborious or subjective.

Direct observation. Direct counting can be applied not only to sessile organisms, but also to fast moving large animals such as deer, wild ponies, lions, birds and bats.

Photographing. By direct counting of individuals in photographs taken from an aircraft, it is possible to establish the size of populations of large mammals and seabirds that congregate in open spaces. You can also use "camera traps" that are installed along the animal trails; the shutter of the camera is released automatically when the animal circuit interrupts the light beam going to the control photocell.

Withdrawal method. This method is useful for estimating the abundance of small organisms, such as insects, in a known area or in a given volume of water. In a standardized way (for example, by making a certain number of sweeps of the net fixed size) catch a certain number of animals, count them, but do not release until the end of the study. The procedure is repeated several more times, with each time the number of caught animals decreases. Based on these data, a graph is constructed, extrapolating which the total number of animals is obtained: it corresponds to the moment when they cease to be caught (zero ordinate), i.e., all individuals of this species are theoretically caught and counted.

Capture-release method. This method involves capturing the animal, marking it in a way that is harmless to it, and returning it to its original place in the population. For example, aluminum disks are attached to the gill covers of fish caught in a net; caught birds are ringed. Small mammals are marked with paint or a section of wool is cut in a special way; arthropods are also marked with paint. In all cases, a specific code should be used to recognize individual individuals. After some time, a second capture is carried out, in which the marked individuals turn out to be “diluted” with those that were caught for the first time.

Ministry of Education and Science of Ukraine

Donetsk National University

Department of Zoology

Abstract on the topic:

"Methods of field studies of the ecology of terrestrial vertebrates"

Prepared by:

5th year student

Group 5 - A

Lebedenko Ludmila

Donetsk 2010

QUANTITATIVE ACCOUNTING

We begin the presentation of the field research methodology with a description of the methods for quantitative accounting of terrestrial vertebrates, without dwelling specifically on methods for studying their species composition and biotopic confinement.

Without a quantitative analysis of life processes, modern ecological research is impossible; knowledge of the number of animals (population density, stock of animals in any locality, etc.) and its dynamics is necessary to solve any practical issues ecology. It is also impossible to indicate a single theoretical aspect of ecology, in which one could operate only with qualitative indicators.

The main task of quantitative accounting is to obtain data on the number of individuals in a known territory, or at least about. the relative abundance of species. Since it is practically impossible to keep a quantitative record of the entire natural population of animals (for example, to directly count all wood mice living in the Saratov region), the ecologist has to work only with samples (samples) from it. In this case, a great and far from overcome difficulty arises in determining the required sample size, the number of samples, and then in extrapolating the data obtained to the entire population. Of great importance for the success of the latter is the correct distribution of counting places in the area under study.

So far, unfortunately, it has not been established which part of the territory under study should be covered by quantitative accounting in order for the latter to give completely reliable results. When establishing sample sizes, researchers are guided by the rule: the more, the better. When choosing places for conducting censuses, they strive to: 1) examine all the differences in the landscape and 2) with the uniformity of terrain conditions, place the census areas evenly, for example, in a checkerboard pattern.

Depending on the purpose of accounting (to determine the number of animals living in a certain territory, or to give only a relative idea of ​​the abundance), it is customary to distinguish groups of methods for absolute and relative quantitative accounting of terrestrial vertebrates. In the group of methods of relative accounting, one can also distinguish between relative indirect and relative direct quantitative accounting.

With regard to the troupe of small mammals (hares, rodents, and insectivores), V. V. Kucheruk and E. I. Korenberg (1964) give the following classification of quantitative accounting methods (Table 1).

Table I

Methods and types of accounting for the number of small mammals (V. V. Kucheruk and E. I. Korenberg, 1964).

Relative indirect	Relative direct	Absolute
Estimation of the number of animals by biological indicators Analysis of the pellets of birds of prey Assessment of the number of mammals but traces of their activities; following footprints in the snow; by the number of feed tables; for food reserves; by the amount of remaining excrement; by the amount of bait eaten; according to the number of entrance holes or holes	Accounting with a set of different traps Use of trapping grooves and fences Accounting for animal encounters on routes Eye estimate of the number of animals Analysis of fur harvesting statistics data Area-trap trapping Accounting for the abundance of animals by mapping their settlements	Estimation of the number of animals in isolated populations using the release of labeled samples Accounting by marking animals and identifying their individual areas Full catch of animals, on isolated sites Accounting by pouring animals with water from holes Continuous excavation, holes with the catch of all the animals inhabiting them Use of burrow population factors Visual counting of animals Warehouse or Run Accounting Complete rearrangement of haystacks, omets and stacks, with a catch of the animals inhabiting them.

From the table above, one can already see how diverse the methods of quantitative accounting of even one systematic group are.

Relative indirect accounting methods

This group includes methods of accounting for the number of mammals by indirect signs without direct observation or obtaining animals. So, for example, it is possible estimation of the number of small rodents by the abundance of birds of prey(method of biological indicators). Back in 1934 A. N. Formozov showed that the habitats and concentrations of raptors change depending on the abundance of rodents they feed on. It is easy to count well-marked birds of prey from a fast-moving vehicle (from the window of a train car, from a motor vehicle) and, in places of their concentration, to identify pockets of increased numbers of rodents. This method is very convenient for reconnaissance purposes when accounting for rodents in large areas. When observing in the same place, the method of biological indicators makes it possible to detect changes in abundance only in years that differ sharply in the abundance of rodents (VV Kucheruk, 1963).

By the abundance of birds nesting in rodent burrows (for example, dancing Wheatears), one can judge the spatial distribution and even the density of settlements of large gerbils, some ground squirrels, and marmots.

Rich material for identifying the species spectrum of small mammals, their distribution and relative abundance provides bird of prey analysis. The ease of detection and collection of pellets and resting places of birds of prey (nests, arrivals) allows a short time get a good idea of ​​the dominant species, and sometimes rare or poorly trapping species. When evaluating the data obtained in this way, one should keep in mind the possible influence on the ratio and abundance of species in the "bites" of the selectivity of bird feeding, the availability of small animals for hunting, etc. Analysis of the pellets of birds of prey is also a common method for studying their diet.

The study of various traces of mammalian activity also provides a number of possibilities for the relative accounting of their numbers. In winter, to account for some ungulates, carnivores and hares, it is widely used counting footprints and a snow after powder on the route. All traces crossing the route are taken into account. Mobility is measured by the number of footprints per 10 km route (calculated separately for each biotope). Some idea of ​​the number of individual species can give counting feed tables(for example, for a water vole), counting feed stocks(haystacks stacked by Dahurian and small pika, etc.), counting the amount of excrement ungulates and hares, accounting for the amount of bait eaten and so on.

Counting burrows or their entrances is the most common method of relative counting of the number of rodents living in open landscapes. This method makes it possible to quickly estimate the abundance and biotopic distribution of animals; burrow counting is, moreover, the first and obligatory stage of work in the absolute accounting of the number of rodents in the steppe, semi-desert and partly in the tundra zone. Despite the fact that the number of pores and inlets in them is not directly dependent on changes in the number of animals, the described method of accounting allows one to get a fairly objective idea of ​​their relative abundance.

Hole counting is carried out on test sites or route tapes of various widths. Platforms size -0.25-0.5-1.0 ha(rarely more) may be rectangular or circular. The former are also used for subsequent absolute accounting, while the latter are convenient only for counting holes. The most concise and at the same time exhaustive description of the method is given in the already mentioned work by V. V. Kucheruk and E. I. Korenberg.

The rectangular platform after marking the corners is intersected by a chain of accountants running at an equal distance from each other. Each recorder counts the holes on the tape between himself and a neighbor walking on the same side. View width ranges from 1 to 10 m depending on the density and height of the grass cover and the size of the burrows taken into account. If the accountant works without assistants, then the site is surveyed while moving by "shuttle". In order not to repeatedly count the same holes, after the next move, the counter puts marks on the corresponding sides of the site, each time moving them to the width of the view.

Round platforms proposed in 1934. N. B. Biruley, lay as follows. A stake is driven in the center of the site, a rope 28.2 long is put on it with a free loop m for a site in 0.25 ha , 40 and 56.5 m for platforms in 0.5 and 1 ha . On a stake at height 11 m they make an emphasis that does not allow the rope loop to slide down, and ribbons are sewn on the rope at equal distances, to which meter-long twigs are tied, which serve as limiters. Mark the starting point on the ground. Then the worker, taking the rope by the end and pulling it at chest level, walks, describing a circle. Each counter, moving in a strip limited by two hanging rods, counts holes. If the account is kept by one person, then, having counted the holes in one lane, he winds the rope to the next mark (rod), makes a new accounting circle, etc.

When accounting for small rodents, groups of pores (“colonies”) are noted, dividing them into residential and non-residential, and the number of inlets. In ground squirrels and marmots, nesting and protective burrows are recorded separately; in both categories, inhabited and uninhabited burrows are distinguished.

Route accounting consists in counting entrance holes, individual holes or their groups on tapes of various widths.

Route counting of small rodent burrows can be carried out in pairs or alone. When accounting is carried out together, the accountants are connected by a cord attached to their belts, the length of which, depending on the density and height of the herbage, ranges from 2 to 6 m . One of the census takers (on the right) measures the distance traveled with a two-meter meter, the other writes down the length of the route in each biotope and the results of the census. Both accountants count family groups of pores, subdividing them into residential and non-residential, and the number of inlets. Burrows are taken into account, not only completely stomping into the counting tape, but also partially falling - on one side of the route (right or left at the choice of accountants). They record at what meter of the recording tape each hole is encountered. When moving from one biotope to another, the distance traveled is noted, and counting in the next biotope is started again.

When the route accounting of small rodents, carried out by one person, they use a limiter in the form of a two-meter rail, at the ends of which rods hang freely. The middle part of the rail is fixed with a belt on the accountant's chest, and hanging rods limit the viewing width. The measure of the distance traveled is the steps of the counter, which are converted into meters during the processing of credentials. To convert steps into meters, the meter walks a pre-measured distance of 100 m and gets a conversion factor (100/number of steps). When this coefficient is multiplied by the number of steps taken, the length of the tape in meters is obtained. In all other respects, the technique of keeping records and recording results by one person does not differ from that of accounting by two.

To determine the number of burrows of great gerbils, three variants of route counts are used.

According to the first option, family burrows ("colonies") of great gerbils are counted on route tapes 20 wide. m . The width of the tape is determined by eye. All burrows that fell into the accounting tape as a whole, as well as those that fell into it partially from any one side of the route, are counted. The number of holes per unit area is determined by dividing the number of counted holes by the route area. However, the number of burrows that fall into the accounting tape depends not only on their number, but also on their size. Therefore, in a plot with large burrows, more of the latter will be taken into account than in a plot with burrows, each of which occupies a small area, with the same number of burrows on an equal area.

Following the second option, on the route, the distances traveled along the area occupied by the hole and between the holes are measured separately. The ratio of the length of the shuti passed when crossing the holes to the entire length of the route gives the desired value, called the “percentage of coverage”. Multiplying the "percentage of coverage" by 100 determines the total area of ​​burrows pa 1 ha the area under study. By dividing the obtained value by the average area of ​​one pore, the number of holes per 1 ha is determined. The average area of ​​one hole is calculated from the area of ​​the circle; the diameter is taken as the average diameter from a series of measurements of holes.

In the third variant of accounting, it is assumed that any linear route crosses as many holes as there are in the strip, the width of which is equal to the average diameter of the holes measured in the direction perpendicular to the route. On a straight route, the route line counts all the holes through which the route line has passed, hitting at least their edge, and measure the diameter of the holes in the direction perpendicular to the route. Density of burrows is determined by dividing the number of counted burrows by the area of ​​the counting tape. With this method of accounting, errors that arise due to the variability of the size of holes and the determination of their average area are excluded.

Increasingly, accounting various mammals and birds. from cars and planes. In different landscape conditions and depending on the size and lifestyle of the object being taken into account, accounting from a car and aircraft can provide indirect data on the relative abundance of animals (counting holes, butanes, etc.), relative direct indicators of abundance (number of animals encountered per route unit ) and even information about the absolute abundance of a particular species within the surveyed area.

In order not to return to the characterization of counting from a car and aircraft, when describing the subsequent groups of counting the number of animals, we deviate from the accepted sequence and consider here all options for auto- and aerial-visual counting.

In relation to birds, as already mentioned, autovisual accounting was applied in 1934 by A.N. Formozov. This method was successfully applied by L. N. Lebedeva in studying the abundance of birds in the Saratov Trans-Volga region in 1960-1965. For the indicator of abundance, she took the number of birds encountered per 10 km route (distance measured by speedometer). At average speed movement of a truck at 25-30 km/h it is possible to take into account the pores of rodents, visible due to large ejections of the earth or other signs. S. N. Varshavsky and M. N. Shilov conducted a census of the number of great gerbils in this way, V. P. Denisov and other members of the expedition of Saratov University in 1960 and 1962. - Accounting for the number of small ground squirrels. Accounting from a car can also be applied to marmots, mole rats, mole voles, zokors, etc.

The use of aerial methods for recording animals and birds in the Soviet Union began in the 1920s, but their widespread use became possible only after the Second World War. VG Geptner (1948) outlined a program of zoological research, the fulfillment of which requires the use of aviation. To date, aerial accounting has firmly entered the everyday life of zoologists, hunters and workers of anti-epidemic institutions (IV Zharkov, 1963).

First of all, aerial surveys were used to determine the stocks of marine mammals, which are better visible from the air than from the coast or sea transport. The world's first aerial surveys were carried out in 1928 by S. V. Doroshev and S. Yu. Friendmam, who found out the distribution of harp seal stocks in the White Sea, using aerial photography of large groups of animals gathering in certain areas for childbearing, and established the total number White Sea harp seal population of 3-3.5 million heads. Since then, when planning annual production sea ​​animal always use air reconnaissance data. Currently, seals are counted from the air in the White Sea, Baikal and the Caspian Sea. In the same way, walruses and even dolphins are taken into account. Abroad, whales, sea otters, seals, sea lions, walruses, sea lions and polar bears are visually and photographically taken from the air. The same method has been used since the 1930s to account for large flocks of waterfowl by the US Fish and Wildlife Service. In the Soviet Union, similar work was carried out on the Caspian Sea by N. A. Gladakov and V. S. Zaletaev in 1954, E. S. Ptushenko on the Sea of ​​Azov in 1956.

It is convenient to take into account from an airplane and animals living in vast treeless and hard-to-reach spaces of the tundra zone. Successful air counts of reindeer were carried out by V. A. Andreev from 1937 to 1961 in Taimyr, by A. B. Vasiliev on the Kola Peninsula, etc. in Canada; since 1948, an aerial survey of deer, caribou, musk oxen, wolves, as well as arctic foxes and ptarmigans has been carried out (Skrobov, 1956)

In the forest zone, aerial accounting can be successfully applied in deciduous forests in winter time. In this way, moose were counted in the Saratov region in 1952. With some methodological additions, it is possible to apply accounting from the air in the zone of sparse coniferous and coniferous-deciduous plantations. To date, a large amount of material has been accumulated on the registration of elk and other forest animals (wapiti deer, white-tailed deer) from the air.

Observations of desert animals from an airplane were first undertaken in 1942 by V. G. Geptner, and the first count was carried out in 1944 by I. D. Shnarevich in the Alma-Ata Reserve (in 2 hours and 30 minutes, all gazelles were counted in the amount of 3700 heads ). Later, saigas were counted in the Astrakhan steppes, in Kazakhstan (there were 663,254 saigas and 2,719 goitered gazelles on an area of ​​307 thousand km2). In the USA, bison and pronghorns are counted in this way. In Africa, M. and B. Grzimek in last years took into account all large mammals and birds: elephants, rhinos, all ungulates, ostriches and even flamingos. IN national park Serengeti, they recorded 3669 animals on an area of ​​11.7 km2. In open landscape conditions, from an airplane it is also possible to count some small animals (marmots, ground squirrels, gerbils) in colony burrows that are clearly visible from the air; beaver settlements (with the exception of coastal beavers), muskrat settlements, etc. are also taken into account.

Thus, censuses of terrestrial (and near-aquatic) mammals and birds from an aircraft (aerovisual, with the help of aerial photography, sometimes in combination with terrestrial censuses) are becoming more widespread and should be assessed as very promising. More details about this relatively new method of quantitative accounting can be found in the article by I. V. Zharkov (1963) “Application of aerial methods for accounting for animals and birds”.

Relative direct accounting methods

Of the methods of relative direct counting of small mammals in those biotopes dominated by various species of mice, voles, hamsters, counting on trap lines (the trap-day method) is most widely used. With the help of Gero-type crushers with a standard bait, placed in a line at a certain interval, they study the territorial and biotopic distribution of animals in various landscape zones (from taiga to semi-desert), characterize the relative abundance, seasonal and multi-year course number of species of small mammals.

Despite the long-standing and fairly widespread use of quantitative accounting of small animals on trap lines, much of this technique causes controversy. There was a need to clarify the following questions:

1) how many traps should an accounting line consist of;

2) what should be the distance between the traps in the counting line;

3) for how long should the trapping lines be set;

4) what should be the standard bait.

In accounting practice, a rule has been developed that the number of traps in the accounting lines should be constant and a multiple of 100. The most commonly used lines of 100, 50 and 25 traps. Until recently, the first option was considered the most desirable, since a line of 100 traps covers a significant area and gives indicators already reduced to 100. However, the large length of such a trap line is its main drawback. As a rule, counting lines with a large number of traps go beyond the contours of individual sections and cross several biotopes. A long accounting line has to be subdivided accordingly into several independent sections, and the accounting results must be recorded separately, for each of them. Such a line, in fact, turns into several lines, closed at the ends and containing a non-standard number of traps. When arranging long trapping lines, it is difficult (in conditions of rough and closed terrain) to maintain a direction, etc.

Apparently, it can be recognized that the most convenient accounting line, consisting of 25 traps. Such a line, in which the traps are separated by 5 m, is easily placed in the vast majority of sections. One observer can set up 6 - 8 lines daily, survey a large area and take samples in several biotopes at the same time.

Carrying out special experiments made it possible to establish that a change in the distance between traps in a line in the range from 10 to 1.25 m does not significantly affect the counting results:

(V. V. Kucheruk, 1963)

Increasing the interval between traps to 10 m slightly increases the catchability of lines, but at the same time lengthens the reference line, which loses the advantages of short lines noted above. Therefore, when using the trap-line method, one should adhere to the recommended by most instructions for counting the number of small mouse-like rodents, an interval between traps of 5 m.

There are different opinions on the question of how long the trapping line should be. In a number of relevant works and instructions, it is recommended to keep the traps on the counting line for several days (more often - for three). Thus, an attempt is made to take into account the main population around the registration line and to level the effect of various marching conditions. The role of such maintenance of traps varies depending on the number of rodents. At low and medium abundance (up to 6.8 animals per 100 trap-days), the catch is the largest on the first day, and on the second it decreases by about 22%, etc. At a high abundance (20 or more animals per 100 trap-days) ) the catch remains unchanged for five days. The frequency of inspection of traps has a very large influence on the catch rate. With a five-fold inspection (per day) of traps on the first day, most of the animals are caught, in the following days the number of animals caught is sharply reduced. As a rule, inspection of traps is carried out 2-3 times a day.

Since, in any case, counting with the help of trap lines gives only a relative idea of ​​the abundance, the main requirement for the method should be its standardity - a condition without which it is impossible to compare the counting results. Apparently, it is most expedient to accept the option proposed by V. V. Kucheruk, to work with lines of 25 traps and limit the catch to one day. The influence of weather and other random factors on the census results can be smoothed out by taking a large number of samples from one biotope. Careful placement of traps has a significant impact on the result of accounting; the number of animals caught increases if the traps are placed not exactly every 5 m, but in the most attractive places for rodents (near burrows, stumps, under deadwood, etc.). This method of arranging traps makes it possible to obtain a characteristic of the abundance of animals not for the entire biotope, but only for its optimal places; it is convenient when the main task is to determine the species composition and ecological distribution of small mammals, but it is undesirable when counting the abundance.

As a bait, a crust of black bread, smeared with vegetable oil, is usually used. The search for more attractive bait was unsuccessful.

The most widely used indicator of abundance when working with trap lines is the percentage of animals caught in traps (ie, the number of animals per 1100 trap-days). An addition to it is usually an indicator of the "specific weight" of species of small mammals, i.e., the percentage of total caught animals, which falls on each species separately.

Along with many advantages that ensured the wide distribution of the described method, it is not without its shortcomings. The main one is related to the unequal attitude of different species of small mammals to the bait. Mice, some voles, and shrews do not take the bait well, and these species, according to the records on the trap lines, look few or absent in this biotope.

Therefore, trapping grooves and fences have been proposed to capture and account for all the animals moving on the surface of the earth.

To account for the number, grooves are most often used: 50 m long, 25 cm wide and deep. Five tin cylinders with a diameter equal to the width of the groove, 40-50 cm high are dug into each groove. The cylinders are located at intervals of 12.5 m, the extreme ones - at both ends of the groove. It is necessary to dig in the cylinders so that their edges are in close contact with the vertical walls of the groove, and the upper edge of the cylinder is 0.5-1 cm below the bottom of the groove. The grooves are bypassed every day early in the morning and the animals that have fallen there are removed from the cylinders. The unit of account is the number of animals caught in 10 days of operation of one groove.

Amphibians and insects are taken out of the cylinder daily in the mass of amphibians and insects that get there. In addition, about once a week it is necessary to clean the grooves from debris that has got there, and wipe the cylinders thoroughly with a rag. During rains, water flows into the cylinders, which must be regularly scooped out.

The grooves can be, as the studies of N.V. Tupikova showed, successfully replaced with fences made of thick cardboard, waste, photographic film, plywood, tin or duralumin. Strips of the listed materials 25-30 cm high are inserted into a groove 2-3 cm deep, cut in the soil with a shovel, and fixed in a vertical position with thick wire studs. When installing, it is necessary to ensure that there are no gaps between the lower edge of the fence and the soil surface. To catch the animals, tin cylinders are used, which are dug in in the same order as in the grooves. The upper edge of the cylinder should lie 2-3 cm below the ground, and the edges of the fence should go 0.5-11 cm into the cylinder. On both sides of the fence, strips of 10-15 cm wide are cleared of grass and debris. Inspection and care of cylinders is no different from those in the grooves. The catchability of grooves and fences turned out to be the same. This makes it possible to recommend fences with cylinders for recording the abundance and mass capture of small mammals in wetlands with a high level of groundwater, on stony soils and in sands, where the use of trapping grooves is impossible.

It has been proven that with the help of trapping grooves, the composition of the fauna of small mammals is much more fully revealed than with other methods of their mass trapping. The number of small shrews, mice, some jerboas, forest lemmings, etc. is most easily estimated by trapping with trapping grooves. It has been established that the change in the population density of common voles from spring to autumn has little effect on the intensity of their capture by ditches. On the contrary, fluctuations in the number of animals over the years are captured relatively well by the grooves. The number of animals that fall into the grooves depends not only on the population density, but also on a number of factors that affect the mobility of animals, namely: on seasonal biological rhythms(reproduction, resettlement of broods, transition to wintering, etc.) and weather (precipitation increases the mobility of animals in summer, a drop in temperature sharply reduces it in autumn).

To account for mammals - inhabitants of open landscapes (some types of tundra, alpine meadows, steppes, semi-deserts and deserts), which have well-marked holes, the catch of animals by traps on accounting sites, proposed in 1935 by Yu. M. Rall, is used. The trap-areal method serves as the main method for accounting for gerbils, ground squirrels, some voles and pikas.

The accounting technique is as follows. On the site (1 ha in size when counting ground squirrels and 0.25 ha when counting gerbils, voles and pikas), traps No. 0 and No. 1 or traps with a ladder surround all the entrances to the holes. If there are many holes on the site, then on the eve of the arrangement of fishing gear they are dug in and traps are set, only at the opened entrances. The duration of fishing sites depends on the type of animals counted. Due to the run of animals to the site from the side, the abundance indicators obtained using the site-trap count are usually significantly higher than the actual density of the population of animals. The most rational terms for fishing sites are established empirically. When taking into account the number of small ground squirrels, the duration of fishing should be equal to 6 hours in the morning (from 6 to 12) with a double check of traps. When taking into account the number of comb and midday gerbils, fishing sites should be carried out during the day. It is necessary to introduce seasonal correction factors to the results of fishing. The number of gerbils caught on the site between March 45 and May 1 should be multiplied by 1.1, from June 1 to July 30 by 2, from September 15 to November 15 by 1.3, and from January 1 to March 1 - by 2. The resulting conversion factors are subject to further experimental verification.

As shown by a number of researchers "(N. K. Deparma, Yu. A. Isakov, N. V. Tupikova, V. M. Neronov), when mapping the animal population over large areas, it is possible to successfully use the statistics of fur harvesting to characterize the level and dynamics of the abundance of mammal species It should only be kept in mind that the size of harvests is not always a direct and adequate reflection of changes in abundance and may depend on a number of reasons related to the organization of fishing, etc.

At various times, methods of counting such as counting various traps using a standard set of traps (the Gassovsky method) and eye estimation of the number of small mammals . In some cases, the named methods; as well as accounting for the abundance of animals by mapping their settlements and deserve application; their description can be found in the work of V. V. Kucheruk (1952), V. V. Kucheruk and E. I. Korenberg (1964).

As mentioned above, the choice of methods for quantitative accounting is made in relation to the studied group of animals; recommendations for techniques and methods for quantitative accounting of individual species and groups of mammalian species are given by G. A. Novikov (1953, pp. 195-542).

Absolute accounting methods

Accounting for the number of all animals living in any large area presents very significant difficulties. Therefore, populations isolated from neighboring ones by natural (or artificial) barriers are convenient for absolute accounting of the number of terrestrial vertebrates. In relation to such populations of rodents, V. V. Raevsky and N. I. Kalabukhov in 1934-1935. it was proposed to keep records of the number of animals in isolated populations using labeled samples. Accounting is carried out by catching, marking animals (banding, coloring, etc.) and releasing marked individuals to the place of their capture. The population size is determined by the ratio of the number of labeled and unlabeled animals in subsequent catches. These relationships are usually expressed as

Proportions r / a = n / x, from which the formula is obtained x = an / r , where x is the desired number, A- number of tagged individuals, n - number of recaptured individuals, among which there were r - previously tagged.

When taking into account the number of mouse-like rodents in stacks of straw, the method turned out to be very accurate, but at the same time V.V. Raevsky pointed out that the use of the method of labeled samples is possible if the capture and ringing of animals is not difficult, if the labeled animals are quickly and evenly distributed among the members of the population , and the population lives in a limited area. When calculating the total number of animals, their reproduction and death during the time elapsed between captures should be taken into account. It should be added to the recommendations of V. V. Raevsky that the death of labeled animals may be somewhat higher.

Subsequently, the method of labeled samples was successfully used by V. N. Pavlinin (1948). for accounting, the number of moles, L. G. Dinesman to determine the absolute number of the agile lizard. Currently, this method is used to account for the number of mouse-like rodents: wild rabbits, protein, bats, as well as ungulates, lizards, turtles and frogs.

Methodological issues related to the determination of the total population size using labeled samples are being developed by many authors in different countries. The American scientist Zippin in 1958 developed a method for counting the number of small mammals by two or more subsequent captures. At the same time, during the study period, the population should remain relatively stable, the probability of falling into traps should be the same for all individuals, and the weather conditions and the number of traps should remain unchanged. Zippin revealed a very interesting pattern, establishing that the accuracy of counting increases not only with an increase in the number of captured and ringed animals, but also with an increase in the total population size. In large populations, it is sufficient to catch a smaller proportion of animals than in small ones. This is illustrated by the following example: with a population of 200 ind. it is necessary to catch at least 55% of it in order to obtain reliable results, while from a population of 100 thousand ind. you can catch only 20% of the animals and get more reliable results.

Subject to necessary conditions the method of labeled samples gives satisfactory results in determining the abundance of mammals, reptiles and amphibians in isolated populations.

The application of this method for counting birds is more complicated (T.P. Shevareva, 1963) and can be used to count isolated populations; for counting migratory birds, the method can be used during nesting, molting or wintering.

Rice. 1. Different methods of fencing and fishing of trial sites: a-fence, b-groove, V-trapping cylinder, g-scapular.

(L.P. Nikiforov, 1963)

The natural development of the described method was proposed by a number of authors (E. I. Orlov, S. E. Lysenko and G. K. Lonzinger, 1939; I. 3. Klimchenko et al., 1955; L. P. Nikiforov, 1963, etc. .d.) to account for various animals, the total catch on isolated sites. Isolation of sites is achieved by enclosing them in various ways and materials: a board fence, a wire mesh fence with or without a tin cornice, a fence made of roofing iron in combination with trapping cylinders, a cord with colored flags, etc. (Fig. 1).

Inside the barriers, the inhabitants are caught before the complete cessation of the entry of animals into. traps. This method has been used to count ground squirrels, gerbils and small forest mammals.

Fishing for isolated sites is an extremely time-consuming method of accounting. If we add to this that it is practically impossible to isolate large areas, and it is difficult to extrapolate data on abundance obtained from small areas, it becomes clear why the fishing of isolated areas is not widespread and is mainly used to obtain correction factors for other methods of accounting. .

Rice. 2. The order of amputation of fingers in rodents for the purposes of marking.

Great opportunities for studying the ecology of mammals were opened by the method of labeling and subsequent release of animals to identify their individual areas. It has become widely used in the study of the mobility and contacts of small mammals and has become one of the methods for absolute counting of numbers.

The essence of the method is as follows: live traps are placed in a checkerboard pattern on the registration area (the size of the area, the interval between traps, the type of live trap are selected in accordance with the size and mobility of the animals under study; in relation to mouse-like rodents, ordinary mousetraps are used, and the distance between the rows of traps and traps and in the series most often is 10 m ), Caught animals are marked, for example, by cutting off fingers (Fig. 2), the place of capture (trap number) is marked and released. In the next catch, the places of capture of tagged and re-caught animals are marked, and the captured untagged animals are tagged, released, etc. note the animals running from the side or migrating through the registration area. However, it often becomes necessary to estimate the number of rodents during field observations, and then the question arises of the time required for such an account.

Apparently, the count could be considered complete as soon as unmarked animals no longer fall into traps (N. I. Larina, 1957), but when laying counting sites among vast biotopes, it is not easy to achieve such a situation. Theoretical calculations (calculation of the empirical formula of the development curve of the catch process) show that the length of the period required for the full catch of the inhabitants of the site depends on the level of abundance. In the case when up to 70 animals were caught per 100 traps daily, the count should be completed on the 15th day. With a daily catch (on the same area and with the same number of traps) of 20-30 animals, it seems possible to achieve their full count only after 40 days. However, in practice (Fig. 3), the number of tagged animals in catches increases rapidly in the first days of counting, and then, having reached 60–70% of the total number of animals caught, continues to fluctuate around this level. Such a state, when at least two-thirds of the inhabitants of the site are marked, is reached by the end of the two-week count. Based on these data, one can get a fairly clear idea of ​​the level of the number of rodents in a given area. Further studies should resolve the issue of the necessary duration of counting for different numbers and mobility of rodents.

When working in open areas, where rodent burrows are clearly visible, a continuous excavation of burrows is used with a catch of all the animals inhabiting them. Since the excavation of holes and the capture of animals coincide in time, it will be possible to take into account only the actual inhabitants of the site. This technique is widely used to account for the common vole and other rodents with shallow burrows. The excavation is preceded by counting the burrows, the holes are carefully plugged with tows of grass. During excavation, the number of excavated holes, inlets, species and the number of animals caught are recorded.

Rice. 3. Quantitative accounting of forest mouse-like rodents on stationary sites:

1- daily catch of rodents in the Bazarno-Karabulaksky district of the Saratov region in 1954; 2 - the same in the Tuapse district Krasnodar Territory; 3 - the number of tagged animals in the daily catch in the Baearno-Karabulak region; 4 - the same in the Tuapse region. I - theoretical curve for the development of the process of catching tagged animals (and an empirical formula for it) in the Saratov region; II - the same in the Krasnodar Territory.

To account for rodents that live in deep burrows on dense ground, where continuous excavation is impossible (for example, to account for ground squirrels), it is replaced by pouring animals with water from holes. Pouring out with water always leads to the fact that some of the animals die in holes and do not come to the surface. According to M. M. Akopyan, the number of small ground squirrels not displaced by water from their burrows is on average about 23%. Consequently, the indicators of the number of animals obtained with this method of accounting are always lower than the actual density of the population of animals.

Recently, the use of burrow population coefficients has become widespread, allowing the relative accounting data to be converted to absolute indicators. Knowing how many animals (of one species or another) per burrow, it is easy to calculate from the density of burrows and their population density. The material for calculating the coefficients is obtained from the data of excavation of holes, pouring, visual accounting, etc.

Visual registration of animals on the sites is used only for large animals with daytime activity, living in open areas with a relief suitable for a wide view. This technique is considered the main one for counting marmots; sometimes used to account for ground squirrels.

To estimate the number of hares in winter (as well as when working with ungulates and predatory mammals) apply run accounting. Several beaters shoutingly move along a narrow rectangular area measuring 6-10 ha and take into account all the traces of hares leaving the site, which correspond to the number of hares. If the account is kept not but with fresh powder, then at the edges of the site all hare tracks are pre-wiped.

Very accurate results are obtained by a complete rearrangement of haystacks, omets and stacks with a catch of the animals inhabiting them. The haystack (omet, etc.) is preliminarily measured and its volume is calculated, after which the straw is laid and all the inhabitants are manually caught. The abundance indicator is the number of animals per 1 m 3 of the substrate.

When assessing the level of the number of animals and extrapolating the accounting data to large areas, one should operate with indicators of the weighted average number. When the number of species in individual biotopes is expressed in absolute terms - the number of animals or their holes per 1 ha or per 1 km 2, it is customary to determine the number per “combined” hectare, “combined” kilometer, etc. Such a “combined” hectare is an abstract hectare in which each biotope has a share proportional to the area occupied by the biotope in a given area .

Let us assume that there are three biotopes in the surveyed area: A (forest), B (steppe) and C (arable land). They occupy 40, 10 and 50% of the total area, respectively. In the forest, the number of the species of interest to us is equal to - a (10), in the steppe-b (20) and in plowing-c (5) animals per 1 ha .

If each of the private indicators of the number of animals in biotopes is multiplied by a coefficient expressing the specific area of ​​the biotope, and then these products are summed up, we will obtain the indicators of the weighted average number (P).

In our (example P \u003d 0.4a + 0.1b + 0.5c \u003d (4a + 1b + 5c) / 10 \u003d (40 + 20 + 25) / 10 \u003d 8.5

In the same way, the indicator of the weighted average number is calculated when working with relative accounting methods.

Relatively rare are cases when a species inhabits all biotopes in the study area. Therefore, especially when characterizing the abundance (reserves) of game animals, indicators referred to units of "total area" or "area of ​​typical lands" are used.

The number of birds, as well as the number of mammals, is determined using various methods of relative (direct and indirect) and absolute accounting. Due to the significant diversity of birds and the diversity of their ecological features, there are no universal methods for their accounting. For each ecologically homogeneous group of birds: small passerines, black grouse, raptors, waterfowl, woodpeckers, colonial nesting birds, etc., variants of accounting methods have been developed that give the most accurate results. Accounting units remain: 1 ha , 1 km 2, 1km, 10 km , 100 km , 1 hour, 10 hours, etc. Compared to mammals, bird counts take a much greater place in route methods, which allow recording bird encounters (visually or by singing). Methods for laying routes and their implementation (pedestrian, automobile) vary depending on the nature of the terrain, the object and tasks of accounting, etc. Along with the relative methods of counting birds on temporary routes, absolute methods of counting small birds are used on routes with a constant width of the counting band , allowing to recalculate that unit of area, to count grouse birds on strip samples, to count grouse protons, to count the number of birds on test sites (more often with the use of taxation or mapping of birds and their nests).

The methodology for accounting for the number of amphibians and reptiles is still poorly developed, and its main drawback is the different, non-standard use of existing methods by researchers. At the same time, there was a need to clarify the reserves of amphibians and reptiles in nature - to clarify not only their relative abundance, but also their biomass (especially amphibians, which feed on many birds and mammals and which themselves exterminate a large number of invertebrates).

To account for amphibians, counting the number of eggs in a clutch and the number of clutches, counting tadpoles, catching with a net, counting amphibian encounters on the route, total catch on accounting sites in 0.1 or 0.5 ha , trapping in trenches or using fences with trapping cylinders, etc. The main requirement when counting amphibians (and reptiles) should be the repetition of counts in the same area and on the same route at different hours of the day (nocturnal amphibians and reptiles take into account with a bright flashlight), different weather and seasons. This requirement is based on the fact that amphibians and reptiles, like poikilothermic animals, are more dependent on climatic and meteorological conditions than homothermal ones, and their activity is functionally related to changes in these factors. When studying the abundance of amphibians and reptiles, due to the high lability of their behavior, it is recommended to combine several accounting methods.

Bibliography

1. Kucheruk VV Accounting by the trap-line method.- In the book. Methods of accounting and geographical distribution of terrestrial vertebrates. (Under the editorship of A.N. Formozov). - M., 1952.

2. Larina N. I. Methods of field studies of the ecology of terrestrial vertebrates. – Saratov: Publishing House of Saratov University, 1968.

3. G. A. Novikov "Field studies of the ecology of terrestrial vertebrates", ed. "Soviet Science" 1949

First of all, it is important to establish the abundance of the studied species, the population density, since it is closely connected with the entire ecology of animals and is of versatile theoretical and applied interest.

Without data on the number of species included in the biocenosis, it is impossible to judge their significance, it is impossible to imagine the structure of the biocenosis and its dynamics in space and time, it is impossible to study the dynamics of populations of individual species.

Knowledge of the number of animals is necessary for the correct organization of pest control, in particular, for making forecasts of the mass appearance of rodents; population density has direct influence on the spread of a number of epizootics; quantitative accounting of game animals is the basis of hunting management planning.

The main objective of quantitative accounting is to obtain data on the number of individuals in a known area, or at least on the relative abundance of species. In accordance with this, two types of quantitative accounting are usually distinguished - absolute and relative. However, it is impossible to draw a sharp line between them, since only in relatively rare cases is it possible to get a really complete picture of the abundance of any species in a given area, but usually the so-called absolute counts give only more or less accurate results. This is not surprising, given the enormous difficulties involved in counting terrestrial vertebrates, which are distinguished by great mobility, caution and secrecy. Even a relative quantitative account of mammals, birds, and reptiles is incomparably more complicated than an account of invertebrates, and even more so of plant objects. This implies the main requirement for any method of quantitative accounting of vertebrates - it should be based primarily on the characteristics of the ecology of the animals counted in a given specific situation.

Therefore, quantitative accounting should be preceded by a preliminary acquaintance with the main features of animal ecology and with the biotopes of the study area. The following points are of the greatest importance, as I. V. Zharkov (1939) showed:

1) The nature of distribution by habitat;

2) The tendency to form more or less permanent groupings: herds, flocks, broods, etc.;

3) The presence of more or less clearly defined hunting areas, overlapping one another or isolated;

4) Tendency to form more or less regular seasonal clusters;

5) Daily and seasonal changes in activity;

6) Daily and seasonal migrations and wanderings.

Therefore, the methodology should be very flexible and different for different life forms of animals in different landscape and geographical conditions and in different conditions. different seasons of the year. Attempts to excessively unify the methodology are doomed to failure in advance. However, for any particular group of animals, it is necessary to strive for standardization of accounting methods in order to obtain completely comparable results. Along with the specified requirements, the method of quantitative accounting should provide sufficiently accurate (in relation to the objectives of the study) results and, moreover, be idle.

Thus, in summary, we can say that the method of quantitative accounting should be based on the ecology of the considered species, landscape and geographical conditions, season, specific research tasks or economic activities and give, with minimal effort and cost, the most reliable results. Failure to comply with any of the above conditions will adversely affect the work.

There are two types of quantitative accounting of terrestrial vertebrates: linear and areal. In the first case, the counting of individuals is carried out along a more or less long line, on both sides of it, and the duration of counting is determined either by time (an hour, two, etc.) or by a known distance. As for the width of the registration band, some authors do not precisely fix it, but determine it exclusively by the distance at which it is possible to reliably recognize animals by ear, with the naked eye and with binoculars, so that somewhere in the steppe this band is for some species (for example, meadow chasings or skates) will be equal to a few meters or tens of meters, and for others (large raptors) - hundreds of meters, which is acceptable only when studying and accounting for one species. But more often, the calculation is made at a certain distance from the main line, sometimes more, sometimes less, depending on the nature of the area and species composition. In this last case, we, in fact, get the same areal accounting with the only difference that the accounting area has the form of a strongly elongated quadrangle. Linear accounting, in which the terrain intersects at a more or less significant distance, is often called an ecological section, or, in the terminology of American ecologists, a transect.

When taking into account the areas, a square or other shape and size area is previously allocated on the ground, determined by the species characteristics of animals.

Both transects and plots should be laid out in sufficiently typical and uniform terrain to facilitate the subsequent recalculation of the obtained data for the entire area of ​​the biotope under study. Summarizing the results of counting on heterogeneous sites (including several biotopes simultaneously, which is quite possible in a mosaic landscape) will require some special techniques, which we will discuss below in the section devoted to rodents.

When establishing registration sites, one also has to take into account the fact that even in relatively monotonous biotopes, animals are distributed unevenly. The nature of the dispersion is the more complex, the more complex and heterogeneous the living conditions.

Depending on the ecology of animals, census can be carried out by direct observation (by ear, with the naked eye or with the help of binoculars), by indirect signs (traces, burrows, excrement, pellets, etc.) or, finally, by trapping.

Accounting can cover both permanent groups of animals and their seasonal accumulations, as well as be carried out during seasonal movements.

Data obtained from animal counts, for ease of comparison, are usually recalculated per kilometer (when counting linearly), per hectare or square kilometer (when counting on trial plots). For game animals, it is advisable to take larger areas - 1000 hectares, i.e. 10 square meters. km. The numbers related to this area are called indicators. In the event that accounting data or figures characterizing the number of animals and birds caught are related to the total area of ​​the entire study area or hunting area, then general area indicators are obtained (for brevity, they are denoted by the corresponding letter symbol; see below). When determining the relative number of animals for individual biotopes or habitats (lands) characteristic of them, indicators are obtained for lands (denoted by the same letters, but with an additional sign).

The indicator obtained by dividing the number of animals by a particular area is called the reserve indicator (z and z1). When using the data on the relative accounting of animals by footprints, they are recalculated either per 1000 ha or per 10 km of the way and an accounting indicator is obtained (y and y1). Production indicators are denoted by d and d1 output indicators (i.e. harvesting) - v and v1.

When organizing quantitative accounting and processing the results obtained, one has to operate with quantitative indicators that need not only a biological, but also a mathematical explanation. In connection with the latter, the following considerations of Prof. P. V. Terentyeva (in litt.): “Unfortunately, the mathematical theory of quantitative accounting has not only not yet been developed, but most researchers do not even realize what exactly the figures they have obtained are. From a statistical point of view, any quantitative account (with the exception of rare cases of a continuous, absolute account of all individuals throughout the territory) is a “selective study”: from the “general population” (the entire area, biotope or population), one or more “samples” of that or other size. You can mathematically prove the following statements:

1. The more samples are taken from the total population, the more reliable the result.

2. The larger the area or size of each sample, the more revealing the data obtained.

3. The distribution of sampling sites within a homogeneous biotope should not be biased, otherwise the data obtained will lose their indicativeness (“representativeness”). In many cases, a staggered order can be recommended.

4. The more variable the phenomenon and, accordingly, the indicators obtained, the greater should be the repetition of observations and the number of samples.

5. Mass phenomena and rough dependencies are captured already with a small number of samples and repetitions, and vice versa.

6. The final accuracy of a statistical result depends more on the number of replicates than on the sensitivity of an individual observation. Of course, it is necessary, however, to strictly observe the standard methods.

7. The reliability of transferring the results of sample studies to the general population (“extrapolation”) is the higher, the larger the area or part of the total population was covered by the samples and the greater the repetition.

The exact expression of these dependencies can be derived from the formulas of any course of mathematical statistics.