ANIMAL MIGRATION
regular movement of an animal population, during which individuals from one area of ​​\u200b\u200bhabitat move to another, but then return back. Such circular travel may be seasonal, like the spring or autumn migration of birds, or it may take a lifetime to complete, as is seen in some Pacific salmon. Animal migrations have a pronounced adaptive (adaptive) character and arose in the process of evolution among the most different types. Examples are the seasonal movements of microscopic animals from the deep part of lakes to shallow waters associated with changes in water temperature, or the migration of whales that swim from the polar regions to the subtropics in autumn, where their cubs are born, and return back to cold waters at the end of spring. It is practically impossible to find at least two species of animals migrating in exactly the same way. Some move singly, others only in groups. Some move at the same time very slowly, while others move very quickly and practically without stopping. For example, Arctic tern migrations are annual flights from areas close to North Pole(only a few degrees away from it), to areas where there are already antarctic ice. On the other hand, some frogs move only a few hundred meters during the year, separating the river from the nearest pond where they breed. In addition to migrations, animal populations can also demonstrate other types of movements. Some animals lead a nomadic lifestyle, and their movements are random in nature and are determined by the specific conditions prevailing in certain places. For example, many large herbivores that live in herds on the plains East Africa, move depending on the availability of food and climatic conditions in one area or another. These movements may take place along unsettled routes and are not associated with a mandatory return to the starting point. Another type of population movement is the so-called. "invasions" characteristic of some birds, mammals, as well as many insects. Invasions are usually observed in regions characterized by a harsh climate with sharp seasonal fluctuations. A well-known example is the brown lemming in the arctic tundra. During a 3-4-year cycle, the number of these animals increases, and after reaching a certain maximum, it quickly decreases. Upon reaching the peak of numbers, when the tundra is literally teeming with lemmings, they leave their native places en masse and go on a long journey. So many become victims birds of prey and mammals, while most others die of disease and starvation, or drown in rivers and lakes or in the sea. However, some manage to survive a difficult time, and the population cycle begins again. The polar owl, also living in the Arctic regions, preys not only on lemmings, but also on hares. In those rare winters when there are few lemmings and hares, the snowy owl moves south in search of prey, sometimes even reaching California. Similar sudden invasions are sometimes observed in some seed-eating birds, usually staying in one area. For example, species living in the highlands or in northern latitudes, such as the Asian and North American nutcrackers, as well as the crossbill, in the years of crop failure of coniferous seeds - their main food - demonstrate disorderly movements from northern latitudes to more southern latitudes or from mountainous areas into the valleys. Among insects, several species of locusts, found in Africa and Asia, have gained particular fame, and make mass flights when a very high population density is reached and there is a shortage of food. Moving to new areas, swarms of locusts can literally outshine the sun; only very few remain in the places where they were born. Unlike invasions, many other movements made by populations are hardly noticeable. They occur slowly and sometimes lead to a change in the distribution area of ​​a particular species. Thus, over the past 30,000 years, man has migrated from Asia through the Bering Strait to North America, and then moved south as far as South America.
Food security. The farther from the equator certain land animals live, the more noticeable seasonal fluctuations in their food supply. In the tropics, the amount of food available, although varying with the alternation of dry and rainy periods, remains fairly constant throughout the year as a whole. As you move north or south, seasonal changes begin to appear. For example, in the tropics, insectivorous birds have a more or less constant amount of food at their disposal, while those nesting in Alaska or northern Canada are faced with the fact that there is a lot of food in late spring - early summer and very little in late summer - early autumn; as a result, migration to the south from places that were so favorable during the nesting period becomes absolutely necessary for survival. During the winter months in northern North America and Eurasia, lakes, rivers, and mud flats are ice-bound, serving as the main feeding grounds for many waterfowl and marsh birds in the summer. It is not surprising that the flight to the south is absolutely obligatory both for these birds and for the various raptors hunting them. Ecological analogs of insectivorous birds among mammals are small insectivorous bats, active (unlike birds) at night. In the northern latitudes, where it is cold in winter and there are no insects, many bats hibernate. Some species, such as gray bat(Lasiurus cinereus) and her close relative- red leather (Lasiurus borealis), migrate south to warmer areas, where they remain active throughout the winter.
Reproduction. In many cases, the migration of animals is associated with the characteristics of reproduction. Some fish and marine mammals are examples. Different kinds Pacific salmon fish of the genus Oncorhynchus spawn in rivers west coast North America and east coast Asia. To spawning grounds, they sometimes have to climb up the rivers a thousand kilometers from the mouth. After spawning, adults die, and fry hatched from eggs grow and gradually slide into the sea. This journey can last from several weeks to many months, but only once in the sea, the fish begin to properly fatten and grow very quickly. Having reached sexual maturity, which takes from one to several years (depending on the type of fish), they return to the very rivers where they were born. There they breed and die, repeating the fate of their parents. Among marine mammals particularly impressive breeding migrations are demonstrated by gray whales. During summer months they stay in the Arctic Ocean and the Bering Sea, where at this time there is an abundance of small marine organisms (plankton) - their main food. In autumn, having accumulated a large amount of fat, the whales begin to migrate south to warmer areas. Moving along the Pacific coast of North America, most whales reach shallow lagoons off the western shores of the Gulf of California, where they give birth to cubs. In March, males, as well as females without cubs, begin to migrate northward, and after a few weeks, females with cubs follow them along the same route. At the beginning of summer, they all reach the cold waters of the Arctic and Subarctic. The purpose of the journey to the south undertaken by the whales is the stay of their cubs in warm water during the first few weeks of life, until they have formed a layer of fat that can reliably protect against the cold in the northern seas. The migration of whales to the north is primarily a return to places rich in food.
Climate and day length. In the study of migration, it can be very difficult to separate the influence of climatic factors from those related to the supply of food or dictated by the characteristics of reproduction. The biological productivity that creates a food base for certain animals is itself largely determined by climate, and in areas far from the equator, the amount of food available often depends on temperature. For many organisms, the length of daylight is also very important, which regulates the normal reproduction cycle. The amount of light received per day, the so-called. photoperiod, often directly stimulates the start of migration. In many birds, for example, the activation of the sex glands, as well as migratory activity, directly depend on the spring increase in the length of daylight hours.
see also BIRDS .
Periodicity. In some animals, migrations correlate with the lunar cycle. One of the most famous examples- grunion (Leuresthes tenuis) - a small fish that lives off the coast of California and northwestern Mexico. From early spring to early autumn, she spawns on sandbanks, and spawning occurs only during especially high (syzygy) tides observed in the first three to four nights after the full moon or new moon. During spawning, which lasts 1-3 hours, females are thrown ashore by waves, where they dig a hole with body movements, into which they lay eggs, which are immediately fertilized by males. The next surging wave carries the females back to the sea, and the juveniles hatch from the laid eggs already in the next spring tide.
Changes in the physiological state. Changes in the physiological state of individuals are very often associated with migrations. In addition to the close relationship observed in spring between the increase in sexual activity and the degree of readiness for migration, both in spring and autumn, immediately before migration, rapid increase fat reserves necessary for the energy supply of long flights. Some birds replenish their energy reserves by stopping to feed during their flight, but others cover vast distances with little or no stop. For example, in the golden plover (Charadrius apricarius), the length of non-stop flight over water can reach 3200 km. Tiny red-throated hummingbird (Archilochus colubris), which lives in summer in eastern regions North America, spends the winter in Central America (from Mexico to Panama). In the fall, before migrating, these hummingbirds build up about two grams of fat - this is enough to cover more than 800 km of the path that runs over the waters of the Gulf of Mexico without stopping.
migratory routes. When migrating, each population follows the same route, which requires certain means of orientation. For a long time Animal navigation mechanisms seemed mysterious, but recent research has unraveled some questions. The first step was to determine the routes of movement of animals; used for this various methods tagging (such as ringing birds). If a sufficiently large number of animals were marked and then found in other places, then it is possible not only to trace the route of migration, but also to find out how quickly it occurs and what is the participation of individuals of different sexes and different ages in it.
Orientation to the sun and stars. Vision is one of the main means by which migrating animals plot their route. In this case, some familiar features of the landscape can serve as landmarks, for example mountain ranges, rivers, lake shores or outlines of sea coasts. The ability to recognize the position of the stars at night and the position of the sun during the day may also play a certain role in orientation. The study of celestial orientation in animals began in the late 1940s with the work of the German ornithologist G. Kramer. Experimenting with migratory birds kept in captivity, he came to the conclusion that starlings, being diurnal migrants, are guided during their flights by the sun. A few years later, Franz and Eleanor Sauer were able to explain how birds that migrate at night find their way. Working with small passerines, they found that as long as the stars are not visible, the movements of birds are chaotic. Additional experiments carried out both in Europe and in America confirmed that many birds that are nocturnal migrants orient themselves by the stars during flight. The ability to navigate by the sun and stars is not unique to birds. Experiments with one of the species of toads (Bufo fowleri) living in ponds central regions The United States showed that young, until recently former tadpoles, individuals always move towards the coast. If toads of this age are placed in a circular cage, from which only its walls, the sky and the sun not covered by clouds are visible, then they always move in a direction perpendicular to the line of their native coast. Even if these toads are moved to some other place and placed in the same cages, their movement will again be oriented in the same direction. Similar experiments with frogs, namely the cricket tree frog, have shown that they can navigate both by the sun and by the stars. Orientation to the Sun was also found in white perch, a fish that lives in many freshwater lakes in North America. When the spawning period approaches, these fish from the open part of the lake move to the shore. If they are caught where they spawn and released in the same lake, but in the central part of it, they begin to move in the direction of the places where they were caught (this has been demonstrated using floats attached to their backs with thin nylon threads) .
Orientation with the help of smell. Orientation, based on the perception of smells, is extremely important for many organisms - from insects to mammals. An example of this is the monarch butterfly, which makes large seasonal movements. In autumn, males are the first to set off along a strictly defined route; odorous glands on their wings leave an odor trail, which is used for orientation by females flying behind them. Having reached the wintering grounds, the butterflies accumulate on the trees in huge numbers, and in the spring they set off on their way back to the north. Several species of Pacific salmon, returning from the sea to the very rivers where they were born, orient themselves with the help of the characteristic smell of the waters of their native river, imprinted in them from the first days after hatching from eggs. This odor is determined both by the minerals in the watershed and organic matter present in the waters of the river and giving it a chemical identity.
currents. The currents are playing important role in the life of animals living in the seas, as well as in rivers (especially where visibility is limited). Amazing migrations associated with ocean currents are made by European and American eels (representatives of the genus Anguilla). Those that live in Europe grow and mature in the rivers that flow into Atlantic Ocean- from Scandinavia to the Iberian Peninsula. After spending 5 to 20 years there and reaching sexual maturity, they roll into the sea, then, drifting with the Canary and North Equatorial currents, cross the Atlantic Ocean and reach the Sargasso Sea - a specific area in the northwestern part of the Atlantic, where there are no currents and in abundance large algae floating near the surface develop. In these places, at great depths, eels multiply, after which they die. The hatched larvae rise to the surface and are transported with the waters of the Gulf Stream to the shores of Europe. This journey takes them three years, and by the end of it, the eels are already able to move up the river systems, where they remain until puberty. Similar migrations are made by American eels living in the rivers of the Atlantic coast.
Impending dangers. Migration always requires the consumption of stored energy, and the amount of energy needed to cover long distances must be simply enormous. Therefore, migratory animals are always in danger of physical exhaustion. In addition, they easily fall prey to predators. Successful overcoming of the migration route to a very large extent also depends on climatic factors. The sudden onset of a cold front during the northward migration of birds in spring can have fatal consequences for many birds, and fogs and storms cause them to lose their bearings and go astray. A serious danger for many migrants is a person. Knowing the routes commercial species animals, people hunt them for food or for other purposes, including purely sporting ones. Various structures, such as television towers and skyscrapers, also cause the death of hundreds of thousands of birds. The blocking of rivers by dams creates obstacles for the rise of fish upstream to spawning grounds.
See also BIOLOGICAL RHYTHMS.
LITERATURE
Cloudsley-Thompson D. Animal migrations. M., 1982

Collier Encyclopedia. - Open Society. 2000 .

See what "ANIMAL MIGRATION" is in other dictionaries:

    - (from lat. migrans) regular movement of an animal population, during which individuals from one habitat move to another, but then return back. Migrations are most common in birds (bird flights) and fish (for example, ... ... Wikipedia

    Regular and directed movements of animals “back and forth”, from one spatial unit (habitat) to another, caused by changes in the conditions of existence in their habitats or associated with the cycle of their development. Distinguish random ... ... Ecological dictionary

    animal migration- Movement of animals caused by changes in living conditions in habitats, dispersal with an increase in numbers (lemmings) or associated with their life cycle (ungulates) ... Geography Dictionary

    animal migration- — EN animal migration Movements that particular animals carry out regularly often between breeding places and winter feeding grounds. (Source: ALL)… … Technical Translator's Handbook

    animal migration- gyvūnų migracija statusas T sritis ekologija ir aplinkotyra apibrėžtis Yra reguliarioji (sezono, paros) ir nereguliarioji (per sausras, potvynius ir kt.). atitikmenys:… … Ekologijos terminų aiskinamasis žodynas

Animal migration - regular and directed movements of animals "back and forth" from one habitat to another, caused by a change in the conditions of existence in their habitats or associated with the cycle of their development. Distinguish: periodic ( migratory birds, seasonal migrations of fur seals) or non-periodic (eviction due to lack of food for nutcrackers from the north of Siberia to the south, etc.) migration. They can be passive (larvae, eggs, adults carried by sea currents) and active (locust flights, anadromous fish, migratory birds). Migrations are also distinguished: forage (in search of food), wintering (flounder forms clusters in deep, warmer waters in winter; in the same "wintering pits" they spend cold season bream, pike perch, catfish, etc.).[ ...]

The absence of older animals (5-7 years) in the population indicates a shorter lifespan of amphibians under the influence of wastewater toxicants compared to their lifespan, as previously established, in “conditionally clean” zones (Misyura, 1989). At the same time, this leads to a decrease in the reproductive potential of the population as a whole and the possibility of its existence only if animals migrate to this reservoir from spawning grounds.[ ...]

The regulation of the number of large animals is achieved by strict control of the size of the feeding area per animal. Such control is carried out in various ways (sound signals of neighbors, animal migration, etc.).[ ...]

K. is used to study the migration routes of animals (especially birds), to establish the boundaries of their ranges, the characteristics of seasonal biology, and to solve other problems. COMBINED IMPACT - see Art. Impact on environment. COMMENSALISM, or freeloading [from lat. honeycomb - with and mensa - table, meal] - a type of cohabitation of organisms, when one of them (commensal) constantly or temporarily exists at the expense of the other, without harming it. COMPENSATORY BEHAVIOR - a complex of behavioral reactions of organisms aimed at weakening (compensating) the limiting influence of an environmental factor.[ ...]

Influence of artificial barriers on animal migration. Artificial obstacles that impede the seasonal migration of reindeer are created by the laying of overground, ground and semi-underground main pipelines, power lines, automobile and railways and other extended structures. Animals accumulate in front of such obstacles in huge herds.[ ...]

MIGRANTS [from lat. migratio - resettlement] - migratory animals (see Migration of animals) or substances that easily move in various components of the biosphere (eg, water M., air M.). MIGRATION-WATER HAZARDOUS INDICATOR - see Art. Soil pollution hazard indicators.[ ...]

Land routes of oil and gas pipelines, roads can cross the paths of animal migration. Driven by the will of instinct, animals try to cross them and in doing so expose themselves to additional danger. In practice, there are cases when, as a result of the dismemberment of winter and summer pastures, entire herds of wild deer died.[ ...]

Since July 1982, the Law “On the Protection and Use of Wildlife” has been in force on the territory of Russia. It establishes public responsibility for animal world, declares the position that animals are one of the main components natural environment and an important part natural resources. The law provides for the conservation of the entire species diversity of animals, the protection of their habitat, breeding conditions and animal migration routes, scientifically justified, rational use and reproduction of the animal world, regulation of the number of animals in order to protect the health of humans and farm animals, as well as the prevention of the death of animals during agricultural, logging and other work, the use of plant protection products, mineral fertilizers and other drugs. A special place in the law is given to the protection and restoration of the number of rare and endangered species.[ ...]

Correct routing of roads and design of road structures in the habitats of wild animals is impossible without taking into account the peculiarities of their behavior and habits. Animal migration routes are characterized by various features: the purpose of movement, direction, season, duration. There are regular reversible and irregular migrations, horizontal and vertical (in the mountains), daily and seasonal, active and passive. Depending on the species, large ungulates move alone, in small groups or in large herds, which must be taken into account when designing special crossings for them. herds reindeer or saigas number up to tens of thousands of individuals; moose, roe deer migrate alone or in small herds (up to 7 individuals), wild boars - in groups of 10-15 individuals.[ ...]

The Code of Administrative Offenses of the Russian Federation regulates administrative liability for violations of the legislation on the protection and use of wildlife in Art. 7.11 "Use of objects of the animal world without permission (license)", as well as for offenses in relation to living resources continental shelf(part 2 of article 8.17, article 8.20), in relation to animals in the course of agricultural economic activity(Art. 10.11), in case of violation of veterinary and other rules (Art. 10.6 “Violation of animal quarantine rules or other veterinary and sanitary rules”, Art. 10.7 “Hiding information about a sudden death or simultaneous mass diseases of animals”, Art. 10.8 " Violation of the veterinary and sanitary rules for the transportation or slaughter of animals, the rules for processing, storing or selling livestock products. In Art. 8.33 provides for liability for violation of the rules of the habitat and migration routes of animals, art. 8.34 - for non-compliance with the established procedure for the creation, use or transportation of biological collections, art. 8.36 - for violation of the rules of relocation, acclimatization or hybridization of objects of the animal world, art. 8.37 - for violation of the rules for using them, art. 8.38 - for non-compliance with the rules for the protection of fish stocks, art. 8.35 - for the destruction of rare and endangered animals, art. 8.29 - for the destruction of animal habitats.[ ...]

Bioindication - assessment of the state and changes in the environment by studying the structure, condition, abundance, behavior, in particular migrations, animals and plants.[ ...]

The height of the grid depends on the type of animal most frequently seen on the road. Fences are installed on animal migration routes across roads with a traffic intensity of more than 2,000 vehicles / day (along the border of the right of way) with a height of 2.0 ... 2.5 m at least 0.5 km in each direction from the established traffic path animals. The height of the fence is 2.25 ... 2.80 m for deer, 1.6 ... 1.8 m - for roe deer, 1.2 ... 1.4 m - for wild boars. Fences require careful installation and careful maintenance. Coarse-mesh high fences (nets) keep roe deer, deer, etc., low, fine-mesh fences are suitable for keeping badgers, hedgehogs, etc., smooth-walled steel or concrete structures are used to protect amphibians. In order not to isolate habitats, barriers should be combined with devices that help animals cross the carriageway.[ ...]

Partial damage to the environment caused during oil production can be compensated through the construction of fish factories, fur farms and wild animal feeding points, the organization of specially protected natural areas, financing of regional environmental programs, etc. Compensatory measures should also include the organization of passages on the migration routes of animals through linear communications, tunnels under roads, crossings under structures on piles and pipelines for the passage of large animals.[ ...]

Impact low temperatures, fires, radiation, strong winds will be accompanied by decay ecological systems, reproduction of pests of forests, fields, orchards and orchards. Animals will die from hunger, frost and lack of water. As a result of animal migration, the spread of human diseases to animals will begin. Ultimately, the action of radioactive substances will lead to the death of the animal world. Tropical forests will be especially sensitive, because the plants of the tropics and subtropics do not have a dormant period that allows them to withstand temperatures even above zero.[ ...]

Avoidance of adverse effects - the body's production of such life cycles and behaviors that avoid adverse effects. For example, seasonal animal migrations.[ ...]

Any phenomena associated with noticeable human impacts on nature, the reverse effects of nature on humans and their economy, with life and economically significant processes, mass irregular migrations of animals, are called an environmental problem.[ ...]

The Code of Administrative Offenses establishes that violation of the rules for transportation, storage and use of plant protection products, plant growth stimulants, mineral fertilizers and other drugs that cause harm to wildlife, entails a fine or a warning. Violation of the rules for the protection of habitats, animal migration routes, rules for trade in zoological collections, as well as the rules for sending and exporting objects of the animal world abroad, unauthorized resettlement, acclimatization and crossing of animals also entails a warning or a fine.[ ...]

For biota, the tertiary stage of technogenesis is expressed in the replacement of traditionally typical forms of vegetation with a restorative series or fundamentally new types of vegetation, in a change in the ways of natural migration of animals, in the disappearance of individuals and even entire species of flora and fauna.[ ...]

Environmental advantages of the intermodal corridor: the possibility of combining environmental protection measures on all modes of transport, the localization of impacts along the route (noise, gas pollution, the possibility of active engineering protection of curb green areas, organization of passages for animal migration), modern processing cargo flows.[ ...]

Thus, we see that living organisms adapt to very difficult conditions of existence, which become the norm for them. But such adaptation takes a long time, it takes not hundreds, but thousands of years. It is often necessary to adapt quickly, for example, when animals migrate from their usual habitat due to deteriorating living conditions: natural disasters, geological disasters, floods, droughts, climate change, lack of food. And the body copes with it.[ ...]

Biogeocenoses are open systems; they exchange matter and energy with each other. The substance is transported in the form of gas, liquids, bulk and other materials. The interbiogeocenotic transfer of living matter and energy is noted during the movement of organisms, for example, during the resettlement of plants, animal migrations.[ ...]

Change of conditions in aquatic environment causes certain behavioral reactions of organisms. Changes in illumination, temperature, salinity, gas regime and other factors are associated with vertical (descension into the depths, rise to the surface) and horizontal (spawning, wintering and feeding) migrations of animals. In the seas and oceans, millions of tons of aquatic organisms take part in vertical migrations, and during horizontal migrations, aquatic animals can travel hundreds and thousands of kilometers.[ ...]

For example, in the 60s and 70s the Kalmyk saiga population was restored at the cost of great efforts. Its number exceeded 700 thousand heads. Currently, the saiga in the Kalmyk steppes has become much smaller, and its reproductive potential has been lost. The reasons are various: intensive overgrazing of livestock, excessive use of wire fences, the development of a network of irrigation canals that cut off the natural migration routes of animals, as a result of which thousands of saigas drowned in the canals along their path.[ ...]

Sections of rivers that have been turned into the so-called downstream pools of reservoirs, where they should be covered with a stable ice cover, in many cases lose this property. In the downstream, a winter polynya is formed and functions; a river that does not freeze even in the most severe frosts, and the cover of ice that replaces it downstream turns out to be fragile, uneven and discontinuous. Thus, below each large dam in winter there is an insurmountable barrier to the migration of animals and to the maintenance of economic ties. For example, on the Yenisei River, the winter polynya stretches from Divnogorsk, which is 30 km above Krasnoyarsk, and almost to the mouth of the Angara. By the end of winter, its length is reduced. The usual changes in the length of the winter polynya of the Yenisei River range from 280 to 50 km.[ ...]

The rhythm of phenomena in geographical envelope. The geographic envelope of the Earth is constantly changing, the relationship between its individual components is becoming more complicated. These changes occur in time and space. In nature, there are rhythms of different duration. Short, diurnal and annual rhythms are especially important for living organisms. Their periods of rest and activity are consistent with these rhythms. The daily rhythm (change of day and night) is due to the rotation of the Earth around its axis; annual (change of seasons) - the revolution of the Earth around the Sun. The annual rhythm is manifested in the existence of periods of rest and vegetation in plants, in molting and migration of animals, in some cases - in hibernation, reproduction. The annual rhythm in the geographical envelope depends on the latitude of places: in equatorial latitudes it is less pronounced than in temperate or polar ones.[ ...]

Nutrition is one of the oldest connections of the body with the environment. Adaptation to its lack can also be behavioral. them, instinctive, and conditioned by the processes taking place on molecular level. The first is eating more food than the energy expenditure of the body requires. Excessively consumed food is converted into fat reserves, which are consumed under unfavorable conditions; for hunting. This is observed, for example, in coppers, whose females feed their young in winter without leaving the den. Other examples of instinctive adaptation to the lack of food are the storage of food for the winter by many rodents and various animal migrations (whether within their habitat, to more food-rich areas, or over long distances, like migratory birds). An essential way of adapting to the lack of food and water is the winter and summer sleep discussed earlier, which is associated not only with changes in the nature of nutrition, but also with seasonal fluctuations. temperature regime, length of daylight hours and other environmental conditions.[ ...]

At all stages of substantiation and decision-making on the use natural resources and the placement of energy facilities, analysis and assessment of the impact of the planned economic activity on the environment, including the ecology of adjacent areas, will be carried out. The developed programs for the development of the energy sector of the regions and the construction of new energy facilities must undergo a mandatory environmental review. At the same time, studies of the social consequences of the proposed activity must be carried out without fail, with an analysis of possible emergency situations, the definition of measures to prevent negative consequences in the near and long term and assessment of the degree of risk and reliability of objects. As a rule, new facilities of the fuel and energy complex will provide for a set of tools for environmental monitoring, in particular monitoring the state of hydrological systems, monitoring seismicity and hydrodynamics of oil and gas production areas, monitoring the migration of animals and birds, restoring their populations .

The content of the article

ANIMAL MIGRATION, regular movement of an animal population, during which individuals from one area of ​​\u200b\u200bhabitat move to another, but then return back. Such circular travel may be seasonal, like the spring or autumn migration of birds, or it may take a lifetime to complete, as is seen in some Pacific salmon. Animal migrations have a pronounced adaptive (adaptive) character and arose in the course of evolution in a variety of species. Examples are the seasonal movements of microscopic animals from the deep part of lakes to shallow waters associated with changes in water temperature, or the migration of whales that swim from the polar regions to the subtropics in autumn, where their cubs are born, and return back to cold waters at the end of spring.

It is practically impossible to find at least two species of animals migrating in exactly the same way. Some move alone, others only in groups. Some move at the same time very slowly, while others move very quickly and practically without stopping. For example, Arctic tern migrations are annual flights from areas close to the North Pole (only a few degrees away from it) to areas where Antarctic ice is already found. On the other hand, some frogs move only a few hundred meters during the year, separating the river from the nearest pond where they breed.

In addition to migrations, animal populations can also demonstrate other types of movements. Some animals lead a nomadic lifestyle, and their movements are random in nature and are determined by the specific conditions prevailing in certain places. For example, many of the large herbivores that live in herds on the plains of East Africa move around depending on the availability of food and climatic conditions in a particular area. These movements may take place along unsettled routes and are not associated with a mandatory return to the starting point.

Another type of population movement is the so-called. "Invasions" characteristic of some birds, mammals, as well as many insects. Invasions are usually observed in regions characterized by a harsh climate with sharp seasonal fluctuations. A well-known example is the brown lemming in the arctic tundra. During a 3–4-year cycle, the number of these animals increases, and after reaching a certain maximum, it quickly decreases. Upon reaching the peak of numbers, when the tundra is literally teeming with lemmings, they leave their native places en masse and go on a long journey. Very many fall prey to birds of prey and mammals, while most others die of disease and starvation, or drown in rivers and lakes or in the sea. However, some manage to survive a difficult time, and the population cycle begins again.

The polar owl, also living in the Arctic regions, preys not only on lemmings, but also on hares. In those rare winters when there are few lemmings and hares, the snowy owl moves south in search of prey, sometimes even reaching California.

Similar sudden invasions are sometimes observed in some seed-eating birds, usually staying in one area. For example, species living in the highlands or in northern latitudes, such as the Asian and North American nutcrackers, as well as the crossbill, in the years of poor seed harvests of conifers - their main food - show disorderly movements from northern latitudes to more southern latitudes or from mountainous regions to valleys.

Among insects, several species of locusts, found in Africa and Asia, have gained particular fame, and make mass flights when a very high population density is reached and there is a shortage of food. Moving to new areas, swarms of locusts can literally outshine the sun; only very few remain in the places where they were born.

Unlike invasions, many other movements made by populations are hardly noticeable. They occur slowly and sometimes lead to a change in the distribution area of ​​a particular species. Thus, over the past 30,000 years, man has migrated from Asia through the Bering Strait to North America, and then moved south as far as South America.

Food security.

The farther from the equator certain land animals live, the more noticeable seasonal fluctuations in their food supply. In the tropics, the amount of food available, although varying with the alternation of dry and rainy periods, remains fairly constant throughout the year as a whole. As you move north or south, seasonal changes begin to appear. For example, in the tropics, insectivorous birds have a more or less constant amount of food at their disposal, while those nesting in Alaska or northern Canada are faced with the fact that there is a lot of food in late spring - early summer and very little in late summer - early autumn; as a result, migration to the south from places that were so favorable during the nesting period becomes absolutely necessary for survival. During the winter months in northern North America and Eurasia, lakes, rivers, and mud flats are ice-bound, serving as the main feeding grounds for many waterfowl and marsh birds in the summer. It is not surprising that the flight to the south is absolutely obligatory both for these birds and for the various raptors hunting them.

Ecological analogs of insectivorous birds among mammals are small insectivorous bats, active (unlike birds) at night. In the northern latitudes, where it is cold in winter and there are no insects, many bats hibernate. Some species, such as the gray bat ( Lasiurus cinereus) and its close relative - red leather ( Lasiurus borealis), migrate south to warmer areas where they remain active throughout the winter.

Reproduction.

In many cases, the migration of animals is associated with the characteristics of reproduction. Some fish and marine mammals are examples. Various types of Pacific salmon fish of the genus Oncorhynchus spawn in the rivers of the west coast of North America and the east coast of Asia. To spawning grounds, they sometimes have to climb up the rivers a thousand kilometers from the mouth. After spawning, adults die, and fry hatched from eggs grow and gradually slide into the sea. This journey can last from several weeks to many months, but only once in the sea, the fish begin to properly fatten and grow very quickly. Having reached sexual maturity, which takes from one to several years (depending on the type of fish), they return to the very rivers where they were born. There they breed and die, repeating the fate of their parents.

Among marine mammals, gray whales demonstrate particularly impressive breeding migrations. During the summer months, they stay in the Arctic Ocean and the Bering Sea, where at this time there is an abundance of small marine organisms (plankton) - their main food. In autumn, having accumulated a large amount of fat, the whales begin to migrate south to warmer areas. Moving along the Pacific coast of North America, most whales reach shallow lagoons off the western shores of the Gulf of California, where they give birth to cubs. In March, males, as well as females without cubs, begin to migrate northward, and after a few weeks, females with cubs follow them along the same route. At the beginning of summer, they all reach the cold waters of the Arctic and Subarctic. The goal of the southward journey undertaken by the whales is to keep their young in warm water during the first few weeks of life, until they have formed a layer of fat that can reliably protect from the cold in the northern seas. The migration of whales to the north is primarily a return to places rich in food.

Climate and day length.

In the study of migration, it can be very difficult to separate the influence of climatic factors from those related to the supply of food or dictated by the characteristics of reproduction. The biological productivity that creates a food base for certain animals is itself largely determined by climate, and in areas far from the equator, the amount of food available often depends on temperature. For many organisms, the length of daylight is also very important, which regulates the normal reproduction cycle.

The amount of light received per day, the so-called. photoperiod, often directly stimulates the start of migration. In many birds, for example, the activation of the sex glands, as well as migratory activity, directly depend on the spring increase in the length of daylight hours.

Periodicity.

In some animals, migrations correlate with the lunar cycle. One of the most famous examples is the grunion ( Leuresthes tenuis) is a small fish that lives off the coasts of California and northwestern Mexico. From early spring to early autumn, she spawns on sandbanks, and spawning occurs only during especially high (syzygy) tides observed in the first three to four nights after the full moon or new moon. During spawning, which lasts 1–3 hours, females are thrown ashore by waves, where they dig a hole with their body movements, into which they lay eggs, which are immediately fertilized by males. The next surging wave carries the females back to the sea, and the juveniles hatch from the laid eggs already in the next spring tide.

Changes in the physiological state.

Changes in the physiological state of individuals are very often associated with migrations. In addition to the close relationship observed in spring between the increase in sexual activity and the degree of readiness for migration, both in spring and autumn, immediately before migration, there is a rapid increase in fat reserves necessary for energy supply for long flights. Some birds replenish their energy reserves by stopping to feed during their flight, but others cover vast distances with little or no stop. For example, in the golden plover ( Charadrius apricarius) the length of non-stop flight over water can reach 3200 km. Tiny red-throated hummingbird ( Archilochus colubris), living in the eastern regions of North America in the summer, spends the winter in Central America (from Mexico to Panama). In the fall, before migrating, these hummingbirds build up about two grams of fat - this is enough to cover more than 800 km without stopping over the waters of the Gulf of Mexico.

migratory routes.

When migrating, each population follows the same route, which requires certain means of orientation. For a long time, the mechanisms of animal navigation seemed mysterious, but in the course of recent research, some questions have been clarified. The first step was to determine the routes of movement of animals; various marking methods were used for this (such as ringing birds). If a sufficiently large number of animals were marked and then found in other places, then it is possible not only to trace the route of migration, but also to find out how quickly it occurs and what is the participation of individuals of different sexes and different ages in it.

Orientation to the sun and stars.

Vision is one of the main means by which migratory animals plot their route. Some familiar features of the landscape, such as mountain ranges, rivers, lake shores, or the outlines of sea coasts, can serve as landmarks. A certain role in orientation may also be played by the ability to recognize the position of the stars at night, and the position of the sun during the day.

The study of celestial orientation in animals began in the late 1940s with the work of the German ornithologist G. Kramer. Experimenting with migratory birds kept in captivity, he came to the conclusion that starlings, being diurnal migrants, are guided during their flights by the sun. A few years later, Franz and Eleanor Sauer were able to explain how birds that migrate at night find their way. Working with small passerines, they found that as long as the stars are not visible, the movements of birds are chaotic. Additional experiments carried out both in Europe and in America confirmed that many birds that are nocturnal migrants orient themselves by the stars during flight.

The ability to navigate by the sun and stars is not unique to birds. Experiments with one of the types of toads ( Bufo fowleri), living in the ponds of the central regions of the United States, showed that young, until recently former tadpoles, individuals always move towards the shore. If toads of this age are placed in a circular cage, from which only its walls, the sky and the sun not covered by clouds are visible, then they always move in a direction perpendicular to the line of their native coast. Even if these toads are moved to some other place and placed in the same cages, their movement will again be oriented in the same direction. Similar experiments with frogs, namely the cricket tree frog, have shown that they can navigate both by the sun and by the stars.

Orientation to the Sun was also found in white perch, a fish that lives in many freshwater lakes in North America. When the spawning period approaches, these fish from the open part of the lake move to the shore. If they are caught where they spawn and released in the same lake, but in the central part of it, they begin to move in the direction of the places where they were caught (this has been demonstrated using floats attached to their backs with thin nylon threads) .

Orientation with the help of smell.

Orientation, based on the perception of smells, is extremely important for many organisms, from insects to mammals. An example of this is the monarch butterfly, which makes large seasonal movements. In autumn, males are the first to set off along a strictly defined route; odorous glands on their wings leave an odor trail, which is used for orientation by females flying behind them. Having reached the wintering grounds, the butterflies accumulate on the trees in huge numbers, and in the spring they set off on their way back to the north.

Several species of Pacific salmon, returning from the sea to the very rivers where they were born, orient themselves with the help of the characteristic smell of the waters of their native river, imprinted in them from the first days after hatching from eggs. This odor is determined both by the minerals in the watershed and by the organic matter present in the waters of the river and giving it its chemical identity.

currents.

Currents play an important role in the life of animals living in the seas, as well as in rivers (especially where visibility is limited). Amazing migrations associated with ocean currents are made by European and American eels (representatives of the genus Anguilla). Those that live in Europe grow and mature in the rivers flowing into the Atlantic Ocean - from Scandinavia to the Iberian Peninsula. After spending 5 to 20 years there and reaching sexual maturity, they roll into the sea, then, drifting with the Canary and North Equatorial currents, cross the Atlantic Ocean and reach the Sargasso Sea - a specific area in the northwestern part of the Atlantic, where there are no currents and in abundance large algae floating near the surface develop. In these places, at great depths, eels multiply, after which they die. The hatched larvae rise to the surface and are transported with the waters of the Gulf Stream to the shores of Europe. This journey takes them three years, and by the end of it, the eels are already able to move up the river systems, where they remain until puberty. Similar migrations are made by American eels living in the rivers of the Atlantic coast.

Impending dangers.

Migration always requires the consumption of stored energy, and the amount of energy needed to cover long distances must be simply enormous. Therefore, migratory animals are always in danger of physical exhaustion. In addition, they easily fall prey to predators. Successful overcoming of the migration route to a very large extent also depends on climatic factors. The sudden onset of a cold front during the northward migration of birds in spring can have fatal consequences for many birds, and fogs and storms cause them to lose their bearings and go astray.

A serious danger for many migrants is a person. Knowing the routes of commercial animal species, people hunt them for food or for other purposes, including purely sporting ones. Various structures, such as television towers and skyscrapers, also cause the death of hundreds of thousands of birds. The blocking of rivers by dams creates obstacles for the rise of fish upstream to spawning grounds.

Animal migration is the movement of a population of animals from one place to another, associated with a change in climate conditions or with the period of their development. Gathering in herds and flocks, animals, birds or fish go on their journeys, captivating people with their beauty. Which, in fact, you can see in the photo.


1. Africa. Every year, more than 1 million white-bearded wildebeests and about 200,000 zebras migrate to the waters, covering a distance of 485 kilometers through Kenya and Tanzania.
2. One of the most impressive migrations belongs to crabs from Christmas Island. About 50 million red crabs live on this tiny piece of land in the Indian Ocean. Once a year they run to the water and come back.
3. This time, the black-browed albatrosses chose the Falkland Islands to mate. Mountain caracaras carefully observe everything that happens the whole winter, they wait until the birds, with a wingspan of more than 2 meters, begin to lay eggs and breed. Albatrosses never leave their eggs unattended: the female or male is always nearby.
4. Every year, millions of saucer-sized red crabs on Christmas Island run over the slopes, cliffs and mountains into the water.
5. A single monarch butterfly, on its own, can never cover the distance of their migration from Mexico to northern Canada and back. Therefore, they turned this relay race with the change of entire generations into a way of life.
6. The Pacific walrus, which is not physically predisposed to long-distance swims, uses drifting ice floes for rest and mating, making its way from the coast of Alaska to the coast of Russia and back. Unfortunately the ice Lately getting smaller and smaller...
7. Western Wyoming national park. Today, the migratory pronghorn herd numbers only 200 heads, which is incomparably less than before. Always the migration of these animals was not easy, but today, in order to descend from the mountains to the valleys, they need to overcome a large number of borders, channels, fences and other obstacles, which lead to a decrease in this, and so rare, species.
8. The longest land migration (490 km) belongs to rare species elephants of Mali. Still, without constantly moving from one source of food and food to another, it is simply impossible to survive in the Sahara Desert.
9. This is a frame from the movie “ national geographic» about the migration of zebras in Africa. A large number of young mothers usually do not stand such a long test.
10. Great white sharks cover thousands of miles every year, traveling from Hawaii to northern part Mexico.
11. Male sperm whales travel alone for most of their lives, overcoming hundreds of thousands of kilometers from ocean to ocean. But every year they sail to the Azores (Portugal) "to meet" with the same as they are, from where they go together to the females waiting for them.
12. Every day, adult red-eyed Rockhopper penguins descend to the sea to eat and again climb the steep cliffs where their chicks are hidden. After three months, the penguins return to the sea, preparing for the new season. While their chicks, in order to avoid death from albatrosses, try their wings and fly away from land. Many of them may not return there for more than 10 years.
13. Survival by yourself big fish in the sea, the whale shark, however contradictory it may sound, depends on microscopic plankton. It is these inhabitants of the seas that this huge creature feeds on.
14. Mississippi River. White pelicans breed in the summer in North America, and fly south for the winter, reaching Central America small flocks of 150-180 birds.
15. The migration of Pacific walruses directly depends on the movement of ice - in winter, when the ice expands, they swim to the south, and in spring and summer, when it breaks, they return back to the north.
16. An amazing migration can be observed on Lake Palau, where every day 5 million jellyfish follow: in the morning - strictly to the east, in the afternoon - to the west. At night, jellyfish dive up to 13 meters underwater, where they feed on the bacteria they need to survive.
17. Mexico, Michoacan: in a high-quality photo, the viewer can appreciate all the brightness and beauty of the migration of monarch butterflies.