Biological and geographical features of migration of terrestrial animals.

Introduction

Aerospace research methods - a variant of remote sensing methods, a system of methods for studying the properties of landscapes and their changes using helicopters, manned aircraft spaceships, orbital stations and special spacecraft, usually equipped with a variety of imaging equipment. There are visual, photographic, electronic and geophysical research methods. Application of A. m. and. speeds up and simplifies the mapping process and has great importance when organizing condition monitoring environment.

In some cases, direct satellite observations are used to monitor the migration of large animals, on whose bodies radio transmitters are mounted, transmitting information about the movement and condition of the animals.

migration animal aerospace observation

Animal migrations

MIGRATION OF ANIMALS, the relocation of animals to another habitat, caused by changes in living conditions in their previous habitats or changes in the animal’s requirements for these conditions at different stages of development (ontogenetic migrations). Exist various shapes migrations. For example, plankton makes daily migrations, moving vertically in the water column during the day as light levels and water temperature change; following it move organisms that are in a food relationship, for example. fish. Seasonal migrations occur in the fall when the food supply deteriorates, and also in the spring during the breeding season. They take place at approximately the same time, under certain conditions and along already known routes. There are vertical migrations performed by animals in mountains, soil and water bodies; latitudinal and meridional - in mammals and migratory birds. Migratory fish (salmon, sturgeon) perform anadromous migrations from seas to rivers and catadromous migrations from rivers to seas. Non-periodic migrations occur in extreme natural conditions: drought, fires, floods, eruptions, earthquakes, etc., as well as with an increase in population density (overpopulation). Such migrations can significantly change existing ecosystems.

The resettlement of animals is also possible with a change in lifestyle, for example. from sessile to mobile in coelenterates and barnacles; when changing the living environment, for example. in insects. Migration can drag on for years, for example, larvae of river eels, which spawn in the Sargasso Sea, return to the rivers of the basin for more than 4 years Baltic Sea. The study of animal migrations is carried out different ways- from tagging animals and monitoring them to using Earth's space satellites.

Mammal orientation

Since migration is one of the forms of development of the surrounding space, no Living being, who does not have the ability to navigate, is unable to master this space, cannot move in it in an environmentally expedient and useful way for himself. And if this is so, then, therefore, evolution migration behavior went, first of all, through improving the ability to navigate in space. But if migration is impossible without orientation, then the ability to navigate in space undoubtedly goes beyond the scope of migration tasks, ensuring the existence of a living organism in the surrounding world. The ability to perceive objects and phenomena in the environment and, on this basis, create an idea of one’s location in space is inherent in all animals and accompanies any animal organism from the moment of its birth until death.

The ability to navigate correctly is vital for all creatures, but it is especially important for migratory species. As a rule, they use noticeable landmarks, and then the ability to find the desired direction by the sun, moon or stars is not so necessary, becoming a valuable aid in critical situations, and in cases where travel is made over very long distances. An assistant in the orientation of animals during migration is not a mysterious “sense of direction”, but vision, memory and a sense of time.

The behavior of mammals differs from the behavior of birds and lower animals, primarily in that in mammals learning plays a greater role than instinct. Therefore, among mammals, the ability to navigate by position celestial bodies It is much less common, although many species have been specifically studied to identify such abilities. However, scientists have found that field mice, which to some extent are also characterized by daytime activity, are oriented by the sun. It is very likely that in large mammals, young animals can simply remember the path to follow during migration, learning from their parents and other members of their community, and then pass on this knowledge to subsequent generations. The assumption that the sense of smell plays a certain role in orientation in mammals has only recently been experimentally confirmed, and here we may be on the verge of interesting discoveries.

Smells and smell play a huge role in the lives of animals. Smells carry life necessary information from the surrounding world, excite instincts, conditioned reflexes, determine a positive or negative attitude towards new environmental factors. Smell is one of the most ancient and most important senses, with the help of which animals navigate their environment.

Ways to study migrations

Methods for studying mammal migration are varied and complex. This is primarily due to the fact that mammals live in different environments. Some of them live in terrestrial conditions in the forest and on the ground or in the crowns of trees. Many of these animals have excellent climbing ability. Other land animals inhabit open spaces and have running fast, or when danger arises, they immediately hide underground (marmots, gophers); some of the mammals (muskrat, mink, muskrat, nutria, etc.) lead semi-aquatic image living near rivers where they get food.

In recent years, migration has been addressed Special attention scientists all over the world. Migrations began to be studied not only through direct observations, but also through tagging. Already, tagging of many terrestrial animals gives interesting result and forces us to reconsider previous theories about their geographical location. Tagging is a more accurate and objective reflection of migrations occurring in nature.

Animal tagging began to be used in 1924. At the beginning (in 1924-30), only 22 animals were tagged: 19 hares, 2 chipmunks and 1 bat. These were uncertain steps in a new interesting business. Subsequently, animal tagging began to be introduced everywhere, and after 30 years, 16,693 animals belonging to 75 species were tagged.

V.S. Pokrovsky, an employee of the Environmental Protection Commission of the USSR Academy of Sciences, noted back in 1959 that this type of research in our country lags significantly behind others, because The method of capturing and tagging mammals is still poorly developed.

At the first stage of tagging development, most fur-bearing animals were tagged. Of the 16,693 heads ringed between 1924 and 1955, there were 11,248. Very few ungulates and mouse-like rodents have been tagged, although their migrations are of great scientific interest. When comparing the development of animal banding with similar work on birds carried out over the same period, we can say that the results obtained for mammals are insignificant.

Tagging animals is a complicated matter. Caught live animals are usually very aggressive. Scientists are currently testing different narcotic drugs, temporarily putting animals to sleep, especially large terrestrial ones, so that various manipulations can be carried out with them during tagging. This idea comes from the experience of hunters of many tribes of the Southern Hemisphere, who used poisoned arrows for hunting. A drug called curarediplocin has already been created, which has strong effect on the animal’s muscles, temporarily relaxing it. The use of this invention can facilitate mass tagging of deer, wild ass and other ungulates and intensify the study of the migrations of these animals. Various approaches to tagging are also determined by the morphological characteristics of mammals. Land animals have auricles that are heavily used for marking. Underground and aquatic animals do not have them.

Marking methods:

Tattoo . The animal's ear is first wiped with alcohol, then a number is placed with tattoo pliers and mascara is rubbed into the puncture sites, which is usually well preserved.

Banding. For animals that lack an ear (muskrat, shrew), the ring is placed on the hind leg, above the foot.

Cutting or punching. Using special pliers, marks are made on the ears and membranes of the paws, giving each mark a conditional numerical value. Used in the study of semi-aquatic animals (mink, otter).

If banding is carried out on a large scale, then this method allows one to draw some conclusions about the general reserves of game in a given area, because the number of all individuals killed by hunters should be approximately the same percentage of the total number of this game in a given area as the percentage of prey of ringed individuals to the number of rings worn: a/b = x/c, where a is the number of ringed birds, b - number of returned rings, c - the total number of individuals of the species killed by hunters.

Methodological difficulties in studying animal migrations lie in the fact that they to varying degrees are accessible to direct human observation due to their secretive lifestyle; Usually all animals quickly leave when they meet a person, and long-term, direct observation of them in natural conditions is almost impossible.

We know a lot about the migration of animals from the works of Russian travelers of the 18th century, academicians I. Lepekhin, P. Pallas and the 19th century A.F. Middendorf and others. During their travels, they paid great attention to the relocation of animals.

To clarify the directions and routes of migration, it is important to return tags or report the tag of hunted animals.

Labeling is important scientific method migration studies.

Migration (from Latin migrans) means relocation. Migrations are widespread among animals all over the globe and represent an interesting adaptation to the transfer of favorable conditions, which sometimes occur in nature.

In autumn, as feeding conditions worsen, the bulk of arctic foxes and reindeer migrate from the tundra to the south, into the forest-tundra and even into the taiga, where it is easier to obtain food from under the snow. Following the deer they migrate south and tundra wolves. In the northern regions of the tundra, white hares undertake mass migrations to the south at the beginning of winter, and in the opposite direction in the spring. migration seasonal relocation animal

Migrations of animals occur when different conditions and they pass differently.

Regular seasonal migrations of desert ungulates also depend on seasonal changes in vegetation cover, and in some places, on the nature of the snow cover. In Kazakhstan, saigas often live in the northern clayey semi-desert steppes in the summer; in winter they migrate to the south, to the area of less snowy wormwood-fescue and wormwood-hodgepodge semi-deserts.

In general, migration is characteristic of a relatively smaller number of species among mammals than among birds and fish. They are most developed in sea animals, bats and ungulates, while among the species of the most numerous groups - rodents, insectivores and small predators- there are practically none.

Animals have periodic migrations, they are also called evictions. Periodic evictions - migrations include those that represent a massive departure of animals from breeding grounds without subsequent return to their former habitats. According to science, such evictions are caused by a sharp deterioration living conditions, as well as lack of food, which is associated with the emerging high population density of the species, forest and steppe fires, severe droughts, floods, excessive snowfall, and other reasons. From this it can be seen that numerous circumstances can cause masses of animals to move over long distances. Invasions are the movement of animals outside their homeland. Such movements differ from true migrations in their irregularity and large intervals between successive invasions. Sometimes they are considered as the initial stages of the formation of real migrations, arising from explosive settlements - “emigrations”. Infestation is like a safety valve triggered by excessive population density. This in itself favors the existence of the species only in an indirect way. Under normal natural conditions, population processes are in equilibrium, and population growth, leading to eviction, rarely occurs. Invasion is a phenomenon whose disadvantages are striking, but at the same time, over a long period of time, it provides an advantage that more than outweighs the disadvantages. A typical example of these migrations is the migration of lemmings and squirrels. Irreversible periodic migrations are characteristic common squirrels. They (migrations) occur quickly in response to emerging unfavorable conditions. Migrations begin in July-August, when squirrels begin to feed on seeds and nuts from the fresh harvest and discover their deficiency. Migrations last about 6 months. Squirrels sometimes travel up to 500 km or more. Squirrels do not migrate in groups, but singly. The wanderings of squirrels repeat periodically every 4-5 years and greatly influence the yield of fur and the economy of squirrel hunters. The speed of squirrels during migration reaches 3-4 km/h.

Animals make seasonal migrations annually and in certain time of the year. These migrations are regular and reversible. Animals, leaving their breeding places, return to the same places when favorable conditions arise. Seasonal migrations are characteristic of the Arctic fox, the main reason for which is food. Arctic foxes follow migrating lemmings, completely repeating the characteristics of their migrations. The migration of predatory animals is mainly associated with the migration of small animals, which provide food for predators.

Seasonal migrations are especially clearly manifested in places with a sharp change in living conditions from winter to summer, in places with harsh winter and hot, dry summers. This phenomenon has the character of a purposeful mass movement, although it is not always clearly visible. The reasons that cause seasonal migrations are always complex. However, the most noticeable of them is hunger. Another reason is the attack on animals by midges: mosquitoes, gadflies, horseflies.

Seasonal migrations, in turn, are divided into horizontal and vertical.

Horizontal migrations mean those when animals move from one place to another, changing environmental conditions within their typical landscape. Such migrations are typical for reindeer, cats and other animals.

Vertical migrations are understood to be those when animals, in the same season of the year, find better conditions in the spring in high mountainous areas on alpine meadows, and in the fall they descend to foothill pastures. Such movements are typical for mountain inhabitants - goats, chamois and other ungulates. By summer, mountain ungulates rise to the upper zones of the mountains with their rich grass stand, but in winter, as the depth of the snow cover increases, they descend. And in this case, some predators, such as wolves, are observed combined with ungulates.

Diurnal migrations are also known among animals - this is the transition of animals from daytime resting places to places of watering places, salt licks and feeding grounds. Diurnal migrations are typical for hares, deer and other animals.

All of the above-mentioned migrations are called active because the animals carry them out with great excitement; they sometimes appear in populated areas and in other places that are not typical for their habitat and often, unfortunately, remain unaccounted for.

In contrast to active migrations, passive migrations are also observed among animals, i.e., those when animals move away from their breeding grounds and usual habitat with the help of ice or water flow. For example, the migrations of walruses, polar bears, and arctic foxes that got onto ice floes and were carried by the current into the ocean to some islands are known. During high water, hares and muskrats, falling on floating objects or ice floes, descend long distances downstream. Different modes of transport play a significant role in passive migration. Particularly characteristic is settlement through vehicles mouse-like rodents. As a result of passive migrations, house mice, rats and other animals were settled almost all over the world. Many of the introduced animal species get along well in new places. Thus, the range of certain species of harmful rodents increases.

Migrations of rodents are of interest in the sense that many of them can be used in hunting and fishing and in the fight against agricultural pests.

ANIMAL MIGRATION
regular movement of a population of animals, during which individuals move from one habitat to another, but then return back. Such a journey along a circular route can be seasonal, like the spring or autumn migration of birds, or it can require a lifetime to complete, as is observed in a number of Pacific salmon. Animal migrations have a pronounced adaptive character and arose in the process of evolution among the most different types. Examples include the seasonal movements of microscopic animals from the deep parts of lakes to shallow waters associated with changes in water temperature, or the migration of whales, which in the fall swim from the polar regions to the subtropics, where their calves are born, and in late spring return back to cold waters. It is almost impossible to find at least two species of animals that migrate in exactly the same way. Some move alone, others only in groups. Some move very slowly, while others move very quickly and practically without stopping. For example, the migrations of Arctic terns are annual flights from areas close to North Pole(distant from it only a few degrees), to areas where they are already found Antarctic ice. On the other hand, some frogs move only a few hundred meters throughout the year, separating the river from the nearest pond where they breed. In addition to migrations, animal populations can exhibit other types of movements. Some animals lead a nomadic lifestyle, and their movements are random character and are determined by the specific conditions prevailing in certain places. For example, many large herbivores living 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 occur along unsettled routes and are not associated with a mandatory return to the original location. Another type of population movement is the so-called. "invasions" characteristic of some birds, mammals, and 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 the 3-4 year cycle, the number of these animals increases, and having reached a certain maximum, it quickly falls. Upon reaching the peak of their numbers, when the tundra is literally teeming with lemmings, they leave their native places en masse and go on a long journey. Many people become victims birds of prey and mammals, while most others die from disease and exhaustion or drown in rivers and lakes or in the sea. However, some manage to survive the difficult time, and the population cycle begins again. The polar owl, which also lives in the Arctic regions, hunts not only lemmings, but also 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, which usually stay in one area. For example, those living in the highlands or in northern latitudes Species such as the Asian and North American nutcrackers, as well as the crossbill, in years of poor harvest of coniferous seeds - their main food - demonstrate disordered movements from northern latitudes to more southern latitudes or from mountainous regions to valleys. Among insects, several species of locusts are especially famous, found in Africa and Asia and making mass migrations in cases where very high population densities are reached and there is a shortage of food. As they move into new areas, swarms of locusts can literally outshine the sun; only a very few remain in the places where they were born. Unlike invasions, many other movements made by populations are little noticeable. They occur slowly and sometimes lead to changes in the area of distribution of a particular species. Thus, over the past 30,000 years, humans have migrated from Asia through the Bering Strait to North America, and then moved south all the way to South America.
Food supply. The further from the equator certain land animals live, the more noticeable are the seasonal fluctuations in their food supply. In the tropics, the amount of food available, although variable depending on the alternating periods of drought and rain, generally remains fairly constant throughout the year. As you move north or south, seasonal changes begin to appear. For example, in the tropics, insectivorous birds have at their disposal a more or less constant amount of food, 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 areas that were so favorable during the nesting period becomes absolutely necessary for survival. IN winter months in the north North America and Eurasia, ice binds lakes, rivers and mudflats, which served as the main feeding grounds for many waterfowl and wading birds in the summer. It is not surprising that the flight to the south is absolutely mandatory both for these birds and for the various feathered predators that hunt them. Ecological analogues insectivorous birds among mammals are small insectivorous bats, active (unlike birds) at night. In northern latitudes, where winter is cold and there are no insects, many bats hibernate. Some species, such as the gray bat (Lasiurus cinereus) and its close relative- red leatherback (Lasiurus borealis), migrate south, to more warm areas, where they remain active throughout the winter.
Reproduction. In many cases, the migration of animals is associated with the characteristics of reproduction. An example is some fish and marine mammals. Different kinds Pacific salmon fish The genus Oncorhynchus spawns in rivers on the west coast of North America and the east coast of Asia. To reach their spawning sites, they sometimes have to climb up rivers a thousand kilometers from the mouth. After spawning, the adults die, and the fry that hatch from the eggs grow and gradually slide into the sea. This journey can last from several weeks to many months, but only once at sea do the fish begin to fatten up properly 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 reproduce and die, repeating the fate of their parents. Among marine mammals Gray whales exhibit particularly impressive breeding migrations. 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 the fall, having accumulated a large number of fat, 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 their calves. In March, males, as well as females without cubs, begin to migrate north, and a few weeks later, 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 whales' journey to the south is to keep their calves in warm water during the first few weeks of life, until they developed a layer of fat that could reliably protect them from the cold in northern seas. The migration of whales to the north is, first of all, a return to places rich in food.
Climate and length daylight hours. When studying migrations, it can be very difficult to separate the influence of climatic factors from those related to food availability or dictated by reproductive characteristics. Biological productivity, which creates a food supply for certain animals, is itself largely determined by climate, and in areas far from the equator, the amount of available food often depends on temperature. For many organisms, the length of daylight is also very important, which regulates the normal reproductive cycle. The amount of light received per day, the so-called. photoperiod often directly stimulates the onset of migration. In many birds, for example, activation of the gonads, as well as migratory activity, directly depend on the spring increase in daylight hours.
see also BIRDS .
Periodicity. In some animals, migrations correlate with lunar cycle. One of the most famous examples- grunion (Leuresthes tenuis) is a small fish that lives off the coast of California and northwestern Mexico. WITH early spring until the beginning of autumn, it spawns on sandbanks, and spawning occurs only during particularly high (syzygy) tides, observed in the first three to four nights after the full or new moon. During spawning, which lasts 1-3 hours, females are thrown ashore by waves, where they use body movements to dig out a hole in which they lay eggs, which are immediately fertilized by males. The next surging wave carries the females back to the sea, and juveniles hatch from the laid eggs already at the next spring tide.
Changes in physiological state. Migration is often associated with changes in the physiological state of individuals. In addition to the close relationship observed in the spring between the increase in sexual activity and the degree of readiness for migration, both in the spring and in the fall, 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 migration, but others travel vast distances almost without stopping. For example, the golden plover (Charadrius apricarius) can fly non-stop over water for up to 3,200 km. The tiny ruby-throated hummingbird (Archilochus colubris), which summers in eastern North America, spends the winter in Central America (from Mexico to Panama). In the fall, before migrating, these hummingbirds gain about two grams of fat—enough to cover more than 800 kilometers of water across the Gulf of Mexico without stopping.
Migration 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 cleared up some questions. The first step was to determine the movement routes of the animals; used for this various methods tagging (such as bird ringing). 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 by the sun and stars. Vision is one of the main means by which migrating animals navigate their route. The landmarks can be some familiar landscape features, such as mountain ranges, rivers, lake shores, or the outlines of sea coasts. The ability to recognize the position of the stars at night and 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, navigate by the sun during their flights. A few years later, Franz and Eleanor Sauer were able to explain how birds migrating at night find their way. Working with small passerines, they discovered that until the stars were visible, the birds' movements were chaotic. Additional experiments conducted both in Europe and America confirmed that many birds that are nocturnal migrants navigate by the stars during flight. The ability to navigate by the sun and stars is not unique to birds. Experiments with a species of toad (Bufo fowleri) living in ponds central regions The USA have shown that young individuals that were recently tadpoles 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 shore. 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, showed that they can navigate by both the sun and the stars. Solar orientation has also been found in white perch, a fish that lives in many freshwater lakes in North America. When the spawning period approaches, these fish move from the open part of the lake to the shore. If they are caught where they spawn and released into 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 using smell. Orientation based on the perception of odors is extremely important for many organisms - from insects to mammals. An example of this is the monarch butterfly, which makes large seasonal movements. In the fall, males are the first to set off along a strictly defined route; scent glands on their wings leave a scent trail, which is used for orientation by females flying behind them. Having reached their wintering grounds, the butterflies accumulate on trees in huge numbers, and in the spring they begin their return journey to the north. Several species of Pacific salmon, returning from the sea to the very rivers where they were born, navigate using the characteristic smell of the waters of their native river, which is imprinted on them from the first days after hatching from the eggs. This odor is determined both by the minerals in the catchment area and organic substances, present in the waters of the river and giving it its chemical identity.
Currents. Currents play an important role in the lives of animals living in the seas, as well as in rivers (especially where visibility is limited). Amazing migrations associated with ocean currents, are committed by European and American eels (representatives of the genus Anguilla). Those that live in Europe grow and mature in 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 Sargasso Sea- a specific area in the northwestern part of the Atlantic, where there are no currents and large algae floating near the surface develop in abundance. In these places at great depths, eels reproduce and then 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. river systems where they remain until puberty. American eels living in the rivers of the Atlantic coast make similar migrations.
Lurking dangers. Migration always requires the expenditure of stored energy, and the amount of energy required to cover long distances must be enormous. Therefore, migrating animals are always at risk of physical exhaustion. In addition, they easily become victims of predators. Successful completion of the migration route also depends to a very large extent on climatic factors. The sudden arrival of a cold front during the spring migration of birds to the north can have fatal consequences for many birds, and fog and storms cause them to become disoriented and lose their way. Humans pose a serious danger to many migrants. 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. Blocking rivers with dams creates obstacles for fish moving upstream to their spawning grounds.
See also BIOLOGICAL RHYTHMS.
LITERATURE
Cloudsley-Thompson D. Animal migrations. M., 1982

Collier's Encyclopedia. - Open Society. 2000 .

See what “ANIMAL MIGRATION” is in other dictionaries:

- (from Latin migrans) regular movement of a population of animals, during which individuals from one habitat move to another, but then return back. Migrations are most common in birds (bird migration) 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 living conditions in their habitats or associated with their development cycle. There are random... ... Ecological dictionary

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

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 Guide

animal migration- gyvūnų migracija statusas T sritis ekologija ir aplinkotyra apibrėžtis Gyvūnų kėlimasis iš vienų vietų į kitas, susijęs su aplinkos sąlygų kitimu. Yra reguliarioji (sezono, paros) ir nereguliarioji (per sausras, potvynius ir kt.). atitikmenys:… … Ekologijos terminų aiškinamasis žodynas

What causes animal migrations? What are the types of movement of fauna representatives? What are the reasons for this behavior? We will consider the answers to these and other questions in our publication.

Types of migrations

Researchers identify several types of movements of fauna representatives:

Seasonal.
Periodic.
Age.

What is each type of migration? Let's consider each option separately. Thus, seasonal migrations of animals are caused by the need to search for better conditions for reproduction and raising offspring. For this reason, with the arrival of winter, many birds move to areas with a warmer, milder climate.

If we talk about periodic migrations, a striking example here is the behavior of fish. IN warm weather they prefer to live in fairly shallow bodies of water, spending most of their time close to the surface. As temperatures drop, fish leave their familiar territories, trying to move to deeper areas.

Periodic migrations of animals are also observed among predators. For example, bears that live in North America leave inhabited forests, concentrating near rivers where large schools of salmon come. These animals follow their food source until it finally runs out. Some whales also do the same, summer time swim from cold waters northern regions to the warm zones of the Atlantic, where large swarms of plankton are hunted.

As noted above, there are also age-related migrations of animals. The essence of such processes is as follows. Some representatives of the fauna lead a solitary, isolated life, controlling vast territories. During the mating season, such animals leave their usual habitats, returning back after mating. When young individuals are born, they leave the group upon reaching a certain age, after which they occupy new territories. The process is then repeated cyclically.

How were migration routes formed?

Researchers associate the emergence of animal migration routes, first of all, with climate changes that have occurred over many millennia. In ancient times, the movements of creatures occurred during the advance of glaciers or in the event of transformation certain territories to the barren lands. For example, it is surprising that some birds still cross deserts in their driest areas. However, there are safer and shortcuts achieving the goal of the trip. This behavior can be explained by the presence of genetic memory in birds. Probably, the ancestors of birds moved along these routes when the deserts were not yet so barren.

According to some scientists, the formation of migration routes is associated with the split of the earth's crust into separate continents, which drifted relative to each other. However, this theory was never confirmed, since such geological processes took much longer compared to evolutionary changes individual animals.

What causes animals to form groups before migrating?

With the onset of the period of migration of wild animals, changes occur in their bodies at the physiological and hormonal level. Species that usually lead isolated lives, jealously defending their territory, noticeably reduce the level of aggressiveness. This is due to an increased likelihood of survival as part of a group, as well as better orientation in unfamiliar terrain. Animals often form mixed packs, which include separate classes of creatures. Many birds and artiodactyls behave in a similar way.

How do animals navigate unfamiliar terrain?

Animal migrations are often accompanied by the need to overcome significant distances. How do they manage not to get lost when moving in unfamiliar latitudes? Often this is facilitated by a developed sense of smell. For example, monarch butterflies engage in large seasonal migrations. The males of such insects are the first to set off on the road. Their bodies have specific secretory glands that produce odorous substances. Using such trails as a guide, female butterflies migrate.

If we talk about fish of the salmon family, with the onset of the mating season, they return from the oceans to their places of birth, analyzing the smell and chemical composition waters of native rivers. Such information is stored in their memory at the moment they emerge from the eggs.

As for migratory birds, during the daytime they rely on the location of the sun, and when night falls, the starry sky becomes a kind of map for them. There are birds that remember routes that run along textured reliefs, in particular river valleys, coastlines, mountain ranges.

Some types of living beings can recognize infrared radiation, sense the planet’s magnetic field, and navigate by changes in level atmospheric pressure. The study of such incredible animal abilities contributed to the invention of a number of navigation devices by mankind.

What factors give impetus to migration?

An interesting question is how animals receive the signal to set off. Several factors come into play here. What matters is the change in the ratio between the duration of the dark and light periods of the day. In addition, a decrease in the amount of food, as well as a change in the temperature of the surrounding space, plays a role.

Migration for breeding purposes

In most cases, the reason for the migration of animals is the specific characteristics of procreation. A striking example serves as a way of life for some marine mammals and fish. Thus, salmon spawning occurs in the upper reaches of rivers in North America. They have to get here from the ocean, going upstream. At the end of the mating season, adults die. The fry that emerge from the eggs are gradually carried back into the ocean by the current. Only once in salty waters do young salmon begin to actively obtain food, develop and gain weight. Upon reaching sexual maturity, these fish repeat the fate of their parents.

Such large mammals, like gray whales, also migrate for breeding purposes. Having accumulated a significant amount of fat in summer period, with the arrival of autumn they move from the Arctic Ocean to the shallow lagoons in western California. It is here that whales give birth to their offspring, which are raised in safer climatic conditions.

Lack of food

Another reason for migration is food shortage. The greater the distance from equatorial zone animals live, the more often they experience problems finding prey. The result is the need to move to warmer climes for survival. This determining factor is predominantly for birds. Many species of birds are not able to obtain the required amount of food during periods when bodies of water are covered with ice.

Among mammals, some bats, whose prey are insects, migrate in search of food. Most of these animals go into seasonal hibernation with the arrival of cold weather. However, there are bats that migrate south, remaining active throughout the winter.

Changing the length of daylight hours

The migration of animals in Africa and other parts of the world often depends on climatic factors. The biological activity of mammals is affected by a reduction in daylight hours. At the same time, the level of available food supply is also decreasing. In some creatures, when this factor comes into effect, the work of the gonads is activated, which forces them to change their inhabited habitats to more fertile lands where long duration daylight hours. The main goal Such a movement results in the same increase in the probability of survival of the offspring.

Dangers that await animals during migration

Great animal migrations require creatures to expend significant amounts of energy. Its reserves are necessary to cover significant distances. Sometimes a long journey leads to physical exhaustion. Thus, animals often become prey to predators or die without being able to find enough food.

Successful migration also depends on climatic conditions. The sudden occurrence of certain atmospheric phenomena. For example, storms and fogs can cause loss of orientation in space. As a result migratory birds may go astray. Often the influence of such factors causes their death. But in some cases, this contributes to the settlement of animals in unfamiliar areas.

Human activity poses a certain danger to animals during migration. Focusing on the routes of movement of fauna representatives, people organize fishing and hunting. A person is not always driven by the need to obtain food. Sometimes purely sporting interest comes into play. Significant problems for fish during migration are created by dams that do not allow reaching spawning grounds. The construction of high-rise buildings and television towers interferes with the orientation of birds in space, and leads to their death.

Finally

So we found out what kinds of animals exist. We figured out what makes them exhibit this behavior. Finally, I would like to note that scientists have not yet fully studied the issue of migration of living beings. In particular, the mechanisms of orientation of fauna representatives when moving through unfamiliar terrain remain not entirely clear to biologists. To uncover such mysteries of nature, researchers resort to methods of animal tagging, visual observation, and artificial imitation of certain situations.

Meaning of ANIMALS MIGRATION in Collier's Dictionary

MIGRATION OF ANIMALS

regular movement of a population of animals, during which individuals move from one habitat to another, but then return back. Such a journey along a circular route can be seasonal, like the spring or autumn migration of birds, or it can require a lifetime to complete, as is observed in a number of Pacific salmon. Animal migrations have a pronounced adaptive character and arose in the process of evolution in a wide variety of species. Examples include seasonal movements of microscopic animals from the deep parts of lakes to shallow waters associated with changes in water temperature, or the migration of whales, which in the fall swim from the polar regions to the subtropics, where their calves are born, and in late spring return back to cold waters.

It is almost impossible to find at least two species of animals that migrate in exactly the same way. Some move alone, others only in groups. Some move very slowly, while others move very quickly and practically without stopping. For example, the migrations of Arctic terns 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 throughout the year, separating the river from the nearest pond where they breed.

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

Another type of population movement is the so-called. "invasions" characteristic of some birds, mammals, and 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 the 3-4 year cycle, the number of these animals increases, and having reached a certain maximum, it quickly falls. Upon reaching the peak of their numbers, when the tundra is literally teeming with lemmings, they leave their native places en masse and go on a long journey. Many fall prey to birds of prey and mammals, while most others die from disease and exhaustion, or drown in rivers and lakes or at sea. However, some manage to survive the difficult time, and the population cycle begins again.

The polar owl, which also lives in the Arctic regions, hunts not only lemmings, but also 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, which usually stay in one area. For example, species living in the highlands or northern latitudes, such as the Asian and North American nutcrackers, as well as the crossbill, in years of poor harvest of coniferous seeds - their main food - demonstrate disordered movements from northern latitudes to more southern ones or from mountainous regions to valleys.

Among insects, several species of locusts are especially famous, found in Africa and Asia and making mass migrations in cases where very high population densities are reached and there is a shortage of food. As they move into new areas, swarms of locusts can literally outshine the sun; only a very few remain in the places where they were born.

Unlike invasions, many other movements made by populations are little noticeable. They occur slowly and sometimes lead to changes in the area of distribution of a particular species. Thus, over the past 30,000 years, humans have migrated from Asia through the Bering Strait to North America, and then moved south all the way to South America.

Food supply. The further from the equator certain land animals live, the more noticeable are the seasonal variations in their food supply. In the tropics, the amount of food available, although variable depending on the alternating periods of drought and rain, generally remains fairly constant throughout the year. As you move north or south, seasonal changes begin to appear. For example, in the tropics, insectivorous birds have at their disposal a more or less constant amount of food, 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 areas that were so favorable during the nesting period becomes absolutely necessary for survival. During the winter months in northern North America and Eurasia, ice freezes the lakes, rivers, and mudflats that served as primary feeding grounds for many waterfowl and wading birds in the summer. It is not surprising that the flight to the south is absolutely mandatory both for these birds and for the various feathered predators that hunt them.

The ecological analogues of insectivorous birds among mammals are small insectivorous bats, active (unlike birds) at night. In northern latitudes, where winter is cold and there are no insects, many bats hibernate. Some species, such as the gray bat (Lasiurus cinereus) and its close relative the red bat (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. An example is some fish and marine mammals. Various species of Pacific salmonids of the genus Oncorhynchus spawn in rivers along the west coast of North America and the east coast of Asia. To reach their spawning sites, they sometimes have to climb up rivers a thousand kilometers from the mouth. After spawning, the adults die, and the fry that hatch from the eggs grow and gradually slide into the sea. This journey can last from several weeks to many months, but only once at sea do the fish begin to fatten up properly 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 reproduce and die, repeating the fate of their parents.

Among marine mammals, gray whales exhibit 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, 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 their calves. In March, males, as well as females without cubs, begin to migrate north, and a few weeks later, 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 whales' journey to the south is to keep their calves in warm water for the first few weeks of life, until they have formed a layer of fat that can reliably protect them from the cold in the northern seas. The migration of whales to the north is, first of all, a return to places rich in food.

Climate and length of daylight hours. When studying migrations, it can be very difficult to separate the influence of climatic factors from those related to food availability or dictated by reproductive characteristics. Biological productivity, which creates the food supply 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 reproductive cycle.

The amount of light received per day, the so-called. photoperiod often directly stimulates the onset of migration. In many birds, for example, activation of the gonads, as well as migratory activity, directly depend on the spring increase in daylight hours. See also BIRDS.

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

Changes in physiological state. Migration is often associated with changes in the physiological state of individuals. In addition to the close relationship observed in the spring between the increase in sexual activity and the degree of readiness for migration, both in the spring and in the fall, 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 migration, but others travel vast distances almost without stopping. For example, the golden plover (Charadrius apricarius) can fly non-stop over water for up to 3,200 km. The tiny ruby-throated hummingbird (Archilochus colubris), which summers in eastern North America, spends the winter in Central America (from Mexico to Panama). In the fall, before migrating, these hummingbirds gain about two grams of fat—enough to cover more than 800 kilometers of water across the Gulf of Mexico without stopping.

Migration 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 recent research has clarified some questions. The first step was to determine the movement routes of the animals; For this purpose, various tagging methods were used (such as bird ringing). 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 by the sun and stars. Vision is one of the main means by which migrating animals navigate their route. The landmarks can be some familiar landscape features, such as mountain ranges, rivers, lake shores, or the outlines of sea coasts. The ability to recognize the position of the stars at night and 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, navigate by the sun during their flights. A few years later, Franz and Eleanor Sauer were able to explain how birds migrating at night find their way. Working with small passerines, they discovered that until the stars were visible, the birds' movements were chaotic. Additional experiments conducted both in Europe and America confirmed that many birds that are nocturnal migrants navigate 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 in the central regions of the United States, showed that young individuals that were recently tadpoles 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 shore. 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, showed that they can navigate by both the sun and the stars.

Solar orientation has also been found in white perch, a fish that lives in many freshwater lakes in North America. When the spawning period approaches, these fish move from the open part of the lake to the shore. If they are caught where they spawn and released into 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 using smell. Orientation based on the perception of odors is extremely important for many organisms - from insects to mammals. An example of this is the monarch butterfly, which makes large seasonal movements. In the fall, males are the first to set off along a strictly defined route; scent glands on their wings leave a scent trail, which is used for orientation by females flying behind them. Having reached their wintering grounds, the butterflies accumulate on trees in huge numbers, and in the spring they begin their return journey to the north.

Several species of Pacific salmon, returning from the sea to the very rivers where they were born, navigate using the characteristic smell of the waters of their native river, which is imprinted on them from the first days after hatching from the eggs. This smell is determined both by the minerals in the catchment and by the organic substances present in the river waters that give it its chemical identity.

Currents. Currents play an important role in the lives of animals living in the seas, as well as in rivers (especially where visibility is limited). European and American eels (representatives of the genus Anguilla) perform amazing migrations associated with ocean currents. Those that live in Europe grow and mature in 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 abundance Large algae floating near the surface develop. In these places at great depths, eels reproduce and then 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 the onset of sexual maturity. American eels living in the rivers of the Atlantic coast make similar migrations.

Lurking dangers. Migration always requires the expenditure of stored energy, and the amount of energy required to cover long distances must be enormous. Therefore, migrating animals are always at risk of physical exhaustion. In addition, they easily become victims of predators. Successful completion of the migration route also depends to a very large extent on climatic factors. The sudden arrival of a cold front during the spring migration of birds to the north can have fatal consequences for many birds, and fog and storms cause them to become disoriented and lose their way.

Humans pose a serious danger to many migrants. 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. Blocking rivers with dams creates obstacles for fish moving upstream to their spawning grounds. See also BIOLOGICAL RHYTHMS.

Collier. Collier's Dictionary. 2012