Animal migration: types, causes and examples. Coursework: Biological and geographical features of land animal migration What is animal migration definition

Large-scale animal migrations are some of the most amazing events in nature. Some animals travel migratory routes with wings, fins or hooves in search of new habitats only on the verge of strength and survival.

Migration also plays a vital role in natural ecosystems, the veins and arteries of Mother Earth, while being a reminder of the interconnectedness of the world's habitats. We present to the attention of readers descriptions of the largest animal migrations on our planet.

These charming ocean wanderers make incredible migrations on the high seas. Some leatherback turtles are known to have crossed the Pacific Ocean between Indonesia and the United States - a vast distance of more than 20,000 kilometers - in 647 days. One of the most impressive features of these animals is the ability to find the beach where they were born in order to lay their eggs there.

While many of the world's marine mammal species are migratory, none travel as far as the giant right whale.

The gray whale (travels 22.5 thousand kilometers annually) and the humpback whale (swims 25.5 thousand kilometers each year) migrate the longest distance among all mammals on Earth.

These species swim to warmer tropical waters during the winter to find a mate and give birth to young. On the summer time they sail away to the richer arctic and ant arctic waters for food.

Dragonflies are capable of long-distance migrations, but until recently, scientists had no idea how far they could travel. In 2009, researchers discovered a 14,000 to 18,000-kilometer dragonfly migration route through India, the Maldives, and Seychelles, Mozambique, Uganda and ended at the point of departure.

Incredibly, this epic migration requires four generations of dragonflies, with each generation playing its part in a relay race-like journey. Undoubtedly, this is the longest migration of insects, known to science. It turns out that dragonflies follow the rains, from the monsoon period in India to the rainy season in East and South Africa.

Perhaps the most famous animal migration is the journey of millions of African wildebeest herds, who annually move in search of greener pastures.

Wildebeest do not travel alone. They are joined by as many as 200,000 zebras and 500,000 gazelles, followed by some of the top predators of the savannah. Such a migration is one of the grandest spectacles in the natural world, as herds cross crocodile-filled rivers while lions skulk in the tall grass nearby.

The vast savannahs of Africa could not exist without migration, and the maintenance of these habitat corridors is essential to the existence of these areas and the creatures that inhabit them.

Birds of about 1800 species are migratory. Some journeys are among the longest in the world.

The little arctic tern (pictured above) makes the longest migration in the world, traveling about 70,000 kilometers a year and zigzagging between the Arctic and Antarctic. (The gray petrel also deserves a mention, covering a similar distance.) Seabirds like albatrosses spend more time in flight than at rest, and bartail godwit undertakes the longest non-stop flight of any bird between New Zealand and China.

Mention should also be made of penguins making amazing journeys through the ocean, and not through the air.

The annual migration of the Monarch Danaid can be called the most colorful in the natural world. Among insects, only dragonflies surpass them in travel length, the duration of the monarch's migration is 7 thousand kilometers, it requires 3-4 generations, and as a result, these butterflies sometimes cross Atlantic Ocean. A very spectacular event.

Monarch populations can be found in Australia and New Zealand, where they are called nomad butterflies.

North American deer populations migrate the longest distance of any land mammal, traveling more than 5,000 kilometers annually. Herds of migratory animals can grow to impressive sizes - up to half a million individuals, rivaling in scale only the great African wildebeest migrations. Through the winter reindeer move to forested areas where it is easier to find food, and in summer they migrate to glacial areas.

Another of the most impressive natural migrations is salmon movements. This fish surprises with the ability to swim in both sea and fresh water during migration. Salmon are able to travel thousands of kilometers inland along rivers and water channels, after which they can even descend thousands of meters along mountain streams and return to the waters where they were born.

Zooplankton are the myriad of organisms that drift through the water column of the world's oceans and seas, including species such as jellyfish, krill, and fish fry. Zooplankton's migrations are different, moving up and down in the depths of the ocean rather than traversing the landscape (although they can do that!) Zooplankton's movements, known as "vertical migration", rival those of better-known nomadic species like reindeer or arctic terns.

Despite their tiny size, some zooplankton huddle into vertical shoals up to a kilometer in size almost every day in a constant search for food.

Although only a few types bats migrate, those few representatives that travel seasonally do it very spectacularly.

In fact, one of the largest mammalian migrations in the world is the annual journey of the Zambian straw-yellow fruit bats. During migration, an amazing blanket of 8 million bats covers the sky as these animals fly to feast on their favorite fruit delicacy.

The seasonal movement of red crabs across Australia's Christmas Island is an amazing sight. More than 120 million red crabs call this remote island their home, and every year they turn it into a huge moving carpet, moving en masse to the ocean to lay their eggs.

During periods of peak migration, it is often necessary to block roads on the island, as crabs completely cover the surface of the earth. Scientists recently discovered that hormonal changes are causing crabs to undertake this energetic journey.

Many species of sharks travel thousands of miles daily in open water, combing the ocean in search of food. White shark is a traveler for long distances, sometimes crossing during the year Indian Ocean between South Africa and Australia and back. Also migrate larger and more docile whale sharks, but the patterns of their movements are not very clear.

Tuna is among the fastest swimming migratory fish. At least one tuna has been recorded to have traveled 40,000 kilometers across the Pacific Ocean three times in 20 months between the US and Japan.

The amazing migration was documented by the census organization marine life, which includes experts from 73 countries.

pinnipeds, like seals, sea ​​lions and walruses are also known for their incredible sea travel. Fur seals are known to swim a quarter of the way around the world every year. It was recorded that sea ​​elephants migrate over 20,000 kilometers annually, they also dive deeper than other seals. The migratory path of walruses passes through the ice-covered Arctic waters, this journey was a mystery to scientists until recently.

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Genetic similarities between fossil snails found in Ireland and the Eastern Pyrenees have led scientists to speculate that humans migrated to Ireland from Europe around 8,000 years ago.

"Everything is like animals" came to Croatia to shoot several programs with the help of the Aqua Maris Institute and go back. Or maybe not leave, but on the contrary, stay and become a successful invasive species. Go bad! Simple Rules for those who come in large numbers - in our first practical issue.

Movie stars will soon be on the red carpet to win (or lose) the US Academy Film Awards. But why can only people become nominees? We have translated the Oscar categories into the highest achievement for furry animals, crawling insects and other organisms that live on our planet. Who will win the best costume award? And what about the best makeup? Read on to find out about the winning animal stars.

None of the Earth's land ecosystems plays such an important role as rain forests. From 50 to 75 percent of all species of the planet's fauna live in these territories, and millions more animals remain undiscovered. The amazing biodiversity in these habitats has made them home to some of nature's most interesting creatures.

• Dogs, as you know, understand everything - they just don't speak. Anyone who has ever looked into the eyes of a dog will no longer doubt this truth. But this is how they see it the world? How do we seem to them? In general - what are the true views of our smaller brothers?

Stanislav Drobyshevsky

Why did ancient people settle on the planet and how did they end up in its most remote points? The appearance of man in the tropics and the peculiarities of our physiology. Why did people go north? Desire to have something new living space with resources. The property of all living beings to occupy a free territory. Why did animals spread faster than Homo erectus? Natural limits of migration: oceans, mountain ranges and rivers. Settlement along convenient paths along sea ​​coasts. What are the most distant traces of the first hominids and sapiens known to scientists? The settlement of the whole planet by a reasonable person by the time about 10,000 years ago. Anthropologist Stanislav Drobyshevsky will tell us about this and much more.

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Stanislav Drobyshevsky

How did ancient people get to distant lands? Can a hunter-gatherer go anywhere on land? Seafaring. Three ways from Africa. Road to Indonesia. The distances that Homo erectus could cover on water and our understanding of their mental and physical abilities. Why do we underestimate the capabilities of our ancestors, Cro-Magnons, and parallel humanity - Neanderthals, Denisovans, Floresian people? What swimming facilities are capable of making modern primitive tribes? Coastal sailing and sailing in the open sea and ocean. Exchange of obsidian between the inhabitants of the islands of Melanesia separated by hundreds of kilometers. Road to Australia. Man's desire to explore new space. Anthropologist Stanislav Drobyshevsky will tell us about this.

Migration, (from Latin migrans) means resettlement. Migrations are widespread among animals of all the globe and are an interesting adaptation to the transfer adverse conditions that sometimes occur in nature.

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

Migrations of animals arise under different conditions and they pass differently.

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

In general, migrations in mammals are characteristic of a relatively smaller number of species than in birds and fish. They are most developed in marine 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 eviction. Periodic evictions - migrations include those that represent the mass departure of animals from breeding places without subsequent return to their former habitats. According to science, such evictions are caused by a sharp deterioration in 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. This shows that numerous circumstances can cause the movement of a mass of animals over long distances. Invasions - the movement of animals outside their homeland. Such movements differ from true migrations in their irregularity and long intervals between successive invasions. Sometimes they are considered as initial stages the formation of real migrations arising from explosive settlements - "emigrations". Invasion is like a safety valve triggered by excess population density. In itself, this favors the existence of the species only indirectly. In normal vivo population processes are in equilibrium, and population growth resulting in eviction rarely occurs. Invasion is a phenomenon, the disadvantages of which are striking, but which, at the same time, for a long time gives 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 inherent ordinary squirrels. They (migrations) arise quickly in response to unfavorable conditions. Migration begins in July-August, when the squirrels begin to feed on seeds and nuts of a fresh crop and discover their deficiency. Migration continues for about 6 months. Squirrels sometimes overcome up to 500 km or more. Proteins do not migrate in groups, but singly. Squirrel wanderings are periodically repeated every 4-5 years and greatly affect the yield of furs and the economy of squirrel hunters. The speed of squirrels during migration reaches 3-4 km/h.

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

Seasonal migrations are especially pronounced in places with a sharp change in habitat conditions from winter to summer, in places with severe winters and hot, dry summers. This phenomenon has the character of a purposeful mass movement, although it is not always clearly visible. The causes of seasonal migrations are always complex. However, the most tangible of them is hunger. Another reason is the attack on animals by gnats: mosquitoes, gadflies, horseflies.

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

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

Vertical migrations are understood as those when animals in the same season of the year find the best conditions for themselves in the spring in high-mountain regions in alpine meadows, and in autumn they descend to the foothill pastures. Such movements are typical for the inhabitants of the mountains - goats, chamois and other ungulates. Mountain ungulates by the summer rise to the upper mountain belts with their rich herbage, 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 places of daytime haulouts to places of watering places, salt licks and feeding. Daily migrations are characteristic of hares, deer and other animals.

All the aforementioned migrations are called active because the animals carry them out with great excitement, they sometimes appear in settlements and in other places that are not typical of 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 breeding places and habitual habitat with the help of ice or water currents. For example, migrations of walruses, polar bears, arctic foxes are known, caught on ice floes, which were carried away by the current into the ocean to some islands. Hares and muskrats during floods, falling on floating objects or ice floes, go downstream for long distances. Different modes of transport play a significant role in passive migration. Especially characteristic is the settlement through vehicles mouse rodents. As a result of passive migrations, house mice, rats and other animals were settled almost all over the world. Many of the introduced species of animals get along well in new places. Thus, there is an increase in the range of certain species of harmful rodents.

Rodent migrations are of interest in the sense that many of them can be used in hunting and trade and in the control of agricultural pests.

Graduation work

Performed by Viktor Tkachenko

Secondary school - Lyceum No. 265

St. Petersburg

I. Introduction

The entire animal world of the planet is in constant motion: from the smallest planktonic organism to giant whales in the seas and oceans, from tiny midges to huge albatrosses in the air, from such small mammals like lemmings, to elephants - everything moves, everything moves in the surrounding space, looking for the best habitats, rich in food or convenient for breeding. Some animals make their movements irregularly, others strictly cyclically: once a day, a month, a season, a year, or even once every few years. For some inhabitants of the planet, such a journey is the only one in life, while others undertake it many times. It is as if a gigantic pump, or rather a multitude of pumps, pumps the animal population of the planet, mixing it and directing it along one or another channel.

However, all this looks chaotic only at first glance. Animal movements are governed by complex laws closely related to changes in the environment. In fact, the movements themselves are the most important adaptations that expand the ecological capabilities of the species.

Animal movements are strictly limited in space and time. They follow certain rhythms. It would seem a contradiction: on the one hand, constant movement, on the other, binding to certain points in space, certain routes, territories that ensure the existence of each separate species, a separate population, a separate organism in infinitely diverse environmental conditions. Therefore, the movements of animals are so diverse and complex, so difficult to compare and classify. The classification of migrations is difficult not only because of their insufficient knowledge, but also because of the diversity of their manifestations in different groups of animals.

Every animal can face problems of food shortage, overpopulation, excess predators or habitat destruction, and often the best way out for him is to change his place of residence. The success of animals is largely determined by their mobility, and it is not surprising that, with a few exceptions, natural selection favored the evolution of mobile species.

II. Types of animal movement

There are three types of animal movements: minor movements, migrations and migrations.

Minor movements are characteristic mainly of lower animals, which lead mainly sedentary life, limited movement within a small area. An example is an ordinary saucer, which, at low tide, leaves its place on a rock in search of food, and when the tide approaches, it returns to its place again. Each saucer has its own place on the rock, which has a certain shape.

Migrations are a type of movement of animals caused by the need to get food. The nomadic way of life is typical for the inhabitants of arid and semi-arid regions. If the vegetation is too sparse for a population of animals to constantly feed in a given area, the inhabitants of these places are forced to make long transitions from one feeding area to another. So, moose gather together in winter and move to winter habitats and there, in this limited area, remain until spring. In the warm season, they lead a truly nomadic lifestyle, moving across the vast expanses of the country.

Migrations are regular and directed movements "to and fro". At the same time, in the behavior and lifestyle of animals there are characteristics. In a number of species, animals migrate several times in their lives, in others - only once (migrations will be discussed in more detail below).

There are no clear distinctions between periodic migrations, migrations and other movements. But all of them are part of the general complex of adaptive properties that ensure the distribution and survival of animals. Migration and nomadism of animals are different. Each species has its own characteristics. In some animals, migrations occur only during the period of family breakdown, when these animals are evicted from their birthplaces, and usually over short distances; for others, migrations are repeated annually in certain seasons of the year due to changes in environmental conditions, while for others, during the years of a sharp increase in the number of species, mass eviction of animals occurs without returning to their birthplaces, and, finally, for fourths, periodic migrations occur during the day, which is associated with their lifestyle and biological habituation. All this greatly complicates the study of migrations, which are of great interest to biological science.

III. Origin of migrations

AT in general terms science knows a lot, especially about the ways of animal migration. However, the causes of their occurrence and the orientation of animals during migration over long distances have not yet been sufficiently studied and are in given time the subject of research by scientists from many countries.

Migrations are characteristic of many mammals, but people know less about them than about bird flights and fish migration. Animals lead a more hidden lifestyle. Observations of them are possible only with special studies.

For centuries, most of the theories that explain migration were based on the most bizarre guesses, often completely wrong. The strange, regularly repeated movements of animals have been of interest to people since the time when ancient hunters first began to follow herds that migrated across vast savannahs. tropical Africa. On the rocks and walls of caves, such as Lasko, Altamira and Tassilin-Angier, masterpieces ancient painting preserved images of horses, bison and primitive bulls, which served our ancestors for thousands of years as a source of food and other livelihoods.

Even after the transition to agriculture, people were wondering why some fish, birds and animals are found only in certain seasons and mysteriously disappear at other times of the year, in order to reappear with the same inexplicable regularity after a few months.

In the 16th-18th centuries, a number of individuals believed that some animals, in order to avoid the adverse conditions of the coming cold weather, lay at the bottom of reservoirs and surfaced in the spring. Such a bizarre hypothesis was supported by the Archbishop of Uppsala from Sweden, Olaf Magnus, Dr. Samuel Jones (1709-1784), the creator of the modern system of plants and animals, Carl Linnaeus (1707-1778), naturalist Lazzaro Spallanzani (1729-1799) and many others. Aristotle (384-322 BC) put forward a fantastic hypothesis of "transmutations", which explains the seasonal disappearance of some animal species and the simultaneous appearance of others. He even stated that animals were seen directly at the moment of transformation. This myth has survived to this day in some remote rural areas of England. But later, towards the end of the 18th century, the theories became more real, closer to true migrations. The vast majority of biologists, especially in the last century, when "explaining" seasonal transitions, referred to "innate instinct", "generic habit", usually without even putting any specific content into these concepts. Only later, with the development of IP Pavlov's teachings on conditioned and unconditioned reflexes, did they begin to attempt to formulate the concept of instinct more specifically, in a physiological sense. And finally to late XIX century, the migration theory was recognized as proven.

The main reason for migration is the need for food and conditions for reproduction, as well as competition for convenient habitats. When, for example, a herd of buffalo or wildebeest doubles in size, its members are forced to roam in search of food over much wider areas than before. Because they serve as food fresh grass, the abundant growth of which is associated with a certain season, the movements of these animals also become seasonal. Before the colonization of North America, bison made such trips twice a year, going from Canada to Mexico.

Much less often, migration is driven by the desire to protect oneself from climatic extremes. Even in the islands of the North Arctic Ocean neither musk oxen nor bull-hunting wolves try to move into more warm places. Arctic foxes even move further north at this time of the year to stay close to polar bears and feed on the remains of the seals they have killed. Lemmings and Scottish hare hares also remain to winter in the north, and besides them, other animals and birds. Even the baribal bear does not go south, except perhaps in the most harsh winters when he moves to places where you can safely hibernate without being subjected to such ordeal(if energy resources are overused, he runs the risk of not waking up after hibernation).

Migrations arose in animals in the course of their historical development; they are an interesting biological adaptation. The emergence of migrations is, of course, associated with the evolution of the species to which they are characteristic. They have evolved from the aggregates of animal movements over countless generations. Animals that went in the wrong direction died. Those that chose the right path survived and returned with offspring. At first, there was no need to travel long distances, it was enough just to find an unoccupied territory; but, repeating every year, wandering acquired the character of a stable habit, which eventually grew into an instinct characteristic of the entire population.

Migration ecology arose and is developing as a synthesis of ecology and physiology. This field of study of migration covers a wide range of different aspects migratory behavior. It is very interesting to study the issues of the variability of migratory behavior, the difference in the timing and routes of migration, the individual variability of the migration distribution in time and across the territory in different species.

Do you know why animals migrate? Grade 7 learns about this in biology lessons. And even then, during the acquaintance with the secrets of biological science, the minds of children begin to be accustomed to understanding the everyday fact: people migrate, animals migrate. And if you understand well, the reasons are the same for everyone.

Animal migration (lat. migratio) is the regular movement of a group of animals with a change in the main habitat along a certain route. Such phenomena are most common in birds (we all observe the migration of storks, geese, ducks, starlings and other birds in autumn) and fish. Movements of animals have been studied less. This is due to the fact that they lead a mostly secretive lifestyle, it is often impossible to track them.

Migrations have a pronounced adaptive character; this feature of representatives of the animal world is observed in the most different types and arose in the process of evolution.

Seasonal migrations are more characteristic of birds, inhabitants temperate latitudes. They are also inherent in some mammals: wildebeest, reindeer, some varieties of bats, fish (sturgeon, European eel), reptiles (sea turtle), crustaceans (lobster), insects (monarch butterfly) change their habitat.

Why do animals migrate?

The most main reason animal movements - a change in living conditions, most often in the worst side. For example, they move from the tundra to the forest-tundra with the onset of winter due to the lack of food and the difficulty of obtaining it in areas covered with snow. And seasonal migrations of microscopic animals to shallow waters from the deep parts of lakes are associated with changes in water temperature.

An equally important motivation is reproduction, when an animal needs a different Environment for procreation. Another reason for migration is related to natural disasters. We will try to consider each of the reasons in this article with an example.

Types of animal migration

Conventionally, two types of migration can be distinguished - active and passive. In the active migration of animals, several subspecies are distinguished: movements are seasonal (daily), periodic (horizontal and vertical), and age. Let's try to figure out what each variety is.

So, seasonal (daily) migration of animals. Examples of such movements are best seen in fish and birds. To date, about 8,500 species of birds are known to science, most of which are sedentary, although they are subject to migration within their habitat for the duration of nesting. Seasonal movements of birds for wintering are more characteristic of the inhabitants of the Arctic and temperate latitudes: with the approach of the winter period, birds fly to a milder, warmer climate.

Interesting fact: what more bird, the longer distances it travels, while the smallest migrating birds can stay in the air continuously for up to 90 hours, covering a route up to 4000 km.

Fish migrate vertically: during rain they are practically on the surface, in heat or winter they tend to the depths of water bodies. But only two fish change their habitual habitat - salmon and European eel. Surprisingly, but true: the change of reservoirs with salt and fresh water occurs in these fish twice in their lives - at the time of birth and during the breeding season, however, this applies only to females, which die after laying eggs.

Interestingly, at the time of salmon spawning, brown bears also migrate, leaving the forests, settling on rivers teeming with salmon. Thus, it turns out that they follow their food supply.

As noted earlier, periodic animal migrations can be divided into two subspecies: horizontal and vertical. Let's consider these phenomena in more detail.

Horizontal migrations of animals are associated with the movement of individuals in search of food. So, for example, by summer, a gray whale moves from the North Ocean to the Atlantic (subtropical, tropical part), where at this time it is full of plankton - the whale's main food.

Vertical migrations are inherent in alpine animals, which, in winter period descend into the forest belt, and in the summer, as the snow melts and the grasses burn out in the lowland, they rise back to the mountain.

There is also such a thing as age-related migration of animals. Such movements are better revealed by the example large predators. So, the tiger, in essence, is a solitary animal with its own huge territory, which it leaves only during the rutting season. The cubs born into the world live with the female until they reach sexual maturity (usually 3-4 years), after which the males separate and leave the family in search of their own territory.

Reasons and examples of migration

We have already talked about what such a phenomenon as animal migration is connected with. Examples on specific representatives will be considered below.

Let's start with fish, since only two of their species are subject to movement. These include salmon and European eel. There are other few species of animals that migrate, but we will talk about them later. So why do fish migrate? What causes it?

Change of fish habitat

Anadromous fish - a species that lives in a specific habitat, but drastically changes it during the breeding season. What is it connected with?

Salmon (lat. Salmo salar) is born in fresh water, then with river flows quickly moves to the sea-ocean, where it lives for 5-7 years in anticipation of puberty. And now the long-awaited moment has come - the individuals have grown and are ready to leave offspring. Only here's the problem - salty water they like it, but the kids refuse to be born in it. The fish “remembers” that it was born in fresh water, which means that it needs to change the salty seas-oceans to rivers, and even better, to mountain ones. There are the most favorable conditions for reproduction. Only not all parents will achieve the desired goal - a predator sits here, which deftly catches a fish from a mountain stream, ripping open its belly and eating only caviar. Only capable of this Brown bear, which is tied to the migration of animals - the source of food supply.

European eel (lat. Anguilla anguilla) - complete opposite salmon. The eel is born in salt water, this happens at a depth of up to 400 m. The female produces about half a million eggs, which turn into a larva that looks like a willow leaf. For their fundamental difference from their parents, the larvae received a separate name - leptocephalus. On the example of these fish, we can consider in detail the type of passive migration: the larvae float to the surface, they are picked up by the Gulf Stream, and so for three years they move in warm water to the coast of the European part of Eurasia. By this time, the leptocephalus takes on the shape of an eel, only reduced - about 6 cm. At this moment, the eel moves to the mouths of the rivers, rising upstream, the fish turns into an adult. So 9 or maybe 12 years pass (no more), acne becomes sexually mature, sexual differences in color appear sharply. It's time to spawn - back to the ocean.

Mammal migrations

(from lat. Eschrichtius robustus) lives in the Arctic Ocean, but, paradoxically, females and males from October begin to move south along the coast. By December-January, pairs reach the Gulf of California, where in warm waters they start mating and giving birth, after which the males return to the north, and pregnant females and individuals with cubs return home only in March-April.

Pregnancy in whales lasts about a year, so in warm waters they either conceive or bring new offspring into the world. For young animals, this is very important - in the first 2-3 weeks of life, babies in warm waters gain fat layer, which allows them to return to the harsh Arctic Ocean.

Using the example of moose, we can explain such a concept as the migration routes of animals. Elk, in the common people "elk" (from lat. Alces alces), is common in the forest zone of the Northern Hemisphere. As soon as the first snow appears, the rivers are covered with ice, the elk begins to move to the southern regions, where grass growth is preserved, and water bodies do not freeze. It is interesting that, migrating from October to January, moose follow a trodden path: females with young animals follow first, followed by males. On the way back, the animals return by the same road, only now the males go ahead, clearing the path from overgrown greenery. As they approach the habitat, the groups disperse - single females in one direction, females with cubs in the other, and males in the third.

Tigers (lat. Panthera tigris), the largest representatives of cats, lead a solitary lifestyle: a female requires up to 50 km² of personal territory, for a male - up to 100 km². The meeting takes place during the breeding season, most often the female herself attracts the male, leaving various marks. Having fertilized the tigress, the male returns to his territory or in search of the next female.

Here we see an example of animal migration within the habitat, but with violation of territorial boundaries. The new offspring lives with their mother until the "kids" learn to hunt, which takes quite a long time. So, the cubs are with the tigress until puberty, after which the already grown individuals go to conquer new territories. The previously described European eel can be added to examples of age migration.

Mass migrations of animals are inherent in many species, but the movement of bats is an indescribable sight. In general, bats are prone to but if the animals live in the temperate zone, then they are forced to go south for wintering. If the air temperature in winter is kept within 0 ºС, then bats can overwinter in the attics of buildings. At this time, mice fall into winter sleep. During forced migration, bats are guided by instincts and move along those routes that are used from generation to generation.

Let's think about vertical migration and pay attention to the inhabitants of the mountains. In the mountains, at an altitude of thousands of meters, an extraordinary zoodiversity: chinchillas, Snow leopards, pumas, goats, rams, yaks, juniper grosbeak, white eared pheasant, kea. All inhabitants of the highlands are characterized by thick wool and plumage, which prevent hypothermia of animals. Some animals hibernate in burrows in winter, and birds make nests in rock crevices and bask in groups. But representatives of ungulates descend to the foot of the rocks in search of food, followed by predators chasing their prey.

Interesting fact: mountain goats and rams are able to migrate over the rocks without stepping onto mountain paths. And all thanks to the special structure of the hooves: soft pads are quickly restored, the hooves have the ability to move apart widely, which is important when moving on rocky terrain.

Reasons for changing bird habitats

Migratory birds are observed in both the Northern and Southern Hemispheres. The sharper the climate changes, the more pronounced the flights. So, the crows and turtledoves familiar to us become migratory if they live in the northern regions, where severe, snowy winters deprive birds of the opportunity to obtain food. The inhabitants of the southern part of Europe lead a sedentary lifestyle due to the absence of sudden changes in temperature. The behavior of birds in Africa is interesting: here one can simultaneously observe movements both from north to south and from south to north. The reason for such migrations is hidden in the preference for a humid or arid climate.

Birds can make quite long flights. For example, the habitat (lat. Ciconia ciconia) is in Europe, and the bird winters in Africa, covering a distance of 10-15 thousand km 2 times a year. But the most unique among migratory birds is the arctic tern (lat. Sterna paradisaea). The tern nests in the tundra and breeds chicks here. With the onset of autumn, it migrates to Southern Hemisphere and returns in the spring. So, twice a year this bird travels up to 17 thousand km. It is interesting that in spring and autumn the tern flies by different routes.

Movement of reptiles

Let's look at the example of a sea turtle (lat. Cheloniidae), what is the reason for the mass migrations of animals. Sea turtles only breed in certain places. Thus, the Atlantic Ridley (lat. Lepidochelys kempii) breeds on a single island in Mexico, where in 1947 scientists recorded approximately 42,000 females that sailed to lay eggs.

Thanks to the olive sea turtle (lat. Lepidochelys olivacea), the term "arribida" appeared in science. The phenomenon is that thousands of olive ridleys gather for mating in one day, after which, having chosen an island, the females lay millions of eggs almost simultaneously.

Why do crustaceans migrate

Lobster (lat. Achelata) also moves at a certain time. Science still does not explain the reasons for the migration of animals of this species. In autumn, lobsters gather in a column of thousands of individuals and make a forced march from Bimini Island to the Grand Bahama Bank. So far, there is only one hypothetical explanation for this behavior: in the fall, daylight hours begin to decrease, which forces the spiny lobsters to change their habitat.

Spiny lobster (lat. Panulirus argus) is also considered a nomadic representative of crustaceans. At the beginning of winter, it moves to deeper waters. Scientists long time it was believed that the reason for the movement of the lobster was reproduction, but it was later found out that egg laying occurs much later than migration, only after a few months. Scientists name different reasons for changing the habitat of spiny lobsters. Some, for example, believe that the migration of these crustaceans is a relic ice age when in winter they changed cold waters to warmer deep ones.

Migration of lobsters is a truly amazing sight! Several hundred individuals move in columns one after another. What is most interesting, lobsters maintain constant contact with each other. So, the one who is behind keeps his antennae on the shell of the one who goes in front.

Examples of insect migrations

(lat. Danaus plexippus) is the most famous inhabitant of North America. During periods of animal migration, it is noticed on the territory of Ukraine, Russia, the Azores, North Africa. In Mexico, the state of Michoacán, there is even a monarch butterfly sanctuary.

In the issue of migration, this insect also distinguished itself: the danaid is one of the few representatives of its class that can cross the Atlantic Ocean. Already in August, the monarchs begin to migrate to the southern territories. The life span of this butterfly is about two months, so the migration of animals occurs in generations.

Diabase - the reproductive phase, which enters the danaid, born at the end of summer, which allows the butterfly to live for about 7 more months and reach the wintering place. The monarch butterfly has an amazing "solar sensor" that allows the third and fourth generations to return to the wintering places of their ancestors. Interestingly, the most favorable climate for these butterflies turned out to be in Bermuda, where some insects remain all year round.

European species also migrate. Thistles, for example, winter and breed in North Africa, and already their offspring move to the north and hatch the summer generation there, after which they fly back to Africa. In the spring, history repeats itself.

Interestingly, burdocks fly in groups and can cover a distance of 500 km in one day. In total, during the migration they can fly as much as 5000 km! And their flight speed is rather big - it is 25-30 km / h.

Some butterflies do not migrate constantly, but only depending on conditions. These include urticaria, swallowtail, mourning, cabbage, admiral. All these species are found in Northern and Central Europe, but may move south under adverse circumstances.

But for example, it annually moves from Turkey and North Africa to East and Central Europe. There these butterflies breed, but, unfortunately, in winter most of their offspring dies. In spring, the next generation migrates from the south.

A small conclusion and conclusions

So we figured out a little about why animals migrate. Indeed, the reasons are varied, but I want to note the two most common. We all remember the story of Mowgli, especially the moment when a period of drought began in the jungle. All the animals reached for the only river where parity was to be observed: everyone is equal, hunting is taboo. Such migration occurs, as a rule, within the habitat, when animals (more often inhabitants of the steppes, semi-deserts, deserts) migrate in search of food and water from place to place during the drought, most often they are representatives of ungulates. However, the movement of herds, herds also entails the movement of some predators (hyenas, vultures), which need to be close to the food base. So food and water make you migrate large groups several kinds of animals.

An important reason is reproduction. The active migration of animals during the breeding season, in particular, sea turtles, is impressive and fascinating.

Many species of animals move: some within their habitat, others travel thousands of kilometers to reach a favorable climate; still others radically change their habitat (remember the sturgeon and the European eel).

Yes, the migrations of different animals have a different character, different reasons, but they all have one thing in common - the thirst for life.

Material from the Uncyclopedia

Scientists call animals moving over long distances migrations. Travel all insects, fish, reptiles, amphibians, mammals, birds. Migrations are periodic - regular - and non-periodic.

Regular travel of animals is usually associated with seasonal changes in nature. The onset of cold weather in countries with a temperate or cold climate or heat, followed by droughts in the steppes, deserts and semi-deserts, deprive many animals of food, and they move to places where food is available at that moment. The life of some animals is associated with the harvest of certain feeds, such as seeds coniferous trees. In years with a poor harvest of squirrel seeds, the nutcracker, crossbill, sable, marten, bear leave their inhabited places and move to other areas. These are irregular migrations.

There are also catastrophic migrations, when habitat conditions change dramatically. broken, for example, old house, and everyone who lived in it - birds, mice, insects - go in search of a new haven.

Sometimes migrations take a very long time. Fry salmon fish, leaving the eggs, grow up a little and go down the rivers to the sea, and from there to the ocean. It will be several years before they return to their native lands to spawn. In some northern gulls, chicks, until they become finally adults, capable of breeding their own offspring, roam the southern countries for several years.

Famous for their migrations river eels. On spawning from the rivers of the basin Baltic Sea eel goes to the shores of America, to the Sargasso Sea. The hatched larvae, gradually growing up, make their way back. If you measure it in a straight line, then it will be 8 thousand km.

Some birds cover even greater distances during migrations. Arctic terns from the shores of the Arctic Ocean fly over 17 thousand km to Antarctica. Even our common starling, ringed on the Curonian Spit, managed to fly to Belgium in a day, 1230 km away. Fans of such long journeys are among the insects. Once in Africa, butterfly migrations were observed that lasted 4 months. Dragonflies, butterflies and ladybugs fly over mountain ranges, oceans, suddenly appear in huge flocks in the most unexpected places.

The speed of movement of animals during migrations is amazing. A ruby ​​hummingbird weighing only 3.5 g flies over 900 km in 25 hours Gulf of Mexico, making 50 wing beats per second. Some birds make their non-stop flights for 105-115 hours. Fat reserves in the body, which have a very high calorie content, serve as a kind of "fuel".

Some species prefer to travel during the day, others at night, and some both during the day and at night.

What draws them to distant and dangerous wanderings? There are various assumptions. The most common of these is the desire to avoid adverse conditions: cold, heat, drought and associated famine.

Mass movements of animals, probably, took place over many geological epochs, gradually becoming fixed in their "memory" from generation to generation. It could have been different. Once, many millennia ago, the climate of our planet was different, the ancestors of modern animals lived in southern countries, and the descendants annually return to their native places. True, observations have shown that the changes introduced by man into nature: the creation of new reservoirs, the reduction of forests, etc., affect the migrations of animals. The old ones disappear, new ways, places of stops, winterings, habitats appear.

How do animals navigate, unmistakably find their way?

Not all the sense organs of animals and their capabilities are known to people yet. Animals are able to navigate by the sun, stars, having a "compass" unknown to us. An internal, highly accurate biological clock allows them to correct for the "compass". Animals catch and use favorable winds, currents, magnetic and gravitational fields of the Earth, are able to feel the slightest changes. barometric pressure. They keep in mind detailed map terrain and the most noticeable objects on it. Many people use their sense of smell to find their way. Pigeons perceive polarized and ultraviolet radiation, hear infrasonic noises at ultra-low frequencies of long waves. Bats use echolocation. Locators are used by many aquatic animals - whales, fish. The locator successfully replaces the organ of vision with them. Wasps, honey bees memorize voluminous objects well, pointing them in the direction. Fish have a very sensitive sense of smell. For most of them, it serves as the main pointer for migrations. This is how salmon and other migratory and semi-migratory fish find their way to their native rivers.

You can also conduct various experiments in your circle and at the biostation for the study of animal migrations, take part in the work of scientists, completing their task. The one who will be able to unravel the secrets of animal migrations, their "navigation instruments", will make one of the largest scientific discoveries.