Do you know why the migration of animals?7 class learns about it in biology class.And even then, while exploring the mysteries of biological science, consciousness is beginning to teach children to understand the everyday fact: people migrate, migrating animals.And if it is good to understand the reasons for all the same.
migration of animals (lat. Migratio) - regular movement of a group of animals with the change of the main habitat for a particular route.The most common birds such phenomena (we are all witnessing the fall migration of storks, geese, ducks, starlings and other birds) and fish.Movements of animals studied less.This is due to the fact that they are mostly secretive way of life, to follow them is often impossible.
Migrations have a pronounced adaptive nature, this feature of the animal world is seen in a variety of species and emerged in the course of evolution.
Seasonal migrations are characterized more for the birds, inhabitants of the middle latitudes.They are also characterized by some mammals: changing habitat wildebeest, caribou, some species of bats, fish (sturgeons, European eel), reptiles (sea turtle), crustaceans (lobster), insects (monarch butterfly).
Why do animals make migration?
biggest reason the movement of animals - changing environmental conditions, often for the worse.For example, the reindeer are moved to the onset of winter in the forest of tundra due to lack of food and the difficulty of its production in the area covered with snow.A seasonal migration of microscopic animals in the shallow water of the deep parts of the lake are associated with changes in water temperature.
no less important motivation - the multiplication when the animals need a different environment for the procreation.Another reason is related to the migration of natural disasters.Each of the reasons we will see in this article as an example.
Types of animal migration
are roughly two types of migration - active and passive.In the active migration of animals secrete several subspecies: there are seasonal movements (daily), regular (horizontal and vertical), age.Try to understand what constitutes each species.
So season (daily) the migration of animals.Examples of such movements are best seen in fish and birds.Today, science knows about 8,500 species of birds, most of whom are sedentary, although prone to migration within the habitat at the time of breeding.Seasonal movements of birds wintering greater inherent inhabitants of the Arctic and temperate latitudes: with the approach of winter birds fly in a softer, warmer climate.
Interesting fact: the more the bird, the longer distances it moves, with the smallest of migratory birds in the air may be continuously up to 90 hours, breaking the route up to 4000 km.
Fish also migrate vertically: when it rains are virtually on the surface, in summer or winter - tend to water depth.But only two fish change their familiar surroundings - a salmon and European eel.Strange but true: change of ponds with salt and fresh water occurs in these fish twice in my life - at birth and during the breeding season, however, this applies only to females who die after laying eggs.
interesting that at the time of spawning salmon brown bears, too, migrate, leaving the forest, settling in rivers teeming with salmon.Thus, it turns out that they follow their food supply.
As noted earlier, the periodic migration of animals can be divided into two subspecies: the horizontal and vertical.Consider these phenomena in detail.
Horizontal migration of animals associated with the movement of animals in search of food.For example, the gray whale to fly moves from the North Atlantic Ocean (subtropical, tropical part), which at this time is full of plankton - the main food of the whale.
vertical migration inherent in alpine animals that come down in the winter in the forest, and in the summer, as the convergence of snow and burning grass in the valley, climb back up the mountain.
There is such a thing as age migration of animals.Such movements are revealed best by the example of large carnivores.So, Tiger, in essence, a solitary animal with its own huge territory, which he leaves only during the rut.Was born cubs live with the female until the age of sexual maturity (typically 3-4 years), after which the males are separated and leave the family in search of their own territory.
reasons and examples migration
We already talked about what has caused the phenomenon of animal migration.Examples of specific representatives to consider further.
To begin acquaintance with the fish, as only two of their kind are subject to movement.These include salmon and European eel.There are a few other animal species migrates, but about them later.So why fish migrate?What is the reason?
Changing fish habitat
Anadromous fish - a species that lives in a particular environment, but at the time of reproduction it changes dramatically.What is the reason?
Salmon (lat. Salmo salar) are born in fresh water, then with a fast moving river flows into the sea, the ocean, where he lives 5-7 years in anticipation of puberty.And then came the long-awaited moment - individuals have grown up and ready to leave offspring.Just the thing - they like the salt water, but the kids refuse to appear in her light.Fish "remembers" that was born in fresh water, which means that it is necessary to replace the salty seas and oceans to the rivers, and even better - the mountain.There are very favorable conditions for reproduction.Do not all parents reach the desired goal - a predator sitting here, who deftly catches of fish a mountain stream, ripping bellies and eating away only spawn.Capable of such a brown bear, which is tied to the migration of animals - the source of fodder.
European eel (lat. Anguilla anguilla) - the exact opposite of salmon.Acne comes in the salt water of the Sargasso Sea, it happens to a depth of 400 m. The female gives birth to about half a million eggs, which become larvae, like a willow leaf.Larvae for its radical difference from their parents received a separate name - Leptocephalus.For example, these fish, we can consider in detail the kind of passive migration of the larvae float to the surface, their picks for the Gulf Stream, and three years since they moved in warm some water to the coast of the European part of Eurasia.By this time Leptocephalus taking shape eel, only reduced - about 6 cm. At this point, the eel moved to the mouth of the river, the river rising up, the fish turns into an adult.So runs 9, maybe 12 years old (not more), eels become sexually mature, sharply there sex differences in color.It's time to spawn - back into the ocean.
Gray Whale (from the Latin. Eschrichtius robustus) lives in the Arctic Ocean, but, paradoxically, females and males from October begin to move south along the coast.By December-January, the pair reached the Gulf of California, where the warm waters to mate and begin leave, then the males returned to the north, and pregnant females with cubs and birds are returning home in March-April.
whales Pregnancy lasts for about a year, so in the warm waters or conceive, or brings to light new offspring.For the young it is very important - in the first 2-3 weeks of life, babies in the warm waters of gaining body fat, which allows them to return to the harsh Arctic Ocean.
For example, moose can we explain such a thing as migration routes of animals.Elk in common, "elk" (from the Latin. Alces alces), is common in the forest zone of the Northern Hemisphere.As soon as the first snow, the rivers are covered with ice, elk begins moving to the southern regions, where growth is maintained grass, water does not freeze.Interestingly, migrating from October to January, moose are on the trodden path: the first traces of females with young, moving them males.On the way back, the animals are returned by the same route, but now males are ahead, clearing a path from the sprawling greens.With the approach to habitat disperse groups - lone female on one side, females with calves - to another, the males - in the third.
Tigers (lat. Panthera tigris), the largest feline, lead single lifestyle for the female takes up to 50 km² of personal territory for males - up to 100 square kilometers.The meeting takes place during the breeding season, most of the male attracts the female herself, leaving a variety of labels.Fertilize tiger, the male returns to its territory, or in search of the next female.
Here we see an example of migration of animals within their habitat, but a violation of territorial borders.New offspring lives with his mother up until the "kids" do not learn to hunt, which takes quite a long time.So Young are a tigress until puberty, after which it is grown specimens are to conquer new territory.Examples of age-migration can also add the previously described European eel.
mass migration of animals common to many species, but the movement of bats - the indescribable spectacle.Actually bats are prone to a sedentary lifestyle, but if the animals live in the temperate zone, you have to go for the winter in the south.If the air temperature in the winter is kept between 0 ° C, the bats can hibernate in the attics of buildings.At this time, the mouse fall into winter sleep.When the forced migration of bats are guided by instincts and move on those routes that are used from generation to generation.
Recall the vertical migration and draw attention to the inhabitants of the mountains.In the mountains, at an altitude of thousands of meters, unusual zooraznoobrazie: chinchilla, snow leopards, cougars, goats, sheep, yaks, juniper grosbeak, white-eared pheasant, Kea.For all the inhabitants of the highlands are characterized by thick fur and feathers to prevent hypothermia animals.Some of the animals in the winter to hibernate holes, and the birds in the crevices of the rocks and make nests basking groups.But representatives of hoofed down to the foot of the cliffs in search of food, behind them are predators, chasing their prey.
Interesting fact: mountain goats and sheep are able to migrate through the rocks, without stepping on the mountain trails.And all thanks to the special structure of the hoof: soft pads are quickly restored, hooves have the ability to widely move apart, which is important when you walk on rocky terrain.
reasons for changing bird habitats
Migratory birds are observed in both the northern and southern hemisphere.The sharper the climate is changing, the more pronounced flights.So familiar to us crows and turtledoves are migratory, if live in the northern regions, where the harsh, snowy winters deprived of the possibility of birds foraging.The inhabitants of southern Europe are sedentary because of lack of sudden changes in temperature.The behavior of birds in Africa here at the same time can be seen as a move from north to south and from south to north.The reason for such migration is hidden in the preference of wet or dry climate.
Birds can make a pretty long flight.For example, the habitat of the white stork (lat. Ciconia ciconia) - in Europe and wintering birds in Africa, 2 times a year to overcome the distance of 10-15 thousand. Km.But the most unique among the migratory birds - Arctic Tern (lat. Sterna paradisaea).Tern nests in the tundra, here displays the chicks.With the onset of autumn, it migrates to the southern hemisphere and spring returned.So, twice a year the bird overcomes 17 thousand. Km.Interestingly, in spring and autumn tern flying different routes.
Let us consider the example of sea turtle (Lat. Cheloniidae), what is the cause of mass migrations of animals.Sea turtles reproduce only in certain places.For example, Atlantic Ridley (lat. Lepidochelys kempii) replicates on a single island in Mexico, where in 1947 researchers were registered about 42 thousand. Females who sailed to lay eggs.
Thanks olive sea turtle (Lat. Lepidochelys olivacea) in science the term 'arribida. "The phenomenon is that thousands of olive Ridley one day going to mate, then selecting Island females almost simultaneously make masonry million eggs.
Why migrate crustaceans
Lobster (lat. Achelata) also moves at a certain time.The reasons for the migration of animals of this species still does not explain the science.In the fall of lobsters collected in a convoy of thousands of individuals and make the march of the island of Bimini to Grand Bahama Bank.While there is only one explanation for such conduct alleged: autumn daylight begins to decline, which makes changing lobster habitat.Spiny lobster
(lat. Panulirus argus) is also considered a representative of the nomadic crustaceans.At the beginning of winter, he goes into the deeper water.Scientists have long believed that the reason for moving the lobster - reproduction, but later it was found that egg-laying occurs much later migration, only a few months.Scientists call the various reasons for the change of habitat crayfish.Some, for example, believe that migration of these crustaceans - a relic of the Ice Age, when they have a cold winter in the warmer water depth.
migration of lobsters - a truly amazing sight!Several hundred individuals moving columns each other.What is most interesting, lobsters remain in constant contact with each other.So, whoever is behind, holding its antenna on the shell of the one who goes ahead.
Examples of insect migration
monarch butterfly Monarch (lat. Danaus plexippus) - the most famous inhabitant of North America.In periods of animal migration of its notice on the territory of Ukraine, Russia, the Azores and North Africa.In Mexico, the state of Michoacan, even a monarch butterfly reserve.
On the issue of migration is also an insect difference: the monarch - one of the few representatives of its class, capable of crossing the Atlantic Ocean.Already in August, the monarchs begin migrating to the southern territory.The life expectancy of this butterfly - about two months, so the migration of animals takes generations.
Diabase - reproduction phase, which comes monarch, born in the late summer, allowing the butterfly to live for about 7 months and reach the wintering grounds.Monarch butterfly has a wonderful "solar probe", which allows a third, a fourth-generation return to the wintering grounds of their ancestors.Interestingly, the most favorable climate for these butterflies appeared in Bermuda, where some insects are all year round.
migratory and European species.Painted Lady, for example, winter and breed in North Africa and their descendants have moved to the north and there are prints of the summer generation, and then flies back to Africa.In the spring of history repeating itself.
Interestingly, fly Painted Lady groups and may one day cover the distance of 500 km.Altogether during the migration as much as they can fly 5000 km!And speed they rather big - it is 25-30 km / h.
Some butterflies migrate constantly, but only depending on the conditions.These include hives, swallowtail, NYMPHALIS ANTIOPA, cabbage, Admiral.All of these species are found in North and Central Europe, but can be moved to the south under adverse circumstances.
But oleander hawk moth, for example, annually makes moving from Turkey and North Africa Eastern and Central Europe.There are these butterflies breed, but unfortunately, in the winter most of their offspring dies.In the spring migrating from the south the next generation.
small Summary and Conclusions
So we figured out a little bit and that is why animals make migration.Indeed, the reasons are varied, but would like to mention two of the most common.We all remember the story of Mowgli, especially the moment when in the jungle came the period of drought.All the animals were drawn to the only rivulet, where he was to be observed parity: all are equal, hunting - a taboo.