Why animals living further south have ears. Geographical laws and some environmental factors
"The protruding parts of the bodies of warm-blooded animals (ears, legs, tails) are smaller in cold climates than in warm ones."
Explanation: the larger the ears and tails, the larger the surface of the body through which heat escapes. For northern animals, this is not beneficial, so their ears and tails are small. For southern relatives, on the contrary, it is convenient to have a large surface in order to somehow cool.
Explanation: when an organism increases in size, its volume grows and its surface grows - everyone grows, but at different speeds. The surface lags behind - grows slower than volume, therefore, in large northern animals, the surface is relatively small. They all need this for the same - to give off less heat.
Example: the polar wolf is the largest of all wolves, the polar bear is of all bears, the wolverine is of all mustelids, the elk is of all deer, the capercaillie is of all grouse.
And why do such big animals as elephant and hippopotamus live in the south?
Because there is enough vegetation for them to feed themselves. - But at the same time they very hot. The hippo constantly sits in the water, the elephant is cooled with the help of its huge ears. (Mammoths living in temperate climates were the same size as modern elephants, but they had normal size ears and hair, as it should be for mammals.)
pinnipeds- very special and interesting animals that can live both on land and in water. Their paws have turned into flippers, so these marine animals are called pinnipeds. They eat fish, squid and crustaceans.
How are fur seals different from seals?
Fur seals and seals are close relatives and very similar. But seals have ears, but seals don't. In addition, fur seals very deftly jump on their flippers, and seals crawl on their stomachs.
seals
Seals (Odobenidae)- wonderful hunters. They have well-developed eyesight, because most of the time they are under water, where the lighting is very poor. These animals are able to find food even in the dark. The body of pinnipeds, with the exception of the head, is covered with a layer of fat 10 cm thick, and in some - even more. In pinnipeds - the fattest milk among all mammals. Seals do not chew fish at all, but swallow it whole. If the fish is very large, then pinnipeds tear it into pieces. Seals withstand temperatures down to -80C°.
Why do seals need flippers?
If there are fleas on the skin, the fur seal itches with its back flippers, and the seal with its front flippers. In the water, the fur seal paddles mainly with its front flippers, while the common seal uses its back flippers.
sea hare
photo: Mar Hoskuldsson’s
The bearded seal (Erignathus barbatus) is the most baleen among pinnipeds. His mustache is thick and curly. But in the water, they become straight and very long and help the seal find food on the seabed.
sea elephants
photo Jim Frazee
Elephant seals (Mirounga)− giants from the seal family. Their length is about 6 m, and their weight is more than 3 tons. These animals were named so not only because of their size, but also because of the nose, similar to a trunk, which hangs at the end of the muzzle of elephant seals. Elephant seals use their long trunk, up to 80 cm long, as a means of intimidation. In time of danger, the male raises his trunk up and his menacing roar spreads over the sea. The sea giant is very clumsy on land, but it swims well and dives deep. He is able to dive for food to a depth of 1400 meters.
harp seal
photo Steve Arena
The claws of the harp seal (Pagophilus groenlandicus) are a reliable defense against enemies. They are very sharp. The wounds that this animal inflicts do not heal for a long time.
Walrus
photo Allan Hopkins
Walruses (Odobenus rosmarus) found in the Arctic regions of the world. Today there are three subspecies. pacific walruses(Odobenus roasmarus divergens) live mainly in the Bering Sea. During the warm summer months, they can travel as far as the Beaufort Sea and the East Siberian Sea. Atlantic walruses(Odobenus rosmarus rosmarus) are found in the eastern and western Atlantic Ocean. Laptev walruses(Odobenus rosmarus laptev) are found in the Laptev Sea. Walruses inhabit areas of the Arctic that are mostly made up of ice. Walruses prefer shallow water areas so they can easily access food. This slow-moving marine mammal spends most of its time in or around water.
The walrus is one of the largest pinnipeds. This animal is known for its massive tusks, which are actually just enlarged teeth. These fangs can cut through 20 cm of ice. They can grow up to 90 cm, but the average size is about 50 cm. Males are larger than females, weighing up to 1200-1500 kg, and females from 600 to 850 kg.
Sea leopard
photo V Maxi Rocchi
Sea leopard (Hydrurga leptonyx)- the most bloodthirsty predator among pinnipeds has a reputation as the most fierce and formidable seal, as it feeds not only on big fish and penguins, but also attacks other seals.
hooded seal
Male hooded seal (Cystophora cristata) there is a huge skin bag on the head. He knows how to inflate his crested sack so much that sometimes even the head of an animal is not visible behind it.
Seals
Found in the oceans eight different species of fur seals (Arctocephalinae). Only one of these fur seal species is found in the northern hemisphere, while the other seven are found in the southern. They spend most of their time swimming in the open ocean and hunting for food. Fur seals feed on fish and plankton, but also tend to prey on squid and eels. Often these pinnipeds are preyed upon by large aquatic animals such as sharks, killer whales, sea lions, and sometimes adult leopard seals.
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In 1847, Carl Gustav Bergmann, who worked at the University of Göttingen, formulated a rule that, in a simplified form, sounds like this: “In a warmer climate, warm-blooded animals of one or similar species are smaller, and in a colder climate they are larger.”
At first, the conclusions of the German biologist, anatomist and physiologist were received with doubt by the scientific community, but over time it became obvious that Bergman described one of the principles of evolution as precisely as possible.
Indeed, such a pattern not only exists, but is also clearly visible. For example, in an animal that has one of the widest habitats - a wolf. The Arabian wolf, which lives in Oman, Israel and other countries of the Middle East, is a skinny short creature weighing about 15 kilograms. Despite its size, it is a ferocious predator, a biblical symbol of malice and rage.
Northern woods wolf and Egyptian wolf (below)
In Alaska and northern Canada, there are wolves twice as large and five times as heavy. Wolves from the north of India, who raised Mowgli, hardly reached a weight of a quarter of a centner, but the beast on which Ivan Tsarevich rode would have pulled, if he really existed, no less than 60 kilograms, like a hardened wolf of the forest zone of Russia.
A similar situation with the cougar. The variation in weight among individuals living at the equator and in the south of Canada or Argentina is from 60 to 110 and even, in exceptional cases, 120 kilograms.
Changes are noticeable as you climb the mountains. The higher and, accordingly, the colder, the larger the animals. If we consider animals of closely related species, then Bergman's rule is even more obvious: the Malay bear, whose average weight is 45 kilograms, is ten times inferior in weight to the average polar bear.
The polar bear is one of the largest terrestrial mammals of the order of carnivores. Its length reaches 3 m, weight up to 1 ton. It lives in the subpolar regions in the northern hemisphere of the Earth.
The Malayan bear is the smallest representative of the bear family: it does not exceed 1.5 m in length. It lives in India.
Want big differences? Please! Mentally place next to the smallest southern deer, the kanchil from Sumatra, and the largest northern deer, the elk from Kamchatka or Alaska. The difference is simply fantastic: 25 centimeters at the withers and 1200 grams of weight for the first and almost 2.5 meters and 650 kilograms for the second. Such a comparison may not be very correct, but it is clear.
SAVE HEAT
What is the secret why animals grow as the climate gets colder? It's all about thermoregulation. The colder it is, the more important it is to retain body heat, to minimize heat transfer to the environment. After all, maintaining a constant body temperature requires energy, that is, ultimately, food. It needs to be mined, which means spending energy. Why waste it again?
At first glance, the larger the surface of the body, the more heat the living being loses. But it is pointless to consider heat losses by themselves - their relation to heat production is important. Animals not only lose heat, but also produce it, and the larger the volume of the body, the more joules it releases into the atmosphere.
Tiny kanchil deer and elk from Alaska
With increasing body size, the increase in volume outpaces the increase in surface area: in an animal that becomes twice as wide, taller and longer, the body area will increase by four times, and the volume by eight times.
Thus, the ratio of heat loss to its production will be twice as beneficial for the “grown up” animal. In reality, of course, everything is not so mathematically accurate, but the trend is just that.
Of course, as with any rule related to wildlife - that is, to the most complex dynamic systems of many components - there are exceptions to Bergman's rule. Their reasons can be very diverse.
From the scarcity of the food supply, which simply does not allow animals to "gain weight" and forcing them to become smaller, to the resettlement of animals outside their usual range. In such situations, the picture may not be "ideal" due to the fact that not enough time has passed.
Animals that migrated north or south have not yet evolved, because, like most similar processes, in warm-blooded animals, the change in size due to climate is quite fast by paleontological standards, but slower than you can see with the “naked eye”.
However, the largest animals - elephants, hippos, giraffes - live where it is very hot. And this does not contradict Bergman's rule. Extremely abundant food resources are available to such giants. And it would be strange not to use them - since you can eat up to a large size, which is pleasant in itself, and at the same time "bring" yourself out of the threat of predators who cannot cope with the giants.
But these animals are constantly at risk of overheating, since their heat production is huge - therefore, solving the problems of heat transfer, they have to go to all sorts of tricks. For example, sitting in the water most of the time, like hippos, or growing huge ears, like elephants.
POLE CLOSER - EARS SMALLER
Bergman's rule is rarely considered in isolation from another ecogeographical rule, the authorship of which belongs to the American zoologist Joel Allen. In 1877, Allen published a work where he drew the attention of specialists to the relationship between climate and the body structure of warm-blooded animals of related species: the colder the climate, the smaller their protruding body parts relative to its overall size.
Conversely, the warmer the climate, the longer the ears, tails and legs. Again, you don’t have to go far for examples: the fennec fox and the arctic fox. The desert fox is famous for its huge sail ears, while the fox has small ears, barely sticking out of thick wool in winter.
Arctic fox and fox (below)
Indian and African elephants live in a warm climate, and their relative the Siberian mammoth lived in the land of frost. The African elephant has huge ears, the Indian one is noticeably smaller, and the mammoth was completely undignified by elephant standards.
Regularities in the size of the protruding parts of the body are also associated with heat transfer. Through the tails, ears and legs there is an active heat transfer, so in the north or in the highlands it is beneficial to minimize their size. And we are talking here not only about the vain loss of heat, but also about how to keep the body intact. Long tails and large ears can simply freeze so that tissue necrosis develops - this sometimes happens with dogs that the townspeople bring to the tundra from places with a temperate climate. In such cases, the ears and tails of the unfortunate quadrupeds have to be amputated.
Indian elephant
And where it is warm, long-tailed and eared is the most suitable place. Since active heat loss occurs through these organs, they are not a burden here, but, on the contrary, a means of cooling the body, acting like a computer cooler radiator. Let's take an elephant as an example. Its large, vascularized ears receive blood.
Here it cools, giving off heat to the environment, and returns to the body. The same can be said about the processes in the trunk. We do not know, but only assume how energy-intensive it was for mammoths to own a trunk. The ancient animals were saved by the fact that the trunk was with a fairly solid fat layer and, like the rest of the mammoth's body, was covered with thick hair.
Are there any other rules describing the dependence of the appearance of animals on climate? In 1833, that is, before Bergmann postulated his rule, the German ornithologist Konstantin Wilhelm Gloger, who worked in Breslau (now Wroclaw), noticed that in related species of birds (and, as further observations showed, in mammals and some insects too), pigmentation is more diverse and brighter in warm and humid climates than in cold and dry ones.
Those who were lucky enough to get into the repository of the Zoological Museum of Moscow State University could see dozens of wolf skins hanging one after another. Reddish-brown no more than a meter long, fawn a little longer, gray even longer and, finally, huge, human-sized, almost white with a slight admixture of gray and black hairs. Red southern and white northern wolves are an example of Gloger's rule.
Another example is the pink starling, an inhabitant of warm countries, and the common starling, dark with light specks. At first, it was assumed that such a distribution was due to the need for camouflage: among the bright greenery with multi-colored flower petals, it is easy to miss the bird of paradise with its riot of colors in plumage, but the ptarmigan will be in full view.
Pink starling and common (below)
And the rainbow hummingbird will be just as uncomfortable in the tundra - and it is likely that even before it freezes, the bird will be in someone's teeth or claws. The masking version is still not denied, but it turned out that another factor is at work here: in a warm and humid environment, the synthesis of pigments proceeds more actively.
There is an interesting exception to Gloger's rule. This is the so-called industrial melanism, first discovered in England and then in North America. Butterflies that live in places with developed industry can serve as an example of it. Factories threw out smoke and soot, birch trunks and lichens darkened. White butterflies against their background became noticeable, they were eaten by birds.
Those insects survived who, due to a random mutation, turned out to be melanistic (black). Gradually, the number of black individuals in the populations began to reach 90%, but once upon a time 99% were white.
Veniamin Shekhtman
DISCOVERY Magazine August 2014
Since heat transfer in the body occurs through the surface of the body, the thermoregulation of animals depends to a large extent on the ratio of the size of the surface and body weight. Larger organisms have relatively less surface area per unit mass. Then it becomes clear why in closely related species of the same genus or in subspecies of the same species, larger animals are found in the cold parts of the range.
In the northern hemisphere, an increase in the size of animals is observed as you move north, in the southern - to the south. This generalization, made back in 1847 by K. Bergmann, was called Bergmann's rule. There are many examples illustrating Bergmann's rule. Thus, the length of the skull in subspecies of wild boar from Southern Spain is about 32 cm, from Poland - approximately 41 cm, from Belarus - 46 cm, from Siberia - up to 56 cm. The same is observed in wolves, bears, foxes, roe deer, hare and other animals. The largest brown bears live in the northeast of Siberia and Alaska. The smallest hare hares live in Spain, and the largest live in the middle zone of the USSR near the northern border of their range. This rule also applies to birds. For example, the wing length (an indicator of overall size) for horned larks from Canada is 111 cm, from California - only 97 cm; the European oriole is much larger than its relatives from Afghanistan and India. The example of penguins is very typical. The smallest is the Galapagos penguin, living in the tropical zone, only about 50 cm tall. In the temperate climate of Tierra del Fuego, a crested penguin is found, reaching 65 cm. On the Antarctic coast, the largest of the penguins, the emperor, lives - its height is 120 cm or more. However, there are exceptions to Bergmann's rule, which are often explainable. First, they are migratory birds. In winter, they migrate to warmer regions and do not experience the effects of very low temperatures. Secondly, small animals (rodents, insectivores) living in burrows, where the microclimate is relatively milder. Finally, these are island animals that obey specific patterns.
It should be said that V. G. Geptner (1936) drew attention to a very interesting pattern that develops Bergmann's rule: on the continents there are centers of maximum and minimum size of species. In the Palaearctic, the center of the maximum size of animals is Chukotka, and the minimum is Algeria. In the Nearctic, Alaska and Florida, respectively. Developing and supplementing Bergmann's rule is a feature noticed by zoologists in the structure of animals living in cold regions of the globe. It turned out that in homoiothermic animals, subspecies of the same species or closely related species of the same genus have shorter tails, ears, and limbs than their closest relatives from warm regions. The paws and necks of northern animals are thinner and narrower. This phenomenon is called Allen's rule. Its biological meaning is the same: a reduction in the surface of the body relative to its mass and, consequently, a decrease in heat transfer. Allen's rule is convincingly illustrated by the size of the ears and feet of hares. Central Asian sandstone hares have long legs and ears, while European hare and, especially, northern white hare are relatively short-legged and short-eared. Even more telling is the example of foxes. In the hot climate of North Africa, the smallest and at the same time the longest-eared fox, the fennec fox, lives, in our tundra lives a short polar fox with short ears and a muzzle. The European fox is something in between.
Of course, all adaptations cannot be reduced to a reaction only to temperature. In this sense, the influence of climate as a whole is essential, which is confirmed by the so-called Gloger's rule. According to this rule, subspecies of the same species or the closest species of the same genus of homoiothermic animals living in areas with different climates have different colors. In forms from warm and humid parts of the globe, it is darker and more saturated. This is due to the accumulation of eumelanin pigments in the body. In forms from dry and hot regions, light (red, yellow-brown) color predominates, since in those climatic conditions other pigments, pheomelanins, are concentrated in the integument of animals. That is why desert animals have a special color that harmonizes with the substrate, the so-called desert color. There are a lot of examples illustrating Gloger's rule. In essence, the entire desert fauna of our Central Asia and Kazakhstan is subject to this rule.
The dependence of the size, size of the protruding parts of the body and color of animals on geographical distribution is a phenomenon of geographical isomorphism. It is expressed in the fact that the animals of certain countries have a general character of constitution and coloration. This is best illustrated by the desert inhabitants of Asia, Africa and Australia, who, for all the difference in their systematic position, have a similar appearance.
We emphasize once again that the listed regularities are manifested within a species, less often within a genus, but among closely related species.
In addition to these environmental factors, light plays an important role in the life of terrestrial animals. However, there is no direct dependence here, as is observed in plants. However, it is. This is expressed at least in the existence of day and night forms. It should be noted that it is not the lighting itself that plays a role, but the amount of light. In the tropical zone, this factor is not of particular importance due to its constancy, but in temperate and circumpolar latitudes the situation changes. As you know, the length of daylight hours there depends on the time of year. Only a long polar day (its duration is several weeks) can explain the fact that migratory birds of the Far North have time to bring out and feed their chicks in a short time, since insects serve as food for them, and they are active around the clock.
An abundance of light pushes northward the frontiers of life for many species. The short winter day does not allow even cold-loving birds to get enough food to compensate for energy costs, and they are forced to migrate to the south.
A powerful factor regulating the life cycle of a number of animals is the length of daylight hours. The phenomenon of photoperiodism, to the explanation of which the Soviet zoologist A. S. Danilevsky made a significant contribution, determines the development of a certain number of generations in insects during the year, as well as the possibility of expanding the ranges of animals to other latitudinal zones.
Photophilicity or photophobicity of animals can be an indicator of their relationship to the climate. So, many desert forms openly appear only at dusk or at night, not because they are "convinced photophobes", but, apparently, due to the fact that there is more water vapor in the air at night. In other words, in hot and dry regions, the "day" and "night" climates are different. This allows both real xerophiles and animals that require higher moisture to live there.
Wind is one of the important climatic factors. There are places on the globe where it blows constantly and with great force. This is especially true for sea coasts and islands. Here, as a rule, there are no flying insects - butterflies, flies, small bees, wasps, while they live on the nearby mainland. The absence of these insects entails the absence of bats that feed on them. For oceanic islands, wingless insects are typical, which reduces the risk for them to end up in the sea. Thus, the wind to a certain extent determines the composition of the fauna.
In turn, tube-nosed birds - albatrosses, petrels, frigatebirds - are confined to areas with constant winds. These birds are able to soar above the water, using air currents and without wasting muscular effort on movement.
The nature of the substrate, i.e. soil, also plays an important role in the life of land animals. In this case, not only the chemistry of the soil is important, but also its physical properties. There is a dependence of the distribution of animals on the presence of salts in the soil. Arthropods are the most sensitive to soil salinity. For example, beetles of the genus Bledius, like many ground beetles, are usually found only in saline soils. Such animals are classified as halophilic. Many animals are also sensitive to the type of rocks. Limestone rocks, for example, are inhabited by molluscs whose shells are made of lime.
However, more often soil chemistry has an indirect effect on animals, in particular, through fodder plants. The role of the food factor in the life of animals is well known. None of the organisms can do without food, because at the expense of nutrients they receive energy and material for building their own body. As already mentioned, animals in general exist at the expense of plants. Heterotrophs use only ready-made organic compounds. It should be noted that the species diversity of plants and animals on land creates a number of differences that are specific to terrestrial ecosystems.
Keeping warm is very important for those animals that live in cold climatic zones, so many of them are noted for their fitness for such conditions in physique.
Basic data:
Change in body shape. In many inhabitants of cold regions, the shape, size and proportions of the body differ from the shape, size and proportions of the body of animals of the same species inhabiting warm regions. This body structure is a sign of better adaptation to the regulation of heat transfer. This fact is explained by the example of two rules.
Bergman's rule. Obviously, animals that live in cold climates have a rounded body. According to Bergaman's rule, a rounded body shape helps to retain heat better. An excellent example illustrating this rule is the cylindrical bodies of mammals living in cold water, in particular seals.
Bergaman's rule says that among animals of the same species living in a large range, the largest individuals are found in cold regions. The closer to the south, the smaller their size. So, for example, the most mobile tiger is the Amur tiger. Smaller - Bengali. And quite a small one - the Javanese tiger. So, in accordance with the rules, large wolves should live in the Arctic.
Allen's rule. According to Allen's rule, in animals inhabiting cold areas of the range, the protruding parts of the body (limbs, tail, auricles) are smaller than in representatives of the same family living in warm areas. The dimensions of the body are reduced in order to reduce heat transfer and prevent unnecessary heat loss. So, an ordinary fox has a short body, limbs and tail, a convex forehead, shortened ears and mouth. The red fox has a more elongated body, a long tail and muzzle, as well as ears, protrude strongly. And the steppe fox has long limbs and huge ears. Animals need large ears to improve heat dissipation and to prevent overheating of their bodies.
OR DO YOU KNOW THAT...
Chinchilla has a very thick coat, because up to 40 hairs grow from one hair follicle.
During the winter thaw in the Arctic latitudes, it rains, after which the wet wool of musk oxen often freezes, forming an ice shell that prevents the animal from moving.
1 cm2 of northern fur seal skin covers up to 50,000 hairs.
Reindeer often make long journeys in search of shelter from cold winds, they try to keep warm by pressing their bodies against each other.
Mammals living in cold regions maintain a constant body temperature, primarily due to the air gap present in their coat. Many animal species have a thick layer of fat under the skin. Some species are saved from the cold with the help of a special body structure.
North of the Arctic Circle
The coldest part of the mammalian range is the Arctic. With the exception of the polar bear, which lives even at the North Pole, most of the species live in the southern regions. Many inhabitants of the Arctic have thick, long, and usually white coats. Their fur coats are arranged according to the principle of double window frames, between which there is air - a thermal protective layer. In the summer, the coat of most species thins. The polar bear wears a white outfit with shades of yellow throughout the year. The sun's rays penetrate through the white hairs to the bear's skin and heat it up. The bear's coat consists of a thick undercoat, so the bear's skin remains dry even while swimming in icy water. In addition, a thick layer of subcutaneous fat also protects it from the cold.
The wolverine also has a very thick coat. Since ice crystals never form on the wolverine's fur, the Eskimos sew a lining for clothes from its skins. Other "frost-resistant" animals, musk oxen, grow hair from a thick undercoat 50-70 cm long. Both layers have excellent properties for retaining heat and protect the animal even in the most severe frosts. The musk ox molts during the short Arctic summer.
Thermoregulation IN THE MOUNTAINS
In mountainous areas, nighttime temperatures are usually much lower than daytime temperatures. Mammals living high in the mountains must adapt not only to seasonal temperature fluctuations, but also to daily ones. Wind, rain and snow in winter are not very pleasant phenomena, so most of the highlanders, like the inhabitants of the Arctic, have thick fur. Chinchillas, Vicuna, guanacos, llamas and alpacas living in the Andes have very warm coats. People shear guanacos, llamas, vicunas and alpacas for warm wool. In forested mountains, the difference between day and night temperatures is not so great. This is used by many species of mountain goats and rams, which descend to these places from a higher altitude for the winter.
Thermoregulation IN WATER
Some marine mammals live near the Arctic and Antarctic Circles, while walruses are found only in the Arctic. Some species of pinnipeds live off the coast of Antarctica, constantly being in icy water. Narwhal and beluga whales spend their entire lives here, and gray, humpback and blue whales appear in these regions in the summer. In cold water, heat transfer is much more intense than in cold air. A person who finds himself in such conditions is only able to live for a few minutes. The cylindrical shape of whales and seals prevents excessive heat generation, and a thick layer of subcutaneous fat helps them maintain a constant body temperature when they are in icy water. The thickness of the fat layer, depending on the type of animal, ranges from a few centimeters to half a meter. In addition, pinnipeds have a special circulatory system - it acts as a heat exchanger. The principle of its operation is based on the fact that the vessel through which blood enters the limb is entwined with a network of small vessels that carry blood from the limb. With a steady heat exchange between the opposite blood flows, a minimum cooling of the blood that circulates inside the body of the animal is achieved.
PROTECTION FROM THE COLD
With the onset of hard frosts, a layer of snow for many animals becomes an excellent shelter that retains heat. Such small mammals, such as lemmings, dig complex underground corridors covered with a thick layer of snow on top. Ermine also hides underground in winter. A giant brown bear living in Alaska sleeps in a den in winter, and male polar bears hide under the snow only during snowstorms, while pregnant females hibernate in a snowy lair. The female polar bear climbs into the den and curls up into a ball. The lair is covered with snow. In this case, the snow forms a kind of insulating layer. Wolves, reindeer and moose are not afraid of frost. Moose do not rush into hibernation, but take energy from fat reserves, which they have worked up in summer and autumn. They move very little and only in the very cold they seek shelter in thickets of plants and other protected places. Chipmunks and many other small mammals hibernate in winter.
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