What animals eat eucalyptus. What animal eats only eucalyptus leaves? Cries during mating season

Quartl/Wikimedia Commons

Scientists have sequenced the entire koala genome for the first time and analyzed more than 26 thousand active genes, reports the paper. Nature Genetics. This allowed scientists to understand why marsupial bears can eat poisonous eucalyptus leaves without harm to themselves, how they chose a suitable diet for themselves, and how they learned to protect cubs and adults from infections.

Koala ( Phascolarctos cinereus) today the only representative of the koala family that lives in Australia. Koalas are the closest relatives of wombats, their common ancestor lived about 30–40 million years ago. In ancient times, there were 15-20 species of these animals on the continent, and the current species appeared about 350 thousand years ago. To date, three subspecies are known. One of them lives in Queensland, in the northeast of the continent, the other two - in the south and southeast of the country. Previous studies (though conducted more than 20 years ago) showed that two of the three subspecies have low genetic diversity and a high percentage of inbreeding.

The female koala gives birth to an underdeveloped baby after a 35-day pregnancy, and the baby spends the next six months in the mother's brood pouch. Koalas are very selective in food: they feed almost exclusively on eucalyptus leaves, and out of 600 species of eucalyptus, they prefer about 30. Animals get almost all their water from leaves, so they include in their diet those types of eucalyptus whose leaves contain at least 55 percent of water. Since the leaves are low in calories, animals need to eat up to 400 grams of leaves per day and save energy. They sleep about 20 hours a day and eat most of the remaining four hours. Eucalyptus leaves are not a very attractive food, not only because of their low calorie content. They contain compounds that are extremely poisonous to most other animals. Koalas adapted to them, and thus practically avoided food competition. However, how they adapted to poisonous food, and how they distinguished suitable trees among the huge variety of eucalyptus species, was until now unclear.

To answer these and other questions (for example, how koalas protect themselves from infections and how the species can be preserved in the future), scientists from the Koala Genome Consortium sequenced the entire genome of the marsupial bear. The team of researchers, currently consisting of 54 scientists from seven countries under the leadership of Dr. Rebecca Johnson, began work in 2013 and has already published part of the results.

In the new work, scientists present directly the results of genome sequencing and analysis of the 26,558 active genes that make up it. The koala genome turned out to be larger than the human genome (3.42 versus 3.2 billion base pairs), but consists of fewer chromosomes (16 versus 23 pairs).

Scientists have discovered how marsupial bears adapted to their poisonous diet. They turned out to have much more genes encoding proteins from the cytochrome P450 family than other animals. These enzymes oxidize various substances, converting them into water-soluble metabolites that are quickly excreted in the urine. It turned out that koalas produce cytochromes in many tissues, including the liver. However, the protection also had a downside - cytochromes quickly break down antibiotics given to sick koalas.

Genes also made it possible to explain the ability of animals to recognize the desired species of eucalyptus. Koalas were found to have 24 genes responsible for recognizing the bitter taste - the largest number among Australian marsupials. In addition, they turned out to have six genes encoding vomeronasal receptors that can detect the smell of not very volatile substances. For comparison, the marsupial devil and the gray short-tailed possum each have one such gene, while the platypus and wallaby do not have them at all. Koalas are also able to sense the “taste of water” - to recognize the water content in eucalyptus leaves. They learned this by increasing the number of genes for the protein aquaporin 5, which forms pores in the cell membrane through which water enters cells.

Researchers have found that koalas protect their cubs from infections while they are in their pouch using breast milk. It contains enzymes specific only to koalas that have an antimicrobial effect. They protect young animals from a number of bacterial and fungal infections, including chlamydia Chlamydia pecorum which cause diseases of the eyes and genitourinary system. Adult koalas are saved from infections with the help of numerous proteins of the immune system - immunoglobulins, proteins of the major histocompatibility complex, T-lymphocytes.

In addition, scientists have found new genetic markers and with their help they are convinced that subspecies, which, according to old studies, had low genetic diversity and a high percentage of inbreeding due to the isolation of populations, are actually mixed with each other and have quite a lot of genetic diversity high.

More details about the habits and personal life of koalas by Zhenya Timonova in one of the episodes “Everything is like animals.”

Ekaterina Rusakova

Few people can remain indifferent when contemplating a charming animal that looks like a little bear. Although the Australian resident has nothing to do with them. Like many other inhabitants of Australia, the koala is a marsupial mammal. It was first described in 1798, when it was found in the Blue Mountains (Australia). Since then, the animal with a wide muzzle and small eyes, a curved nose, soft and silvery fur, and shaggy ears has been loved by many.

Koalas are descended from their closest relatives, wombats. They are similar to them, but differ in softer and thicker fur, their ears are slightly larger, and their limbs are longer.

The animal's sharp claws help it easily move along tree trunks; the shape and size of its limbs also contribute to this. The hands of the front paws have two thumbs, which are set to the side, with three more fingers located next to them. This design of the palms helps the animal to easily grasp branches and tree trunks and hold onto them tenaciously, and for young animals to hold on to their mother’s fur. The koala, clutching a branch, sleeps on a tree, and it can even be supported by one paw.

Interestingly, the papillary pattern found on the fingertips of koalas is very similar to human fingerprints; even an electron microscope would have difficulty detecting the differences.

The size of koalas is very diverse. For example, a female living in the north can weigh 5 kilograms, and a male living in the south can weigh 14 kilograms.

The photo shows a koala eating eucalyptus leaves.

Koalas eat only the bark and leaves of eucalyptus trees. There are more than 800 species of these trees in the world, but these animals only eat the bark and leaves of 120 of them. Interestingly, these trees are poisonous to most animals. Due to their unique digestive system, colas eat them without tragic consequences. But the furry animals try to choose eucalyptus trees growing on fertile soils along river banks. The leaves and branches of such trees contain less poison. Eucalyptus trees growing on poor, dry soils contain more toxic substances.

The daily diet of this animal is 500–1100 g of food. At the same time, they mainly feed on softer and juicier young leaves. Koalas hardly drink water, since eucalyptus leaves contain more than 90% of the liquid they need. Animals drink water only when they lack moisture in the leaves or are sick.

The koala is almost motionless 18–20 hours a day. At this time, she clasps branches with her paws, sleeps or moves along the trunk in search of food, or chews leaves, which she puts in the inside of her cheeks during feeding.
She jumps from tree to tree mainly to find food or escape from danger. Another unique ability of this animal is that it can swim. Koalas are quite slow, this is due to their feeding habits, since the leaves contain little protein. In addition, koalas have a low metabolism, it is 2 times slower than that of other mammals.

Sometimes, to replenish the need for microelements, koalas eat soil.

Reproduction of koalas, birth of cubs

The breeding season for koalas is from October to February. At this time, they gather in groups that consist of several females and one adult male. The rest of the time, each female lives in her own territory and leads a solitary lifestyle.

Koalas are fairly quiet animals. Loud calls can only be heard during mating season. Eyewitnesses say that these sounds are similar to the grumbling of a pig, the creaking of door hinges and even the snoring of a drunken person. However, females really like these sounds, and they respond favorably to the calling sound of males.

Another unique distinguishing feature of these marsupial cubs from other animals is their reproductive organs. The male has a forked penis, and the female has two vaginas. Thus, nature made sure that this species did not become extinct.

Pregnancy in koalas lasts 30–35 days. Most often, only one calf is born, which weighs 5.5 grams and has a height of 15–18 millimeters. Although there are also cases of two births. The baby stays in its mother’s pouch for six months, during which time it feeds on her milk. Over the next six months, he gets out of the pouch, tenaciously clings to the mother’s fur on her stomach and back, thereby “traveling” through her body.

For the next 30 weeks, he eats semi-liquid maternal excrement, consisting of a pulp of half-digested eucalyptus leaves. Here are microorganisms that are valuable for the baby and necessary for his digestive process. After a month, the cubs become independent, but are still with their mother until they are 2–3 years old.

Males reach sexual maturity at 3–4 years, and females at 2–3. They reproduce once every 1 or 2 years. Life expectancy is 11–12 years, although there may be exceptions; there are cases where koalas lived for 20 years.

In the wild, the marsupial has no enemies, most likely because its meat smells like eucalyptus. Animals are tamed quite quickly, they are condescending towards the person who takes them in their arms. But at the same time, we must not forget about the sharp claws of the animal, so you need to stroke it carefully.

A koala can be like a child; when the animal is left alone, it can cry and yearn. In the wild, drought, fires, and poachers are destroying these touching animals. Cutting down eucalyptus trees also contributes to their destruction.

The slow motion world of koalas and sloths

They are in no hurry. While antelopes race across the savannah, squirrels and weasels flash among the branches, and kangaroos clatter through the bush, these animals spend their time in a half-asleep state in the treetops.

Sometimes koalas may seem very nimble. For example, when fighting with dogs or during mating games. At such moments, the Australian “teddy bears”, suddenly showing an agility that is completely inconsistent with their appearance, look strikingly unusual.

But they spend most of their time alone, sleeping or sitting completely motionless, moving only their jaws. The life of koalas drags on slowly and monotonously. This is the price to pay for the opportunity not to compete with anyone for food resources, eating poisonous eucalyptus leaves.

Eucalyptus leaves are bad food. They have almost no protein, they are hard and fibrous, and, worst of all, they contain a lot of toxic phenols and terpenes (the main components of resins and essential oils), coumaric and cinnamic acid, and hydrocyanic acid is also present in the leaf petioles. But this resource, although of little nutrition, is extremely extensive, because eucalyptus trees, being very unpretentious trees, form forests even where other trees do not survive. It would be strange if such a food source did not attract any “gastronomic extremes.”

Only 120 of the more than 700 least poisonous species of eucalyptus are suitable for koalas to eat, and in order to distinguish edible leaves from others, the animals resort to an unusually developed sense of smell. Since all eucalyptus trees belong to the same genus, their smells are very similar, and koalas try to eliminate the slightest mistake.

If you hold leaves edible for koalas in your hands and then offer them to “teddy bears,” they will not eat them: the smell is different from the standard one, and the animals will not take risks. Such “stubbornness” is associated with many cases when koalas died in captivity, refusing food that they certainly ate in freedom, but which for some reason acquired an uncharacteristic smell.

Although the koala diet is rich in essential oils, runny noses are not uncommon in these animals: they often suffer from inflammation of the nasal sinuses, from which many die, especially in cold winters. It even reaches the point of epizootic respiratory tract infections.

So why is the koala world so slow? Due to the fact that eucalyptus leaves are poisonous, you should not eat a lot of them so that toxins do not accumulate in large quantities in the body. In a day, a koala rarely eats more than half a kilogram of leaves, which is not much for a herbivore weighing more than 10 kilograms. But, since the leaves have little nutrition, you need to digest them as best as possible so that nothing useful is lost.

As a result, the koala eats slowly, digests slowly, and its entire metabolism is extremely sluggish. The leaves are chewed very thoroughly, grinding into a pulp, which accumulates in the cheek pouches, where it undergoes primary processing by enzymes contained in saliva.

Then it enters the stomach, and from there into the intestines. Its section, which serves for processing coarse fibrous food, is the cecum, part of which was reduced in our appendix; in koalas it reaches two and a half meters in length. Here, symbiotic bacteria decompose cellulose, and this is a long and energy-consuming process. To save energy, the animal sleeps most of the day - 16-20 hours.

What do these marsupial “bears” do when they are not sleeping? Mainly food, they even drink only in drought or during illness, usually making do with the moisture contained in the leaves. These sweet creatures, alas, are not very interesting for the observer, because, adapting to a low-calorie and toxic diet, they sacrificed a lot, including the size and complexity of the brain, and, consequently, the complexity of behavior.

The brain is an extremely “expensive” organ in the energetic sense; it is not easy to feed it, because it consumes up to 20% of the energy received by the body. Therefore, when possible, it is more profitable for animals to reduce their brain size. This even happened to humans: between 25 and 10 thousand years ago, our brains shrank by more than 100 cubic centimeters.

In koalas, which, like all marsupials, have never been particularly intelligent (marsupials lack a corpus callosum that connects the hemispheres of the brain), the brain has shrunk so much that almost half of their skull is occupied by cerebrospinal fluid. In the brain itself, only the olfactory lobes are perfectly developed, and everything else is tiny. As a result, koalas spend most of their lives sitting in trees and basically doing nothing. They are unsocial, silent, and actively communicate with their own kind only during the mating season, when males mark territory, fight with rivals and collect a harem of several females.

Mating games take place right on the tree and look very funny. At the end of the breeding season, the harems disintegrate, and the females, after a month of pregnancy, give birth, as is customary with marsupials, to “underdeveloped” cubs, which are carried for another six months in the pouch.

In order to digest eucalyptus leaves, the baby koala must acquire the appropriate intestinal microflora, which does not appear by itself. The cubs lick the mother's excrement, which changes for about a month, turning into a paste of semi-digested leaves containing cultures of bacteria necessary for the baby. Growing up, the koala cub leaves its mother and begins to lead an independent life - monotonous and slow, but lasting for 15, or even 20 years.

Surprisingly, even after a collision with a person, such a defenseless creature still thrives. Even despite the fact that in the 19th - early 20th centuries, koalas were exterminated en masse by hunters (and hunting animals that are not afraid of anyone, do not run away or hide, is as easy as shelling pears), harvesting up to two million skins a year, until 1927 th, when hunting for them was prohibited. Of course, in the modern world many dangers await these animals. For example, ticks accidentally imported from Japan.

And when, during the mating season, koalas come down from the trees and actively move along the ground, they run the risk of being hit by a car while crossing the highway or being caught by dogs, who will not miss the opportunity to hunt such an animal. Even though koala meat is completely inedible, which reliably protected it from local predators. Many enthusiasts are involved in rescuing wounded koalas, delivering them to special centers or regular veterinary clinics.

Koalas' closest relatives, wombats, also have a slow metabolism, but live on land and are less picky about food.

LAZY MASTERS OF SYMBIOSIS

Much further north than koalas, in South America, live creatures with an equally slow metabolism. These are two-toed and three-toed sloths. Living surrounded by numerous predators, not constrained by a strict diet, they nevertheless preferred the inaction glorified by the Taoists. The lifestyle of sloths is in many ways similar to that of koalas. For more than half a day, sloths sleep, completely relaxed, hanging on tree branches, on which they are held with the help of long curved claws, externally (and functionally) similar to the “claws” of installers and rural electricians.

It’s amazing that the “hang on and don’t shine” strategy allowed sloths, which feed on jaguars, harpy hawks and other hunters of seemingly easy prey, to proliferate so much that in some areas of their habitat the biomass of sloths accounts for two-thirds of the total biomass mammals. In one square kilometer of rain forest there are sometimes over 750 sloths. This is an incredible density for large mammals! Animals hang motionless in the treetops, blending in color with the foliage, and predators simply do not notice them.

Sloths have four times less skeletal muscle than other mammals of the same size. This is both a plus - less energy is spent on maintaining muscles - and a minus: once on the ground, the “weak” sloths can neither offer real resistance to anyone (although sometimes they scare away enemies by hissing and waving their long clawed paws), nor escape , especially since they are not able to walk normally and step on the outer part of their claws.

Sloths were once a thriving family, most of whose members were diurnal (unlike today's, active at night) and highly active animals. Megatheriums, the ancestors of modern sloths, were three meters tall and weighed half a ton. However, everyone died out except those who made secrecy and physical inactivity their survival strategy.

Sloths' adaptation to a sedentary, hanging lifestyle has affected their entire anatomy and physiology. Their brain, like that of koalas, is relatively small (although much larger: after all, sloths are placental mammals, not marsupials), the convolutions are strongly smoothed, and only the olfactory parts of the brain are well developed.

Like koalas, sloths do not drink water, content with licking off the dew. Internal organs are displaced, for example, the liver is adjacent to the back. Unlike all other mammals, the number of cervical vertebrae in sloths is not necessarily seven, but can be up to nine. A large number of cervical vertebrae will give the animal the opportunity to tear off foliage over a larger area, moving only its head.

The body temperature of sloths is not constant; on cool nights they cool down to 12 °C, and on a hot day they can heat up to 35 °C without harming their health. Sometimes they gather in groups for warmth and hang close to each other. It is believed that they mate there. Unlike koalas, sloths eat a wide variety of plants, not only foliage, but also buds, flowers, and young shoots.

Like most herbivores, they do not refuse protein foods, if they are lucky enough to feast on insects or lizards. And in times of famine they can even feed on algae that live in their fur.

Blue-green photosynthetic algae are normally not a food supply, but camouflage. The greenish fur, which grows on sloths not from front to back, but vice versa (that is, by stroking the animal with the usual movement from head to tail, you stroke it against the grain), perfectly camouflages the animal, making it almost invisible in the crown of the tree. In addition to algae, they also have other symbionts. The sloth, like the koala, coexists with abundant intestinal flora for mutual benefit.

And in his fur (and only there) fire butterflies settle Bradipodicola hahneli. Adult insects feed on algae, and the larvae develop in sloth excrement. For reasons that are not entirely clear, these animals relieve themselves only on the ground, where they go down about once a week (they have a huge bladder). To excrete, the sloth digs a hole at the roots of the tree on which it lives and fertilizes it with its feces, thus entering into a kind of symbiosis with the tree. It is a pity that the numbers of these mammals are declining. This happens due to the destruction of tropical forests, in which sloths feel at ease, but cannot exist outside of them.

Alas, sloths also have roommates that both they and we humans could easily do without. These are protozoa, the causative agents of leishmaniasis, a dangerous disease.

Why is it that when both sloths, who live up to 30 years (longer than other mammals in the same places), and koalas thrive in their slow-moving world, virtually no one has followed suit? Why do other mammals prefer to be swift and agile, despite the high “energy cost” of an active lifestyle? In order to allow yourself to live slowly, with atrophied muscles and a weak brain, you need to find yourself in a very unusual situation. One where giving up the desire for speed will be beneficial.

For example, it will provide an opportunity to develop an unclaimed food base without the risk of becoming someone’s prey, or, taking advantage of the symbiosis with algae, to hide from predators who will not be able to notice the motionless green animal in the foliage. Such lucky coincidences probably happen extremely rarely, and those who tried to get out of the “race for speed” without such favorable initial conditions disappeared, leaving no descendants.

Magazine Discovery January 2013

The koala is an animal with fluffy fur, cute big ears and a hilarious expression on its face. It is easily tamed and easily tolerates all conditions of captivity. When the owner leaves, the koala cries like a small child. But as soon as you pet him and talk kindly, he calms down.

So why do few people keep koalas at home?

It's all about the food. Animals eat eucalyptus leaves. And that’s not all, but only a little more than a hundred species out of 800 eucalyptus trees on Earth. They eat about 1 kg of leaves per day.

This herbivore has a special digestive tract structure that allows it to process coarse fibrous leaves. Moreover, the main digestion occurs in the cecum, which is more than two meters long. In humans, this process is only up to 80 mm long.

Almost no one eats eucalyptus leaves from animals because of their low nutritional properties and, most importantly, toxicity. Any animal that eats a leaf with terpenes, phenols, and in the fall with the resulting hydrocyanic acid, will be poisoned. And at least something for a koala!

Four reasons why koalas are not poisoned by eucalyptus leaves:

Over many years of evolution, the koala's body has become resistant to poisons. The main organ of any living organism responsible for processing poisons is the liver. In koalas it is so powerful that it can neutralize harmful substances.

They eat only young leaves. They do not contain many toxins.

Only those species that have a lower concentration of poisons are eaten.

They choose groves that grow in rich nutrient soils for food. They also contain lower amounts of phenolic compounds.

Trees are their main place of residence. You will never see a koala running on the ground. Because in just two hours at night they will eat their quota of leaves, and the rest of the day they sleep on a branch, leaning against the trunk.

This sedentary lifestyle is also explained by the nature of the diet. Where can the animal get energy if eucalyptus leaves contain almost no protein? He carefully chews the leaves into a pulp and stores it in pouches behind his cheek. The speed of food digestion is slowed down, so metabolism also takes a long time.

Koalas might be happy to run, but they simply don’t have the strength to do it. Constant drowsiness and slowness are the characteristic features of his behavior.