The animal eats eucalyptus leaves. Koalas are the original representatives of the living world of Australia

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 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.

I wonder what 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. One more unique ability 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 the 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 one distinctive feature The difference between these marsupial cubs and other animals lies in the 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 holds on 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.

IN puberty males enter 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 wildlife The marsupial has no enemies, most likely because its meat smells of 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 koala is a small, cute, gentle animal that lives only on one continent - Australia. In the Aboriginal language, the word "koala" means "does not drink." The animal actually practically does not drink water, being content with the moisture contained in eucalyptus leaves. His Greco-Latin family name "Phascolarctos" means " marsupial bear" Koala really for a long time called a bear, but it is not a bear, and it has nothing to do with bears, except that it looks like a fluffy teddy bear. In fact, the koala is a marsupial; it is the only modern representative of the Koala family (Phascolarctidae).

Today the koala is the most beloved marsupial animal by Australians, one of the recognized symbols of Australia, but this was not always the case. The first European settlers killed millions of these defenseless animals for their thick fur. However, deforestation of eucalyptus forests, drought and fires posed an even greater threat to the survival of the species. The threat to koalas peaked in 1924, when more than 2 million pelts were exported. By then, koalas had disappeared from South Australia and most of Victoria and New South Wales. As a result of public protest, a ban on hunting was introduced starting in 1944, and only 10 years later their population began to gradually recover. Currently, in a number of areas, in particular in the south of its range, the koala has again become normal look, and the IUCN lists this animal as being of Least Concern. However, intensive deforestation poses a threat to northern populations.

Description and photo of koala

The appearance of koalas is characteristic: the body is short and stocky, the head is large, round, with small eyes, large fluffy ears and a patch of bare skin on the nose. The tail is rudimentary, almost invisible from the outside. The color of the thick and soft fur on the dorsal side varies from gray to reddish-brown; There is white fur on the chin, chest and inner surface of the forelimbs. The ears are bordered with long white hair, the rump is covered with white spots. In the north of their habitat, the fur of the animals is shorter and less common.

The koala's body length is 70–85 cm, weight 7–12 kg. Males are more massive than females, they have a wider muzzle, and the size of the ears is smaller. In addition, males have a scent gland on their chest, with which they leave marks on trees within their territory. Females have a pouch with two nipples that opens back.

The koala is remarkably adapted to being sedentary. tree image life. Its body is covered with thick fur, which protects the animal from bad weather and temperature fluctuations, which is very important - after all, koalas do not have any shelters or shelters. Large paws are equipped with strongly curved claws, thanks to which the animal can easily climb onto the very tall tree with smooth bark. The photo shows a good view of the powerful and strong claws of a koala. If an animal sticks them into a tree, it will not fall down.

When climbing a eucalyptus tree, the koala grasps the trunk with its strong front paws, moving its body upward and at the same time pulling up its forelimbs. On the hind legs, the first toe is opposed to the others, the second and third are almost fused. On the front feet, the first and second toes are opposed to the others, providing a strong grip when climbing. The soles of the paws are bare, with a palpable pattern. An interesting fact is that koala fingerprints are almost identical to human ones.

The koala has a total of 30 teeth; the upper jaw retains three pairs of incisors and rudimentary fangs. The teeth are well adapted to feeding on eucalyptus leaves containing large number fibers Chewed leaves undergo microbial fermentation in the cecum, which is the longest in relation to body length of any mammal (its length is 1.8-2.5 meters).

In the photo, a koala habitually eats the leaves of his favorite eucalyptus tree.

The koala's brain, compared to its body size, is one of the smallest among mammals, only 0.2% of its total body weight. Scientists believe that this is due to adaptation to a low-calorie diet.

Where does the koala live?

Koalas are found only in Australia, where they are found over many hundreds of thousands of square kilometers in the east of the continent from northern Queensland to southern Victoria. Populations of these marsupials are often separated from each other by wide areas of cleared forests. Koalas have chosen moist mountain forests in the south, vineyards in the north, coppices and semi-desert landscapes in western Australia. Population density depends on the productivity of the land. In the south in rain forests it reaches 8 animals per hectare, and in semi-desert zone Only one individual can live on an area of ​​100 hectares.

How does a koala live in the wild?

The life of koalas is closely connected with trees of the genus Eucalyptus, in the crowns of which they spend almost all their time. They spend most of the day (18-20 hours) sleeping, feeding takes 2-3 hours, and the rest of the time the animals just sit. Only occasionally do they descend to the ground to run from one tree to another.

Koalas usually sleep during the day, but at night they are busy leisurely absorbing eucalyptus leaves. The movements of the animals are usually very slow and lazy, although a frightened animal can move very quickly.

Koalas lead sedentary image life. Most are loners; they rarely live in pairs. Adult animals occupy certain habitat areas. IN favorable conditions these areas are relatively small: a male can occupy only 1.5-3 hectares, females even less - 0.5-1 hectares. In areas poor in vegetation, the male’s area can be more than 100 hectares. The territory of a dominant male can overlap the areas of up to 9 females, and also the areas of subordinate males. Each animal has several favorite food trees on its individual plot.

In nature, the koala lives up to 10 years, the maximum known life expectancy in captivity is 18 years.

What do koalas eat? Eucalyptus diet

The leaves of the evergreen eucalyptus provide koalas with a constant source of food. An adult eats about 500 grams of fresh leaves per day, and although more than 600 species of eucalyptus trees grow on the Green Continent, the koala eats leaves of only 30 of them. In different regions, preference is given to different types eucalyptus trees, but mainly those that grow in conditions of high humidity.

Such a diet may seem dubious at first glance, because eucalyptus leaves are inedible or even poisonous to most herbivores. They are poor nutrients and contain a lot of indigestible fiber, as well as toxic phenols and terpenes. However, these animals have several adaptations that help them cope with such inedible food. They do not eat some leaves at all; the toxic components of others are neutralized by the liver and excreted from the body. Since the diet is low in calories, koalas sleep up to 20 hours a day. They conserve water and, except in the hottest weather, obtain the necessary moisture from the leaves they eat. Thus, evolution gave koalas a food source available all year round, and also saved them from food competition.

Continuation of the family line

Koalas are polygamous, they have small quantity males account for the majority of matings. But the details of the distribution of matings between dominant and subdominant animals are not fully understood.

Both female and male koalas reach sexual maturity at two years of age. From this time, females begin to reproduce, while males begin breeding 2-3 years later, when they become large enough to compete for a female.

The breeding season is in spring and early summer (September–January). At this time, males move very long distances, and clashes often occur between them when they meet. During “weddings” the “grooms” constantly roar. These calls, consisting of loud inhalations followed by bubbling exhalations, are designed to attract the attention of brides and also warn competitors. The call of one male usually evokes a response from nearby relatives. During this period, males often mark the boundaries of their territory by rubbing their chests against trees.

The female brings one litter per year of one, less often of two cubs. Pregnancy lasts 35 days. The baby is extremely small at birth - its weight is less than 0.5 kg. The newborn climbs into the pouch, where it is securely attached to one of the two nipples. The small koala spends approximately 6 months in the pouch, where it grows and develops. The mother carries him on her back for some time.

From the age of seven months, the baby switches to feeding on a special gruel made from semi-digested eucalyptus leaves, secreted digestive system mothers, getting used to the food of adult animals. A young koala becomes independent by the age of 11 months, but usually continues to stay close to its mother for several more months.

Conservation in nature

In nature, the koala has practically no enemies; predators do not favor its meat, apparently due to the fact that it has a strong eucalyptus smell. Despite this, animals are often considered vulnerable. Although no one has officially counted these marsupials, according to unofficial data, their number ranges from 40 thousand to 1 million. Habitat destruction is the main threat to most koala populations in the northern part of their range. But the situation is much more serious in the semi-desert regions of central Queensland, where about 400 thousand hectares are cleared annually for pastures and other agricultural needs. And although environmentalists are sounding the alarm and trying to stop the destruction of forests, the problem remains relevant in the agricultural areas of central Queensland.

These funny little animals, photos of which can be seen in various publications about animals, are of interest not only to ordinary lovers unusual inhabitants our planet, but also scientists. Where does the koala live? What does it eat? Which lifestyle do you prefer? We will not leave any of these questions unanswered in our article. We hope that many facts from the life of these charming creatures will be of interest to you.

What continent does the koala live on?

The koala is an animal endemic to Australia. This is the original representative of the Koala family. They live on eucalyptus trees. The koala is a marsupial belonging to the two-incisor order. Its range is mainland Australia, but only its eastern and southern parts.

Before the arrival of Europeans, animals were common in the north and west. Much later, koalas were settled by humans on the territory of Kangaroo Island. Small animals that look like teddy bears arouse universal sympathy. These marsupials spend almost their entire lives in trees, deftly walking along the branches. A koala can live in one tree for many days, and only after clearing its leaves does it change its “home”.

You can’t run far on the ground on short legs, which is why slow koalas often die under the wheels of cars or become easy prey for wild dingoes. The animals devote the night hours to feeding, and the rest of the time they sleep, comfortably sitting in the fork of the branches. Koalas sleep very lightly and wake up at the slightest rustle. They prefer to live alone. Each adult animal has its own grounds, which it marks with secretions of odorous glands. Such a male's area sometimes coincides with the possessions of several females.

What does a koala look like?

These are small animals: their body size is from sixty to eighty centimeters, with a weight of six to fifteen kilograms. Koalas have a very small tail: it is almost invisible behind their lush fur. The animal has funny round ears that are completely covered with fur.

It is impossible to describe what a koala looks like without mentioning the fur of these animals. It is soft and thick, quite durable. The color may vary, but most often shades predominate gray. It is much less common to find an animal with bright red-red fur.

Lifestyle

We found out where the koala lives and what it looks like. It's time to tell how these animals live. Koalas are animals that lead a measured and leisurely lifestyle. They sleep almost the entire day (from 18 to 22 hours). Teddy bears are active at night, which lasts no more than two hours. As a rule, this is due to the need to find food for themselves.

It's funny that during the so-called periods of wakefulness, koalas practically do not move: they simply sit on the branches, holding onto the trunk with their forelimbs. At the same time, the koala sometimes shows enviable grace and lightness, deftly jumping from one tree (where all the food has been eaten) to another.

Nutrition

As scientists have found, such a leisurely lifestyle of koalas is not accidental. This is due to their diet. What do koalas eat? Why does nutrition have such an impact on their lifestyle? Knowing where koalas live, it is not difficult to answer these questions. The diet of these animals includes only eucalyptus leaves and shoots, which contain almost no protein. In addition, eucalyptus leaves are deadly for the vast majority of animals. This is due to the huge amount of phenolic compounds they contain.

Interestingly, not all eucalyptus trees are suitable for koalas. In addition, the animals are very selective in choosing leaves: they are good at recognizing the presence of hydrocyanic acid in them, which is dangerous to life. Moreover, animals are able to estimate its dose. In one night, an adult eats more than 500 g of young shoots and leaves. Special bacteria that develop in the intestines help cope with this volume of roughage plant feed.

It is thanks to the special environment that the leaves turn into a nutritious pulp and the proteins necessary for the body are produced. The processed food is stored in the cheek pouches, and to speed up digestion, the koala periodically swallows small pebbles and lumps of earth. Sitting on a peculiar diet of leaves saturated with essential oils, the koala is constantly in a state of mild intoxication, which can explain its “lethargy.”

Another interesting fact: given what koalas eat, it would be natural to assume that the animals drink a lot of liquid. However, this is not true: koalas practically do not drink water, except during particularly hot months. Animals have enough fluid, which they receive from plant food.

Security measures

Due to the fact that most of the traditional habitats of these animals were destroyed, only scattered populations have survived today. About a hundred years ago, koalas were on the verge of extinction. The people who were attracted by the soft and expensive fur of these animals were to blame for this. In 1924 alone, over two million koala skins were exported from Australia.

Today, koalas are under special protection; their extermination is prohibited. Koalas are bred in zoos and nature reserves, restoring their populations.

Reproduction

The decline in the number of animals is also explained by the low natural population growth. Almost 90% of females are infertile, and the rest reproduce slowly: they devote a lot of time to nursing the cub, which, as a rule, is the only one in the litter. Mating season begins in koalas in December and ends in March: for these months in southern hemisphere It is the end of spring or the beginning of summer. During this period, the dominant male in a certain area mates with females who are ready to breed offspring.

Mating occurs at night, high in a tree, and lasts about half an hour. At this time, partners bark, grumble loudly, scratch and bite. After the marriage sacrament is completed, the couple separates, and from that moment the male forgets about the offspring. After about 35 days, a tiny calf is born and is completely dependent on its mother. A blind and completely naked baby the size of a bean seed weighs no more than 3 grams. Its hind limbs are not yet formed at the time of birth, but its front legs with claws are already well developed.

Having been born, the baby crawls into the mother’s pouch along a path that the caring female licks in her fur, and for six months the baby does not leave the pouch, tightly attached to the mother’s nipple. In the first months, he feeds exclusively on mother's milk, but then the mother begins to feed the baby with a gruel of semi-digested leaves secreted with feces.

After six months, the cub comes out, climbs onto the mother’s back and travels with her through the trees. Up to eight months, he periodically hides in the pouch, but later he simply no longer fits in it: he has to stick his head into it to feed on his mother’s milk. From nine months old, the mature animal switches to its own bread. A one-year-old female acquires her own territory, and the young male is kicked out by his mother’s adult suitor during the next mating season.

We answered the main questions of people who are interested in these exotic animals: where does the koala live, what does it look like, how is its life organized. And now we want to introduce you to some interesting facts about these animals.

Koalas cannot be seen in European zoos, as in temperate climate Eucalyptus trees do not grow, and animals are in danger of starvation. Outside of Australia, they can only be seen at the San Diego Zoo, where a eucalyptus forest was planted especially for these animals.

My curiosity is unpredictable. Some people ask questions about the merits of the film “Australia”, some about the shortcomings, but I’m interested in why the koala (whose name is translated from the local language as “never drinking water") doesn't eat or drink anything except eucalyptus leaves? No, no, I understand everything about the niche, competition, evolution and all that. This is clear. I'm interested in something else - why can't he eat anything else? What is there in eucalyptus that no other plant has, that is irreplaceable for the koala, and without which this one of the most wonderful animals on the planet dies? There must be something firmly built into his metabolism. Or the koala does not have something that processes what is in all leaves except eucalyptus ones.

So, I went looking and along the way I learned a lot of interesting things about this eucalyptus.

Firstly, many of its species prefer to shed bark rather than leaves. Why is this tree called “shameless” in the vicinity of Tashkent? In Australia, for this habit, I suspect, they call it a stronger word, since during drought these light fibrous pieces catch fire at sight and are carried by the wind over a radius of up to 20 km. This reason for the neuroses of local firefighters accounts for up to 120 tons per hectare. No, there are individual conscious species that shed leaves, but there are only 10 of them out of more than 500 known. So you can imagine the quality of the fireworks.

And it’s impossible to keep up with these plant pyromaniacs. Do you feel like your children are growing up quickly? And then what do you think a eucalyptus mother should feel, who just yesterday dropped a tiny and cute seed, and a year later looking at an impudent teenager one and a half human height? By the age of five, a teenager will reach a height of 15 meters, and by the age of thirty he will turn into tree-like Valuev the size of a two-hundred-year-old oak tree. And he will cheekily look down on the tiny little people from the Forestry Institute in Canberra, jumping around and trying to get some seeds. To send a few fire-hazardous creatures overseas for breeding and forest planting, as a gesture of brotherly love and friendship between peoples. Not for free, of course. Well, the employees are no strangers either, they’ve been working for years and know how to earn money. Therefore, they cut off branches with fruits using shots from a rifle with an optical sight.

Everything else is cut by completely different people, armed with the best chainsaws that man has ever invented. Because more than one saw and broke more than one tooth on eucalyptus. What a tooth - wood-boring beetles lost their jaws at once. That’s why they don’t touch eucalyptus. The wood of eucalyptus trees is first-class, stronger than oak and black walnut wood, dense and heavy. In addition, it almost does not rot, and therefore is used for ship plating, piles, telegraph poles and supports for power lines.

Well, koalas don’t eat bark and wood, so I turned to leaves. And the eucalyptus leaf is like your VIP camera at the VIP entrance, into which the VIP security guard is looking at the VIP janitor who is sweeping the VIP yard, throwing over his shoulder “VIP yours just like that.”
The leaf blade on a long petiole is always rotated so that the plane of the leaf is parallel sun rays, then they slide along the sheet without stopping. Therefore, you don’t have to start looking for a shady corner in the eucalyptus forest to indulge in bliss and look at the koalas. Eucalyptus provides almost no shade.
For the same reason, leaves evaporate very little moisture. That’s why the koala receives its “ufologist’s diet” (well, it’s a completely ufological creature, you must agree), as befits an advanced space alien sent into difficult conditions - everything in one bottle, both water and food.

By the way, eucalyptus really absorbs water like a sponge. Thanks to its powerful root system, a hectare of eucalyptus forest sucks up to 12 million liters of water from the soil per year. For this reason, eucalyptus sponge is a very popular means of draining swamps. And that is why at one time mass plantings of eucalyptus trees began in the USSR, when it was necessary to drain the Colchis lowland.

Where there are leaves, there are flowers. A eucalyptus bud consists of two parts - a calyx and a cap. When the bud ripens, the cap falls off, and numerous multi-colored stamens burst out from the calyx in a riotous bunch. The flowers have practically no smell, although the eucalyptus itself smells great, we know that. What's the matter? Why such designer luxuries if a tree with the coloring “student of a closed Catholic school of strict security” grows out of them? And besides, the birds that pollinate eucalyptus trees are not good at perfumery delights. Their sense of smell is poorly developed, but their vision...compared to birds, we are all color blind. But some species of eucalyptus nevertheless acquired other helpers for their demographic needs - the marsupial opossum and flying foxes.

Yes, all this is very interesting, but what is so special about these leaves? And there, in special bags immersed in the leaf tissue, there is a large amount of essential oils- up to 5% of the weight of the leaves. Their composition varies depending on the type of eucalyptus, as does the aroma. Lemon eucalyptus smells...
Well, yes, it smells like lemons, what else. More than half of its essential oil is citral and citronellal, already familiar to us from “Chemical Charging”. Although this does not exhaust its aromatic range - additional colors are added by citronellol, which smells like roses, geraniol, isopulegone and some sesquiterpenes. That's why lemon eucalyptus is highly valued by perfumers. If Süskind's anti-hero had the opportunity to get acquainted with it, who knows, maybe he would have left his aunts alone. His attraction to thanatos could also be satisfied, since the young shoots of eucalyptus trees also smell of prussic acid.

But we all come across eucalyptus oils much earlier than we start using various odorous substances for a lot of money. Yes, yes, inhalations. The main suppliers of medicinal eucalyptus oil are. eucalyptus ball, ash and twig-shaped. Their oil contains up to 80% cineole. As soon as they smell the smell of this potent bactericidal substance, typhoid bacilli write a will, diphtheria bacilli pack their suitcases, and the dysentery amoeba crawls away with the words “sorry, I got the wrong door.” Even the famous carbolic acid does not produce such a deadly effect on these pests as eucalyptus oil. It is used for inhalation and as a good disinfectant and expectorant. Therefore, it is recommended for all sick people to plant eucalyptus in a tub, wait for it to germinate from the first to fifth floors and breathe the whole house with eucalyptus-enhanced air, the amount of essential oils in a cubic meter reaches up to 2.5 mg.

Yes, sir, but what about the koala, after all? Why can't he eat anything but eucalyptus? After all, other leaves also contain cellulose, the breakdown products of which it absorbs. So why? I was never able to find an answer to this question. Maybe some of you know him. But I think they're just really suited to each other - unique tree and a unique bear.

Quartl/Wikimedia Commons

Scientists have sequenced for the first time complete genome koalas and analyzed more than 26 thousand active genes, reported in 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 did they adapt to poisonous food, and how they differentiate suitable trees among the huge diversity of eucalyptus species, has until now been 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 different substances, turning them into water-soluble metabolites that are quickly excreted in the urine. It turned out that in koalas cytochromes are produced 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 bitter tastes - 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 by 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