Forty five million years ago Australia When the continent separates from the Antarctic plate and gradually drifts northward, koala or similar Koala Our animals have already started to evolve. Fossils prove that animals like koalas existed on the Australian mainland 25 million years ago. In the process of drift, the climate began to change dramatically, and the Australian mainland became drier and drier. Eucalyptus Rubber tree Other plants also began to change and evolve, and koalas began to become dependent on these plants. It is generally believed that aborigines came to the Australian mainland 60000 years ago or even earlier. Like other Australian animals, koalas have also become an important part of many myths and legends in indigenous culture and civilization.
For thousands of years, koalas have been an important source of food for indigenous people, but this does not hinder their prosperity. In 1788, after Europeans first landed on the Australian mainland, John Price became the first European to record the koala. He described koala in detail when he entered Blue Mountains near Sydney. In 1816, koalas first got the scientific name "phascolarctos cinereus", which means "grey wombat". Later, people found that koalas were not bears at all, so members of a mammal research group called them "marsupials" (meaning“ Marsupials ”）That is, the newborn animals are not fully developed and need to continue to develop in the pouch. Most marsupials, such as koalas, are found in Australia and Papua New Guinea. In Australian aboriginal languages, koala means "no water", although Australian dialects are diverse. In different versions of colonial materials, koalas were recorded in many different formats, such as cullewine, koolewong, colo, colah, koolah, kaola, koala, karbor, boorabee, And goribun, etc.
When new settlers entered the Australian mainland, deforestation and reclamation began, and the native animals in Australia began to lose their habitat. In 1924, koalas were extinct in southern Australia, new south wales The number of koalas in Victoria is estimated to be less than 500. As a result, the transaction focus of koala fur began to turn north to Queensland. In 1919, the Australian government announced a six-month hunting ban lifting period, during which 100 million koalas were killed. Although the special season for hunting koalas was officially cancelled in 1927, when the ban was cancelled again, more than 800000 koalas were killed in just over a month. In 1930, the brutal public hunting of koalas forced the government to declare that koalas became protected animals in all states. However, except for the relevant laws promulgated by New South Wales, there is no law to protect those koalas who rely on survival and concealment eucalyptus Forest. 
Quadruped koala The earliest quadrupeds appeared in the late days about 370 million to 350 million years ago Devonian , which still retain certain fish characteristics Amphibian It is important to explore the origin of quadrupeds value It provides the most abundant and direct information to understand how our ancestors climbed out of the primitive swamp and came to live on land. The emergence of quadrupeds, vertebrate The landing of. Because of this biological event, modern Terrestrial ecosystem Only when the rudiments of the human race began to take shape, did the earth have giant animals - dinosaurs, birds and animals, and human beings themselves. The quadruped characteristics of koalas
Like quadruped koalas, they are very suitable for arboreal life. Although unlike other arboreal marsupials such as the tree kangaroo, the koala has no obvious tail, this does not affect its excellent sense of balance; The koala has well-developed muscles, long and strong limbs, and is suitable for climbing among branches and supporting its weight. Forelegs are almost the same length as legs, to climb The strength mainly comes from the developed thigh muscles. Koalas' claws are particularly suitable for grasping objects and climbing. Rough palm pads and toe pads can help koalas cling to branches, and their limbs have sharp long claws. The forefoot has five fingers, two of which are opposite to the other three fingers, just like the human thumb, so it can be held against other fingers, which enables the koala to grip objects more safely and confidently. On the sole of the foot, except that the big toe has no long claws, other toes have sharp long claws, and the second toe is connected with the third toe.
When approaching the tree to climb, the koala jumps up from the ground, grabs the bark with its front paws, and then jumps up to climb. Therefore, when a tree becomes the family tree of koalas and is often climbed, the scratches left by koalas' claws on the bark are very obvious. Another sign that proves a tree is used by koalas is that there will be koalas' small globular feces at the base of the tree.
Whether in the day or at night, when the koala is in a safe home tree, it will naturally show a variety of different sitting and sleeping positions. At the same time, it will also keep moving in the tree because it avoids the sun or enjoys the breeze. When the weather is hot, koalas will spread out their limbs and swing slightly to keep cool, while when the weather is cold, they will shrink their bodies into a ball to keep warm.
The koala descends the tree in a downward position. Koalas often go down to the ground and climb to another tree. At this time, they are often attacked by domestic dogs, foxes, Australian wild dogs, or killed or injured by passing vehicles. Koalas can swim, but only occasionally.
Koalas have thick fur, which is good for keeping their temperature constant. In addition, they can also be used as raincoats when it rains, so as to avoid moisture and rain. The fur of koalas presents various colors from light gray to brown, among which there are white patches on the chest, neck, limbs and inside of ears. Adult male koalas have a particularly striking brown scent gland in the center of their white chest.
Koala The tail fur is particularly thick, because koalas often use it as a cushion, and it is often polluted, so that when koalas go down to the ground with their buttocks facing you, it will be difficult to find its existence. Adult male koalas usually weigh 8-14kg, while female koalas weigh 6-11kg. They are distributed in the south and have larger weight and thicker fur because they need to adapt to the colder climate.
Koalas generally belong to Nocturnal animal The activity is vigorous at night and in the morning and evening, because it can save water and energy consumption more than the activity in the day when the temperature is higher. Koalas spend an average of 18-22 hours a day sleeping and resting, and only the remaining 4 hours are used for food gathering, activities, personal hygiene and communication with other koalas. In the past, because koalas slept almost all day, people thought that koalas were poisoned by eating eucalyptus leaves. Koalas are sleepy almost all day long, which is actually an effective low metabolism adaptation mechanism formed in their long-term evolution process to adapt to low nutrition food and save energy consumption. The most obvious feature of koalas is their well-developed nose, which enables them to have a highly developed sense of smell. They can easily distinguish different kinds of eucalyptus leaves, and find out which ones can be eaten and which ones are poisonous and cannot be eaten. Of course, it can also smell the warning smell left by other koalas.
Koalas can make a variety of sounds to contact and communicate with other koalas. Male koalas mainly indicate their dominance and dominance by roaring, so as to avoid energy consumption in fighting and show their position to other animals.
Female koalas do not roar as often as male koalas do, but they may not. For example, when mating, female koalas will make a sharp scream, giving the impression that they are fighting with each other. The female koala and the young koala will also make soft ticking, whistling, mild buzzing and grunting sounds, while the mild grunting sounds show dissatisfaction with each other. However, when the koala is afraid, it will make a sound similar to a baby crying, accompanied by trembling and shaking. Koalas also mark trees with the scent produced by their glands.
