Adaptation to climate | Australia
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And Australia continued moving north on its slow journey across the Indian Ocean.
The closer it came to the Tropic of Capricorn, the more temperate the climate became. Where once there had been jungle, vast open plains appeared The pasture took over the land, and new colonists appeared, some of them close relatives of those who still now live hidden in the last remaining jungles of Australia.
The emu is a close relative of the cassowary, but because it has been able to adapt to the plains, it has spread over a much larger area of Australia. When the breeding season arrives, the males do almost all the work. In a protected spot, from which the surrounding area can be observed, the male prepares a simple nest. .
The open plains were a new testing ground for the animals of Australia. To survive here, it was necessary not only to be able to withstand seasonal droughts, and feed on grasses, but also to be able to flee from enemies at great speed. With their powerful legs, the emus can run at fifty kilometres an hour. But how did the marsupials manage?
Away from the protective cover of the forest, there were no trees in seek refuge, and the main food source was pasture. And, nonetheless, the plains were to be the place where the most emblematic animals of the entire continent would evolve – the kangaroos.
Wallabies, pademelons, wallaroos and kangaroos themselves developed a dentition and a digestive system which enabled them to feed on the tough grasses. Out on the plains, they were more exposed, especially in the breeding season, but the very fact they are marsupials proved to be a great advantage.
When they had to take flight, they simply put their young in the pouch, and fled at great speed. The marsupial’s pouch replaced the protective jungles for these young and inexpert kangaroos. There, they had shelter, protection and food.
But the adaptations of the kangaroos did not stop there. The development of a powerful tail provided stability, which meant they were able to stand up on two legs, and remain erect, above the grasses, scanning the vast horizon. The tail was also the final touch in the most important adaptive weapon of all – powerful legs which enabled it to flee at great speed, and what’s more, do so by jumping, and so avoiding the obstacles of the landscape.
A quoll, a carnivorous marsupial, which the colonists named the ‘native cat’, in order to distinguish it from the domestic cats they brought with them in their ships.
Like the real cats, the quolls are expert hunters, and the Australian night is full of potential prey.
Insects are an important part of the diet of this small, silent nocturnal hunter, so the formation of open land was to their advantage. The flowers attracted insects, and hunting became easier. But, approximately fifteen million years ago, when the continent of Australia came close enough to the islands of what is now Indonesia, some rodents managed to reach the coast, and immediately became highly-valued prey for the native hunters.
In the ancestral competition among the different groups of mammals, this was a victory for the marsupials. Twenty million years of isolation meant they were the best equipped to dominate their territories, and these small eutherian mammals, far from posing a threat, became an important part of their diet.
In the distant days of the fragmentation of Gondwana, Australia was inhabited by large marsupials. Some of them were herbivores – some the size of present-day hippopotamuses – and others vicious hunters, similar to today’s lions and tigers. But the fight between hunters and prey in present day Australia is on a somewhat more modest scale.
On the soft ground, covered in leaves, a bandicoot is looking for worms and insects, hidden in the shadows. The same leaves that hide tasty mouthfuls, also serve to cover its tunnels, in which it takes refuge when danger appears. Because, though they may look cute, some of the nocturnal marsupials are, in fact, fierce hunters.
The brush-tailed phascogale is not the cheeky squirrel it appears to be. The first colonists in Sydney baptised it the vampire marsupial, and spoke of it as a ‘bloodthirsty killer’. And perhaps it is, for the cockroaches, beetles and spiders which make up the main part of its diet. Because the evident exaggeration of the colonists is due more to the character of the phascogale than to the raids which, from time to time, it makes on the hen houses, where it kills and devours the birds.
The union of marsupials and rodents made new adaptations necessary. Both groups competed for the same resources, and in this battle, new and original means of survival appeared.
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