Why are there no rabbits in Australia?

Rabbits were not originally produced in Australia. /kloc-in 0/859, twelve European rabbits were brought to Australia from England by immigrants. These rabbits found themselves in heaven: there were no natural enemies such as eagles and foxes in Australia, and kangaroos in the same small ecology could not compete with them, so these rabbits began to breed in large numbers with almost no restrictions. By 1886, the offspring of these rabbits began in the southeast of Australia and spread in all directions at an average rate of 66 miles per year. By 1907, rabbits had spread to the east and west of Australia, covering the whole continent. As rabbits compete with sheep and cattle for pasture, Australia's animal husbandry has suffered huge losses. Australians try their best to limit the spread and reproduction of rabbits, build fences, hunt, catch and poison them. Methods have been exhausted, but the rabbit disaster can't be eliminated.

In 1950s, the Australian government decided to use biological control to eliminate rabbit plague. Biologists introduced a virus spread by mosquitoes from America. The natural host of this virus is an American rabbit, and this virus produces myxoma in American rabbits, which is not fatal. But they are fatal to European rabbits and completely harmless to people, livestock and wildlife in Australia. They are undoubtedly the most ideal weapons to destroy Australian rabbits. Sure enough, by 1952, a nationwide plague broke out in Australia, with a mortality rate as high as 99.9%. It seems that the extinction of rabbits in Australia is just around the corner.

However, an evolutionist can completely predict what will happen next: natural selection is at work. On the one hand, rabbits choose viruses: there are various variants of the same virus, some of which are more toxic and some are less toxic; Because viruses have to rely on the host to survive and reproduce, those highly toxic viruses die with the death of their parasitic rabbits, while those less toxic viruses survive. On the other hand, the virus also chose rabbits: rabbits with poor resistance were eliminated first, and rabbits with strong resistance survived. After generations of selection, their offspring become more and more resistant. As a result of mutual selection, there are weak viruses and resistant rabbits, which will eventually lead to a rebound in the number of rabbits.

This is exactly the case: the number of rabbits is increasing year by year, and the mortality rate is getting lower and lower, and now it has dropped to 40%. Although myxomatous plague still breaks out among rabbits in Australia every year, it is not so effective in controlling the number of rabbits. This is exactly what evolution is at work, triggered by humans and observed by humans. There is no other theory to explain this phenomenon except evolution. Now, Australian biologists are developing a more virulent myxoma virus to increase the mortality rate of rabbits. Obviously, this will lead to another round of choices and history will repeat itself.