Twenty-four rabbits set lose in Australia grew to a population of 10 billion in about 67 years.
In 1859, a man named Thomas Austin in Barwon Park, Australia released 24 rabbits. These European wild rabbits spread rapidly, about 130 km per year. By 1926, there were over 10 billion rabbits in the island.
Since the peak in population, disease has reduced the rabbit population down from billions to hundreds of millions. Rabbits reproduce at a ridiculously fast rate. Rabbits are mature enough to reproduce after only three or four months of life.
After that, they have a very short gestation period of only 28-30 days. A female rabbit creates a burrow to breed in. A female rabbit can birth 5-6 litters a year, with about 5 baby rabbits in each litter. That means a single female rabbit could give birth to as many as 30 new rabbits in a year.
These rabbits are very hazardous to the ecosystem of Australia. Rabbits feed on certain plants in particular, so those plants got eaten up by the high population of non-native rabbits.
The absence of those plants affected other native animals in the area. This changed the ecological landscape of Australia. Rabbits also hurt the economy by overgrazing in farm areas.