In Australia, 24 European rabbits were released, starting one of the fastest colonizations in history. They were commissioned by colono Thomas Austin for the hunting sport. Without counterbalance, this species spread 100 kilometres a year westward, becoming an uncontrollable pest for flora and fauna. It was the fastest colonization ever done by a mammal species, and for 50 years it spread across the island. It is taken as an example of factors that can lead a system to collapse.