Take for example the Small Indian Mongoose – introduced to many islands such as Mauritius, Fiji and Hawai'i from its native southern Asia to help control rats. Many local species – birds, reptiles, amphibians – were not used to such a fast moving predator. It wasn't long before they could no longer be found on the islands. They became what scientists call "locally extinct".
Or how about the Rosy wolfsnail – introduced to control another invasive species (the giant African snail – which was meant to provide a new source of food, but went rampant). The Rosy wolfsnail was so good at its job that it went to on to "control" all the other species of snails as well. The impacts have been profound with Rosy wolfsnail chalking up several extinctions to its name.
Or the Nile perch. Introduced to Lake Victoria in Africa in 1954 to counteract the drastic drop in native fish stocks caused by over-fishing (there we go with that over-fishing again…). Yet the Perch's introduction contributed to the extinction of more than 200 local fish species through predation and competition for food.
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