the American Acclimatization Society—one of dozens of perfectly legal groups dedicated to spreading species around the world
Others were too successful. Australia was a popular places to send European species, largely because the settlers there were suspicious of the native flora and fauna and wanted to see some more familiar animals (“The swans were black, the eagles white… some mammals had pockets, others laid eggs… and even the blackberries were red,” complained one, named J. Martin, of his time there).
Members of Society there brought in blackbirds, thrushes, partridges, and rabbits, the latter of which soon overran the continent. The same thing happened with opossums in New Zealand. To fix this problem, they tried bringing in weasels and stoats, which began eating birds instead of the intended target. Both countries are still dealing with the devastation caused by these decisions.