An island, on the other hand, is small. There are fewer species, and the competition for survival has never reached anything like the pitch that it does on the mainland. Species are only as tough as they need to be, life is much quieter and more settled [..] So you can imagine what happens when a mainland species gets introduced to an island. It would be like introducing Al Capone, Genghis Khan and Rupert Murdoch into the Isle of Wight - the locals wouldn't stand a chance.