As Charles Darwin learned several centuries ago, islands are havens for evolution. Newcomers to these isolated worlds find themselves unshackled from the predators that dogged them on the mainland. They celebrate their freedom by diversifying into a great variety of species. But predators still have ways of tracking them down, and following the footsteps of sailors is one of them. By killing adults and eating eggs, introduced predators such as rats, cats and stoats are responsible for nine in ten of the bird extinctions since 1600.
Now, conservation agencies are getting serious about introduced predators. As an example, they have spent increasingly large budgets in recent years on the eradication of rats from troubled islands. Smaller stowaways like mice typically escape the conservationists' wrath, and between 2001 and 2005, twenty-five times less money was spent on dealing with them. After all, mice are smaller and less opportunistic than rats and ...
