When Darwin explored Saint Paul's Rocks off the coast of Brazil, he found just two kinds of birds. He wrote: "Both are of a tame and stupid disposition...I could have killed any number of them with my geological hammer." Darwin's hunch was that creatures living on remote islands were less wary of predators--because in many cases, there weren't any.
And it seems he was right. Because by analyzing dozens of past studies, researchers have found that island lizards are indeed less skittish than their mainland relatives. That finding appears in the Proceedings of the Royal Society B. [William E. Cooper, Jr., R. Alexander Pyron and Theodore Garland, Jr., Island tameness: living on islands reduces flight initiation distance]
Problem is, that mellow island lifestyle could endanger the lizards, if invasive predators show up. "The lizards in the islands will be a lot more vulnerable.” That’s evolutionary biologist Theodore Garland, Jr,, a member of the study research team. “They will allow those new predators to approach to a closer distance, which is going to probably greatly increase the chance that they'll actually be captured by an introduced predator." Which suggests that, compared to mainlanders, island fauna don't stand a fighting chance—unless we keep invasive predators at bay.
[The above text is a transcript of this podcast.]