Island Living Makes Animals More Tame: Lizards Refuse to Flee (Video)

What makes animals "tame" and what makes them wild? You may have seen videos of the "tame" animals on the Galapagos Islands. Now, though, researchers have found evidence of this island tameness and have revealed that species that live on islands are more likely to demonstrate these attributes.

"Our study confirms Darwin's observations and numerous anecdotal reports of island tameness," said Theodor Garland, one of the researchers, in a news release. "His insights have once again proven to be correct, and remain an important source of inspiration for present-day biologists."

In order to examine island tameness, the researchers took a look at the relationships of flight initiation distance (the predator-prey distance when the prey starts to flee) to mainland, island area and occupations of an island. More specifically, they analyzed island and mainland lizard species from five continents and islands in the Atlantic and Pacific Oceans and the Caribbean and Mediterranean Seas. The researchers took into account differences in prey size and predator approach speed.

So what did the scientists find? It turns out that escape responses are reduced on remote islands since predators are either scarce or absent there. In addition, natural selection under reduced predation favors prey that do not waste time and energy developing and performing needless escape.

"The suggestion by Darwin and others that prey on oceanic islands have diminished escape behavior is supported for lizards, which are distributed widely on both continents and islands," said Garland in a news release.

That's not all the researchers found, either. They also discovered that prey size is an important factor that affects escape behavior.

"When prey are very small relative to predators, predators do not attack isolated individual prey," said Garland in a news release. "This results in the absence of fleeing or very short flight initiation distance."

The findings reveal why island tameness occurs and shows that it's largely due to the absence of predators-at least for lizards. This study confirms speculation and casual observation that has occurred for years.

The findings are published in the journal Proceedings of the Royal Society B: Biological Sciences.

Want to see some tame lizards? Check out the video below, courtesy of YouTube.