Charles Darwin's Galapagos theory that living on islands makes animals tamer than their mainland counterparts, has now been proved scientifically in a new study.

Researching on the 56 different species of lizards, researchers from the University of California, Riverside, Indiana University, Purdue University, Fort Wayne and George Washington University found that those living on islands were tamer than those living in the mainland.

Researchers observed that, the island lizards were more closely approachable compared to mainland lizards.

"Our study confirms Charles Darwin's observations and numerous anecdotal reports of island tameness. His insights have once again proven to be correct, and remain an important source of inspiration for present-day biologists," said Theodore Garland, professor of biology at University of California, Riverside.

183 years ago, in his theory, Darwin had noted that island animals often presumed they had evolved to act tame as the place lacked most predators.

"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," professor Garland added.

Researchers also found that the size of the prey played an important factor that affected escape behavior as most of the predators did not attack small and isolated prey.

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

No concrete evidence was found in the study that could prove the relation between flight initiation distance - the point at which prey flees from a predator, and island area. However the findings suggested that the predator speed is an important factor in lizards living at mainland and islands.

The study has been published in the journal Proceedings of the Royal Society.