Mainland animals are more aggressive and in command when threatened than their island relatives, says a study.
A team of researchers from various universities in the U.S. found that island lizards are indeed ‘tame’ as compared with mainland lizards.
The researchers were able to approach island lizards more closely than they could approach 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.
Darwin had noted that island animals often acted tame, and presumed that they had evolved to be so after coming to inhabit islands that lacked most predators.
“The suggestion by Darwin and others that prey on oceanic islands have diminished escape behaviour is supported for lizards, which are distributed widely on both continents and islands,” professor Garland added.
The research team also found that prey size is an important factor that affects escape behaviour, said the study published in the journal Proceedings of the Royal Society.
When prey are very small relative to predators, predators do not attack isolated individual prey. This results in the absence of fleeing or very short flight initiation distance, the study noted.
The researchers found no conclusive evidence showing that flight initiation distance is related to island area. They found, however, that predator approach speed is an important factor in lizards.
“It is possible that other factors favour island tameness. For example, if food is scarce on islands, the cost of leaving food to flee would favour shortened flight initiation distance,” professor Garland said.