Study results appear online this week in the Proceedings of the Royal Society B. They will appear in the journal in print on Feb. 22.
The researchers conducted analyses of relationships of flight initiation distance (the predatorprey distance when the prey starts to flee) to distance to mainland, island area, and occupation of an island for 66 lizard species, taking into account differences in prey size and predator approach speed. They analyzed island and mainland lizard species from five continents and islands in the Atlantic and Pacific Oceans and the Caribbean and Mediterranean Seas.
Their results showed that island tameness exists and that flight initiation distance decreases as distance from mainland increases. In other words, island lizards were more accessible the farther the islands were from the mainland.
"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," Garland said.
He explained that escape responses are reduced on remote islands, because predators are scarce or absent there, and natural selection under reduced predation favors prey that do not waste time and energy developing and performing needless escape.
The research team also found 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," Garland said. "This results in the absence of fleeing or very short flight initiation distance."
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.
|Contact: Iqbal Pittalwala|
University of California - Riverside