January 11, 2014
Island Living Makes Animals Tamer
[ Watch the Video: Island Animals Are Tamer Than On The Mainland ]
Lee Rannals for redOrbit.com - Your Universe OnlineLike Hawaiian vacationers, living on an island actually makes animals tamer, according to a study published in Proceedings of the Royal Society B.
Charles Darwin, the founder of the theory of evolution, used the Galapagos Islands as his laboratory when studying animals. The Galapagos is where Darwin developed his ideas about natural selection and how organisms evolve genetically across generations. He also wrote about how island animals often acted tame and presumed they evolved to be this way after coming to inhabit islands that lacked predators.
Researchers from the University of California, Riverside, Indiana University, Purdue University Fort Wayne and George Washington University have confirmed that these island dwellers are indeed “tame” when compared to their mainland relatives.
"Our study confirms Darwin's observations and numerous anecdotal reports of island tameness," Theodore Garland, a professor of biology at UC Riverside and one of the paper's coauthors, said in a statement. "His insights have once again proven to be correct, and remain an important source of inspiration for present-day biologists."
The team looked at the "relationships of flight initiation distance (the predator–prey 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 also analyzed island and mainland species from five continents and islands in the Atlantic and Pacific Oceans and the Caribbean and Mediterranean Seas.
The researchers discovered that island tameness exists and that flight initiation distance shrinks the farther out the island is from 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.
The researcher added that escape responses are reduced on those far-away islands because predators are more scarce, or are even absent, there. This means that natural selection under reduced predation favors prey, making islands the true paradise for animals like lizards. Because these paradises lack predators, lizards have evolved in a way that does not waste time and energy developing and performing escapes.
"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."
While no evidence was found for flight initiation distance being related to island tameness, the researchers did discover that predator approach speed is an important factor. Garland said it is possible that other factors could favor this island tameness observed as well.
“For example, if food is scarce on islands, the cost of leaving food to flee would favor shortened flight initiation distance," the researcher said in the statement.