Lucky Lizards: Lack Of Predators Makes Island Animals Tamer

By Rhonda J. Miller on January 12, 2014 8:24 PM EST

Iguana In California May Not Be As Tame Island Lizards
An adult desert iguana photographed near Palm Springs, Calif. may not be as tame as lizards living on the Galapagos and other islands. A new study confirmed Charles Darwin's theory that island animals are more tame than their mainland cousins. (Photo: Theodore Garland, UC Riverside / Rhonda J. Miller)

Island living may conjure up a vision of the ultimate relaxation for humans — just kicking back surrounded by the sea, the sand, the sun, and usually getting a respite — at least temporarily - from frustrating traffic jams and endless obligations.

Now scientists have found that island living has an evolutionary effect on lizards: They tend to be tamer than their mainland cousins. A team of researchers gave a nod to Charles Darwin's theories of more than 150 years ago that the "tame" animals of his beloved Galapagos Islands became better suited over time to their environment because they had relatively few predators, according to phys.org

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

The findings of the study, "Island Tameness: Living On Islands Reduces Flight Initiation Distance," went online Jan. 8 in the Proceedings of the Royal Society B, a biological sciences research journal, and will be in the February 2014 print edition. 

The researchers studied 66 species of lizards, taking into account differences in the size of the prey and the speed of the approaching predator. The study expanded the examination of tame island animals more broadly than Darwin's Galapagos Islands theory, widely examining lizards from five continents and islands in the Atlantic and Pacific Oceans, and the Caribbean and Mediterranean Seas.

The team measured "flight initiation distance,"  which is when the prey begins to flee, in comparison with mainland relatives.  The scientists found that distance is shorter in island lizards and that distance is also shorter the farther away the animals are from the mainland. "Our results demonstrate that island tameness is a real phenomenon in lizards," the researchers said in a study abstract.

The renowned naturalist Charles Darwin theorized about the tameness of animals on Galapagos Islands as an offshoot of his theories of evolution related to natural selection, the Daily Mail reported. Darwin sailed on the HMS Beagle 183 years ago to the Galapagos off the coast of Ecuador, where he began to suspect the tameness of animals resulted from the absence of predators.

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