March 30, 2009

Ecologists study lizard tail shedding

U.S. ecologists say they've identified the main factor that determines a lizard's ability to shed its tail when predators attack: viper venom.

University of Michigan scientists say tail-shedding is a common anti-predator defense among some lizards, with the ease with which they can shed their tails varying from species to species and place to place.

But the only predators that truly matter are vipers, said U-M Assistant Professor Johannes Foufopoulos, co-author of the study.

When non-venomous predators attack, tail-shedding is only useful in the relatively rare instances when the tail is firmly grasped by the predator, Foufopoulos said. But when a viper strikes, even glancing contact with the lizard's tail can inject a lethal dose of venom. In that case, the researchers said, the ability to shed a tail within seconds -- before venom reaches the lizard's vital organs -- is essential for survival.

The study that included the University of Michigan's Panagiotis Pafilis; Nikolaos Poulakakis of Yale University; Petros Lymberakis of the Natural History Museum of Crete and Efstratios Valakos of the University of Athens appeared in last week's online edition of the journal Evolution.