Lizards Evolving Rapidly to Survive Deadly Fire Ants

January 21, 2009

Long legs and skittish behavior are recently evolved traits that allow fence lizards in the southeastern U.S. to co-exist with lethal and invasive fire ants, according to a new study.

The new findings could boost hopes for species whose habitats are quickly changing due to climate change, experts say.

The venom-packed stings of just 12 fire ants can kill a three-inch-long (eight-centimeter-long) fence lizard in a minute, according to lead study author Tracy Langkilde, a biologist at Pennsylvania State University. The ants have been known to strip animals as large as calves down to the bone.

But some lizards twitch vigorously and flee the scene whenever ants attack, a defensive behavior that sheds the insects before they can pry up the reptiles' scales and sting the soft flesh underneath.

The findings, Langkilde said, are evidence of a rapid evolutionary response to the fire ants.

(See more photos of evolution in action.)

Survival of the Fittest

Fire ants were accidentally introduced to the U.S. from South America in the 1930s, possibly via shipping ports in Alabama.

Without a method for controlling the population, scientists believe fire ants—which have no natural predators, in the U.S.—will eventually colonize more than 50 percent of Earth's land surface.

(See related: "USDA Fights Invasive Fire Ant With Flies" [December 21, 2005].)

Longer hind limbs appear to help the lizards twitch and flee more effectively, said Langkilde, who received funding for her study from the National Geographic Society's Committee for Research and Exploration. (The National Geographic Society owns National Geographic News.)

Langkilde studied adult lizards from four populations and found that extended limbs and skittish tendencies were increasingly more common at sites where lizards and fire ants had co-existed longer.

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