Mates Play Charade in Lizard Love

NEW YORK -- A complicated mating game is going on in California, played by harem-keeping males, female impersonators and fellas who just want to get along.

They're all lizards -- literally.

Scientists studying the side-blotched lizard in rocky outcrops in the foothills of the Coast Range report that the male mating strategies resemble the child's game of rock-paper-scissors.

In that game, children simultaneously choose to present an imaginary rock, paper or scissors. Rock beats scissors, scissors beats paper and paper beats rock. So each object beats one object but loses to another.

So it is with three kinds of mating strategies in the male lizards, Barry Sinervo and Curt Lively of Indiana University in Bloomington reported in Thursday's issue of the journal Nature. They showed that, over a six-year period, the mating strategy that got the most females constantly shifted, with each being most effective when it was least common and least effective when most common.

"This is the first biological example we know of the rock-paper-scissors game," Sinervo said.

The mating game is played by males with one of three color markings on their throats. Males with orange throat markings are very aggressive and defend large territories, keeping harems of up to six females. They take females away from the blue-throated male, which is less aggressive and typically has only one or two females.

When the orange-throats are common, it's a bonanza for the third kind of male, female impersonators with yellow- striped throats. These "sneakers" invade orange-throat harems for quick sex, avoiding harm because they look and behave like females. "The oranges just fall for the charade," Sinervo said.

If the sneakers are successful enough to have lots of offspring, the males of which tend to be yellow-throated, then in a generation or two there will be more that tend to be yellow-throats in a population and far fewer orange-throats.

That opens the door for the blue-throats. Though they don't challenge the more aggressive orange-throats, they can easily run off the yellow-throated sneakers. They're not fooled by the sneakers' female impersonation.

So then the blue-throats have their day, because they can set up territories and defend females against the sneakers without having to worry about a lot of orange-throats around.

But in a couple of generations, the burgeoning population of blue-throats means more females are being guarded by them, opening up an opportunity for the aggressive orange-throats. Then the orange-throats begin to win away more females, starting the cycle all over again.