Behind the Scenes: Lizard Love Triangles

Here you thought only humans snuck around on each other. We have nothing on these prehistoric creatures, the sneaky little reptiles.

Lizard Love Triangles Exposed

A three-way sex struggle resembling the game rock-paper-scissors may have existed for 175 million years or more in lizards, research now suggests.

The reptilian triads may be far more common than previously recognized—and may even shape the way humans behave, the scientists said

"You either cooperate, or take by force, or take by deception," said researcher Barry Sinervo, a behavioral geneticist at the University of California, Santa Cruz. "It's one of those basic games that structures life."

Color-coded

The scientists investigated European common lizards (Lacerta vivipara), devoting five years to studying the lizards at five sites in the Pyrenees mountain range on the border of France and Spain. They captured more than 250 lizards per year and followed their successes and failures.

Sinervo and his colleagues found males adopt one of those three strategies when pursuing females. A quick look at their gaudy-colored bellies reveals which line of attack they will pursue.

Orange-bellied males are brutes that invade other lizards' territories to mate with any female they can hold. But while they're gone, yellow-bellied males sneak deceptively onto the vacant territory and mate with undefended females. White-bellied males guard their mates closely and ally with other white-bellied lizards to keep the yellows at bay. Thus the analogy to rock-paper-scissors—orange force defeats white cooperation, cooperation defeats yellow deception and deception defeats force.

The researchers predicted this species would play the modified rock-paper-scissors game due to a high population density, "which allows a despotic type to flourish, which sets up conditions for cheaters, which in turn sets up conditions for cooperators to invade," Sinervo told LiveScience.

In practice, this game of sex leads to a steady cycling of which lizard color type is prevalent every four to eight years. For instance, orange aggressors may be dominant for a year or two, followed by yellow deceivers, succeeded by white cooperators and then back to orange as the cycle starts anew.

Scientists first conjectured that evolution would conjure up such rock-paper-scissors games in 1968, but they were not actually discovered in nature until 1996, when Sinervo uncovered an example in side-blotched lizards (Uta stansburiana), which are among the most abundant lizards in the arid western United States.

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