I'll Show You Mine if You Show Me Yours

If an angry lizard opens its mouth in your direction, you better pay attention. A new study reveals that other lizards can tell how hard the attacker can bite from a quick examination of its jaw muscles.

When an adult male lizard opens his jaws at a rival male during a heated territorial battle, the opponent can take a peek at the lizard's clearly visible jaw muscles to estimate how hard he can bite. Some species, such as the collared lizard pictured here, have evolved bright colorations that reflect ultraviolet light, which lizards can see and delineates the muscles even more.

When two competitors engage in a gaping display, each shows off its weapon while simultaneously checking out what the other guy has. By broadcasting this unique and honest information about weapon quality, and having the ability to make the decision to fight or back down, fights can be avoided.

"When you've seen what these lizards can do to each other with their jaws, inflicting deep lacerations and even breaking bones, it makes sense that avoiding fights would be advantageous, even if you are likely to win," said study co-author Krisopher Lappin of Northern Arizona University.

This type of weapon-rating behavior is displayed in many animals, including humans, where posturing and showing off on the playground established dominance.

The study was detailed in the July issue of The American Naturalist.