2008-08-29 08:14:46 - Like the ageless fitness guru, the lizards greet each new day with vigorous push-ups. That's according to a new study showing that male Anolis lizards engage in impressive displays of reptilian strength -- push-ups, head bobs, and threatening extension of a colorful neck flap called a dewlap -- to defend their territory at dawn and dusk.

The lizards are the first animals known to mark dawn and dusk through visual displays, rather than the much better known chirping, tweeting, and other sounding off by birds, frogs, geckos, and primates.

Terry J. Ord, a postdoctoral researcher at Harvard University's Museum of Comparative Zoology and at the University of California, Davis, describes the Anolis lizards' unusual morning ritual in

a forthcoming issue of the journal American Naturalist.

"Anoles are highly visual species, so in that sense it's not surprising that they would use visual displays to mark territory," Ord says. "Still, the finding is surprising because these are the first animals known to use non-acoustic signaling at dawn and dusk."

Ord studied four species of Jamaican forest lizard: Anolis lineatopus, Anolis sagrei, Anolis grahami, and Anolis opalinus. Female anoles establish small territories allowing access to food and other resources, while males stake out larger territories allowing them access to several females. The males spend much of the day sitting on tree trunks and displaying head motions, push-ups, and dewlap extensions, all to warn other males away from their territory.

Ord carefully located and videotaped individual males at different times of day, from before dawn to dusk. In all four species, he found distinct peaks of activity at daybreak and for about two hours afterward, and again just before dark.

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