Jamaican lizards flex their muscles to greet new day

August 28th, 2008 - 12:15 pm ICT by IANS  

Washington, Aug 28 (IANS) Jamaican lizards greet each new day with vigorous push-ups and bobbing heads, unlike birds or primates that do it with chirping and tweeting.Terry J. Ord, postdoctoral researcher at Harvard University’s Museum of Comparative Zoology, said: “Anoles The lizards) are highly visual species, so in that sense it’s not surprising that they would use visual displays to mark territory.

“Still, the finding is surprising because these are the first animals known to use non-acoustic signalling at dawn and dusk.”

In a work that will appear in a forthcoming issue of the American Naturalist, 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 and push-ups, all to warn other males away from their territory.

Ord carefully located and videotaped individual males from 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.

“These patterns have remarkable parallels with the dawn and dusk choruses reported for many acoustically communicating animals,” he said.

As in many bird species, anoles leave their daytime perches at night to find safe shelter, since both birds and reptiles are frequently targeted by nocturnal predators.

“The dawn chorus may be a way of communicating having survived the night. If in the morning a bird doesn’t hear its neighbour, or an anole doesn’t see its neighbour, it may be an opportunity for the animal to expand its territory,” he added.

Ornithologists disagree on the exact reasons why birds chorus at dawn and dusk - competing hypotheses propose everything from territorial defence to favourable environmental conditions to manifestations of circadian rhythms. Ord said his work suggests male anoles use their morning displays primarily to mark territory.

“All of these behaviours are displays of physical vigour. As in humans, if an anole can do many of these push-ups it shows that he is in prime physical condition. These displays of strength help avert actual physical confrontations between male lizards, which can be very fierce and destructive.”

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