Washington, August 28 : A new study has revealed that a Jamaican lizard called the Anolis engages in impressive displays of reptilian strength - push ups, head bobs, and threatening extension of a colourful neck flap called a dewlap - to defend its territory at dawn and dusk.
"Anoles 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," says Terry J. Ord, a postdoctoral researcher at Harvard University's Museum of Comparative Zoology and at the University of California, Davis.
A research article in the journal American Naturalist reveals that Ord studied four species of Jamaican forest lizard, namely Anolis lineatopus, Anolis sagrei, Anolis grahami, and Anolis opalinus.
While female anoles establish small territories allowing access to food and other resources, while males stake out larger territories allowing them access to several females.
Ord has observed that male anoles spend much of the day sitting on tree trunks, displaying head motions, push-ups, and dewlap extensions, in order to warn other males away from their territory.
Filming individual males at different times of day, from before dawn to dusk, he found that 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," Ord says.
He has also found that like many species of birds, anoles leave their daytime perches at night to find safe shelter because 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," Ord says.
While ornithologists disagree on the exact reasons why birds chorus at dawn and dusk, Ord says that his work suggests male anoles use their morning displays primarily to mark territory.
"All of these behaviors are displays of physical vigor. 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," Ord says.
His work may open the doors to further study by ornithologists, herpetologists, and others seeking evidence of non-acoustic dawn and dusk signalling among other species.