In a demonstration of reptilian strength, Jamaican anole lizards begin and end each day with a visual display that includes push-ups, head bobs and flashy showings of their colorful neck flaps, according to a new study.
The lizards are now the first animals known to mark dawn and dusk with a visual routine, instead of the more typical noisy critter shows that involve hoots, chirps, tweets and other sounds.
"Up until this study, dawn and dusk choruses have only been documented for acoustic signals," Terry Ord, who conducted the study, told Discovery News.
Ord, a postdoctoral researcher at the University of California at Davis and at Harvard University's Museum of Comparative Zoology, explained that birds, frogs, geckos, primates and other animals sound off at such hours, but the Jamaican anole lizard proves that "the same phenomenon occurs for visual signals."
He studied four different species of Anolis lizards at various sites on the island of Jamaica. Adult males were the primary focus of his research, since previous studies had found that the lizards' mating system relies on males establishing and defending territories.
When he spotted a lizard, Ord would set up a camcorder near the reptile's perch to record its behavior. The findings are published in the October issue of American Naturalist.
Both females and males were observed performing calisthenic-like displays, but the males "exercised" more frequently and with greater predictability. Many females also lack the colorful neck flap, technically called a dewlap.
Each species was found to have its own unique routine, with some performing "rapid head bobs that end with several rapid flashes of the dewlap" and others starting off with "several extensions of the dewlap, then performing a dozen or so head bobs that are longer in duration."
Male and female lizards, along with predators, may view the morning and evening shows, but Ord thinks they are performed mostly for the sake of other watchful males.
"The visual displays are meant to advertise to other neighboring males that they still occupy their territory," Ord explained. "If a male leaves the area too long, another male will probably try to take his territory over."
He said that it's better for the lizards to expend energy displaying their strength and endurance than to put the skills to test in actual combat.
"Instead of finding this (information) out in the middle of a fight — which is a really bad time to find out your opponent is a lot stronger than you — they can advertise...in their displays and resolve disputes without resorting to fighting at all," Ord said.
Judy Stamps, a professor in the Department of Ecology and Evolution at UC Davis, told Discovery News that she "was delighted to see this article, because it confirms a vague impression I had years ago when watching lizards in the West Indies, that territorial males were most likely to display the first thing in the morning, and the last thing at night."
She agrees with Ord's theories behind the dawn and dusk displays, and added that the lizards might also choose such hours "because these times of day are less favorable for other important activities, such as foraging, or chatting up the females."