Laborin' lizards

Anolis sagrei in Jamaica

Courtesy of Luke Mahler / Harvard University

Head bobs, a series of quick pushups, and displays of a colorful double-chin. Life as a male anole lizard defending its territory against other male lizards is a lot of work. As is the life of the single-minded scientist who chooses to study them.

"Most of the time I work alone because it's a lot to ask for assistants to spend hours on their feet following lizards around all day," says Terry Ord, who is completing postdocs at both Harvard University and the University of California, Davis. Tough, too, to ask assistants to spend six weeks working seven days a week as Ord did on Jamaica, where he video-recorded lizards' behavior at dawn and at dusk.

Those are the most important times to capture the lizards' actions because they, like birds, send signals at dawn and dusk that delineate their territorial boundaries, telling other males that the females within are off-limits. But Ord is the first to provide evidence that, unlike birds, the male anole lizard stakes out his territory using visual rather than vocal cues. Rather than chirping out a "chorus," all four species Ord followed in Jamaica use dewlap extension, head bobbing and/or step bobs—which resemble push-ups—as a way of defending their territory (Am Naturalist, 172:585-92, 2007).

"If [Ord is] correct in saying that this is the first study of the dawn/dusk 'chorus' phenomenon outside of the acoustic modality, then the study is important [in] recognizing the potentially more general nature of the phenomenon," Kevin de Queiroz, lizard biologist at the National Museum of Natural History in Washington, DC, wrote in an email.

What Ord observed, and was able to videotape and photograph (with effort—the average male anole lizard is only 12 cm end-to-end), were the spikes in physical activity as the lizards resumed their day perches or were about to abandon them as darkness fell. It was very clear that the time of day explained more variation in behavior than either temperature or the number of nearby adult males.

Male lizards engage in physical combat only when their visual signals fail to repel a territorial invader. If the signaling fails, the lizards will circle one another, lunging and sparring as each tries to bite the other. Sometimes they will whack one another using the side of their heads, and one or both can fall from their perches. Usually one lizard backs down early on, but fights can last as long as 40 minutes if they are evenly matched in size and physical strength.

Ord says that this research leads naturally to other questions that should be answered, such as a comparison of diet and foraging modes across lizards, birds and other chorusing species, whether they use vocal or visual signals to ward off competitors. He'd also like to do a comparative study across taxa that exhibit differences in signaling, territory, habitat, and other variables. "This would prove critical for identifying the functional origins of chorusing behavior," he predicts.

"For the time being, I'm knuckled down on looking at habitat influences on communication [just in the anole lizard], but it would be wonderful for somebody to investigate this in other species," Ord adds in an email. "Too many wonderful natural phenomena, too little time to study them all!" And no assistants willing to put in long hours tiptoeing after tiny lizards seven days a week.