Headbob Display Structure in the Naturalized Anolis Lizards of Bermuda: Sex, Context, and Population Effects

Many members of the Iguania group of lizards engage in stereotyped and species-specific ''pushup'' or ''headbob'' displays. Temporal attributes of displays have been quantified for a number of species in the genus Anolis, but few of these studies have examined effects on display structure of signaler sex, display context, and population. With this goal in mind we conducted a comparative study of three Anolis species permanently established (''naturalized'') on the island of Bermuda: Anolis grahami from Ja- maica, Anolis extremus from Barbados, and Anolis leachi from Antigua and Barbuda. These anoles are dis- tantly related to each other and to Anolis carolinensis—the only Anolis species for which all of the above influences on display structure have been examined in detail. Adults were field-captured and transported to the laboratory where paired interactions were videotaped and headbob displays analyzed. Results re- vealed one or more variables to exhibit sexual dimorphism in each species, and display context had little influence on signal structure. We then compared results from our founder populations on Bermuda with those published for two of our study species' source populations. No significant differences in headbob display units were found between A. grahami on Bermuda and on Jamaica. In contrast, male A. extremus on Bermuda produced fewer units per display than did males from Barbados, although the nature of the published data prevented statistical comparison.