Anole displays consist of conspicuous behaviors that are known to be used in multiple contexts, such as exhibiting territory ownership and territory defense, mate attraction and female receptivity, species recognition, and even predator deterrence. As most of you know, the display repertoire typically involves three major signal types: “dewlap extensions” (DE, pulsing of the throat fan or dewlap), “push-ups” (PU, up and down movement of the body and tail), and “head-nods” (HN, up and down movement of the head only). Although the visual display behavior in anoles has been extensively studied, the function of these three major signal types (DE, PU and HN) remains highly equivocal, and especially in the brown anole. Therefore, we decided to set up a behavioral experiment addressing DE, PU and HN signaling rates across diverse contexts, using the brown anole as study species.
Our study differed from previous ones in two main aspects. Whereas most other studies have focused on male signaling only, we looked to the three separate signal types in both male and female lizards. Secondly, our study is the first one to compare display rates across a wide range of contexts using the same individuals over again (repeated-measures design). This design could, however, only work under fully-controlled laboratory testing conditions. The diverse contexts we tested included predator, non-predator and several social interactions (i.e., mirror, male-male, male-female and female-male). For the predator and non-predator interactions, we used a living curly-tailed and equally-sized ocellated spiny-tailed lizard, respectively; the social context involved only conspecific interactions. Rather than examining display structure, we focused on the frequency with which each individual signal type was performed.
What did our results show? We found that brown anoles of both sexes exhibited higher display rates in the presence of conspecifics than when confronted with a predator or non-predator. DE, PU, and HN seem to be of main importance during brown anole social interactions, and thus not in predator deterrence. Whereas the females did not significantly raise display rates in response to a mirror or during intersexual interactions compared to a control situation, males did. The PU signal type only appears to play a major role for brown anole males during aggressive encounters. On the other hand, increased frequencies of all signal types during male-female interactions suggest that DE, PU, and HN are all essential for male courtship.
Finally, we suggest that intersexual selection is probably a driving force for frequency-related dewlap use in both sexes (we found a very strong, but not significant, trend that females increased their DE frequency only during female-male interactions). In contrast, pronounced intersexual differences were detected for PU and HN rates within a social context. I would like to mention once more that all our behavioral experiments were conducted under controlled laboratory conditions and that caution is needed on the general interpretation of our findings.
To end, I would like to say that we did experience some difficulties in comparing our PU and HN results with results from previous studies on brown anole display behavior, due to an inconsistent terminology found in the literature. Authors have variously used the terms “nod,” “headnod,” “bob,” “headbob” and “pushup” to refer to the stereotyped bobbing display and it is not always clear which movements correspond exactly to which terms (e.g., only head movement, only front legs, whole body movement including/excluding tail). Partan et al. (2011) did a very nice job by discussing several bobbing display terms in her paper, but still we think there is need for a more consistent and defined “bobbing” terminology. In this way, pooling display datasets and comparing display results will become more efficient and accurate, which in turn may lead to better “anole science”!
Driessens, T., Vanhooydonck, B., Van Damme, R. 2014. Deterring predators, daunting opponents or drawing partners? Signaling rates across diverse contexts in the lizard Anolis sagrei. Behav Ecol Sociobiol 68:173–184.