Intrasexual Behaviors in the Nonnative Mediterranean House Gecko, Hemidactylus turcicus

Abstract

Behavioral studies on introduced wildlife can provide valuable insight into its mechanisms of dispersal, habitat use, and the interactions it holds with the native fauna and flora. In this study, intrasexual (same-sex) behaviors of H. turcicus geckos were observed through staged interactions using size-matched subjects in a lab arena. Following baseline interaction tests, the same individuals underwent a topical treatment of either testosterone or sesame oil (control) alone. I tested for behavioral differences between the testosterone-treated and sesame oil-treated individuals, and I tested for an effect of testosterone within subjects. Lastly, I tested for a sex difference in the frequency of behaviors observed during the baseline tests. The behaviors recorded included aggressive (e.g. pushups, tail wags, bites), submissive (freezes and retreats), and neutral behaviors (e.g. approaches, licks, vocalizations). Behaviors expressed by testosterone treated males did not differ from the sesame oil-treated males. The same was true in the female treatment groups, where there was no difference between the treatments, and an overall absence of most aggressive behaviors. Secondly, no significant differences were found between the behaviors of the testosterone-treated subjects and their corresponding baseline results in either sex. Together, these findings suggest that short-term elevations of plasma testosterone do not have a direct influence on the expression of intrasexual behaviors in H. turcicus. Longer durations of testosterone treatments (e.g., weeks rather than 3 days) could result in different effects on the behaviors of H. turcicus geckos, and castration could also be used in future studies to test if a decrease in circulating plasma testosterone influences the expression of intrasexual behaviors of this House Gecko. Lastly, males were found to be significantly more expressive in both aggressive and submissive behaviors, than the females in the baseline tests. This is consistent with previous research on H. turcicus that reports males as being territorial and engaging in agonistic encounters, but females often participate in communal nesting with members of the same sex.