Characterizing territoriality and the mechanisms that mediate it in female Anolis gundlachi lizards

Abstract

Territoriality is a suite of behaviors through which animals secure access to particular areas or resources. It is prevalent across animal groups and has the potential to exert substantial influence on fitness by mediating how individuals are distributed across the landscape, which individuals interact socially, and those that have access to resources. Territoriality has been the subject of extensive research on animal behavior over the last century and has influenced our understanding of other aspects of species ecology, such as mating systems. However, a substantial portion of research on territoriality has focused primarily on males, despite the fact that females of many species are also observed to exhibit territoriality. This is particularly true of studies investigating the mechanisms that modulate territoriality, such as circulating hormones and morphological characteristics including body condition. As such, two important questions remain open for many territorial taxa--within territorial species, do both sexes use similar repertoires of territorial behavior, and if so, are these behaviors mediated by the same mechanisms in both females? The aim of this dissertation has been to pursue these two questions in the lizard Anolis gundlachi. Anolis have figured prominently in territorial research over the last century but are plagued with the same pitfall of lack of studies of females, which is a common problem across many groups, as is observed in other species. Integrating field studies and laboratory techniques, I characterized the behavior and space use of free-living female A. gundlachi in Puerto Rico to assess whether females exhibit similar behavioral patterns as males. As part of this research, I assessed the potential for individual variation in body condition to mediate differences in territory size. I also characterized the testosterone and corticosterone profiles of free-living male and female A. gundlachi, and staged territorial intrusions among females to evaluate the potential for these hormones to mediate differences in territorial behavior across the sexes and among females. Finally, I evaluated the potential for a tradeoff between testosterone, corticosterone, and parasite load by measuring parasite loads of Plasmodium sp. in the same free-living population. Together, the results presented in this dissertation demonstrate that female A. gundlachi exhibit territorial behaviors that highly resemble those observed in male A. gundlachi and other species of Anolis. However, two mechanisms commonly implicated in the control of territoriality in males--metrics of body size and circulating hormones concentrations--did not explain similar patterns in females. In addition, we found no evidence of a tradeoff between hormone concentration and parasite load. Taken together, these results demonstrate that different mechanisms may influence similar behaviors exhibited by males and females of the same species. In combination with a growing body of work investigating the evolution of territorial and other aggressive behaviors in females, our findings demonstrate the need for more direct studies of females to more clearly understand why these behaviors have arisen in both sexes and to identify the mechanisms that mediate them in females.