Interaction of Testosterone and Social Stimuli on the Feeding Behavior of Male Mountain Spiny Lizards, Sceloporus jarrovi

Abstract

Experimental elevation of plasma testosterone during the nonbreeding season has previously been shown to reduce the survivorship of male mountain spiny lizards, Sceloporus jarrovi. The reduction in survivorship results from energetic stress caused, in part, by reduced foraging behavior. This study examines proximate explanations for this decreased foraging behavior. In particular, do testosterone-treated males engage in more social behaviors at the expense of feeding? This question was tested by observing the behavior of hormonally manipulated males in a large indoor arena in which both social and prey stimuli were present. Males were tested with social stimuli present during the nonbreeding season (male intruders, sexually unreceptive females, or a combination of male and females) and with stimuli encountered only during the breeding season (sexually receptive females). Testosterone-implanted males ate significantly fewer prey when a sexually receptive female was present, but control males did not. However, a difference in feeding was not observed in any of the nonbreeding stimulus conditions in spite of consistent increases in social behaviors, such as display frequencies. These results indicate that, although high levels of testosterone increase some aspects of social behavior, they do not necessarily lead to decreased feeding in the nonbreeding season.