Individual and sex differences in the use of the push-up display by the sagebrush lizard, Sceloporus graciosus

Abstract

Repeatable differences among individuals or among groups of individuals within a population may be used to describe the existence of alternative ‘strategies’ or social roles in behaviour and constitute the raw material on which phenotypic selection can act. Communicative displays that show consistent differences among individuals or between the sexes may also be used as mechanisms for individual or sexual recognition. In this study, individual and sex differences in several aspects of the push-up display were examined in a field study of Sceloporus graciosus. Previous studies have looked primarily at specifics of the head-bob pattern of adult male lizards in captivity. This study investigated several other measures of the push-up display, including display frequency, display perch height and number of legs flexed in displays as well as the head-bob pattern. It also examined the behaviour of both adult male and female lizards in the field. Repeatable individual differences occurred in all of the variables examined. These differences may be indicative of differences in home-range quality, motivational state, or may be used for individual recognition. Differences between the sexes occurred in display frequency, number of head-bobs per display and display duration, but not in display perch height, nor in number of legs flexed per display. Sex differences in the head-bob pattern suggest that the push-up displays of males and females may be qualitatively different, and possibly used for different purposes.