Male collared lizards,Crotaphytus collaris(Sauria: Crotaphytidae), signal females by broadcasting visual displays

Abstract

The signalling function of displays broadcast when animals are distant from conspecifics can be difficult to determine. I tested the extent to which visually transmitted broadcast displays given by free-ranging territorial male collared lizards signalled same-sex rivals or females. One test involved recording the frequency of broadcast displays, aggressive contests with rivals, and courtship encounters with females during ten reproductive seasons when local sex ratios varied markedly. The frequency of broadcast displays decreased as the ratio of male competitors to females increased. The frequency with which males initiated contests with rivals was not related to the ratio of competitors to females, whereas the frequency of courtship interactions decreased with sex ratio because there were fewer females to court. The behaviour of males that defended territories during two successive seasons showed a similar pattern. Broadcast display frequency was positively correlated with courtship frequency, but not with the frequency of contests with rivals. Lastly, individual males gave more broadcast displays during focal observations when they also engaged in courtship encounters with females than other observations when they engaged in aggressive conflicts with rival males. Although these results do not reject the possibility that broadcast displays may also signal male rivals, they support a major role of these displays in advertisement to females.