Individual variation in the push -up display of Sceloporus lizards and its role in rival recognition

The push-up displays of the lizard genus Sceloporus are known to carry information regarding the species and sex of the sender. Males of this genus produce push-up displays in territorial encounters with conspecific males. Since a finite amount of energy is available to the individual for all activities, selection will favor behaviors that minimize the energy spent in defense of a territory. One such mechanism is the dear enemy phenomenon, a situation in which territory holders expend less energy in displaying to familiar than to unfamiliar conspecifics. An asymmetric war of attrition model of this process predicts that an individual will display less often over time to an initially unfamiliar opponent, presumably as the opponent becomes less of a threat to the resident\u27s territory. Because male Sceloporus are territorial, it is reasonable to predict that these patterns of behaviors will occur. I tested this by recording the frequency of displays given by a focal male toward familiar and unfamiliar opponents over three days. Display frequency was less toward familiar opponents and display frequency decreased in all pairings over three days. This is consistent with a war of attrition explanation of the dear enemy phenomenon. In order for the dear enemy phenomenon to occur, a resident must be able to distinguish between familiar and unfamiliar opponents. One way to do so is to identify them as individuals. In Sceloporus, the most obvious way for this information to be exchanged is via the push-up display. I examined several characteristics of male displays and found that the first portion of the display is unique to each male. Removing the first push-up from a display caused the loss of differential response to familiar and unfamiliar opponents by a recipient. This supports an hypothesis that some characteristic of the display indicates the identity of the sender