Social Life on the Rocks: Behavioral Diversity and Sexual Selection in Collared Lizards (pp. 213-246)
Authors: (Troy A. Baird, University of Central Oklahoma, OK, USA)
Abstract: Collared lizards, Crotaphytus collaris, are restricted to patches of exposed rock habitat using elevated perches to sight arthropod prey, but have also colonized flood-control spillways. These homogenous boulder fields facilitate life-long observation of the same individuals beginning as hatchlings. Studies in my laboratory have revealed a marked influence of sexual selection and the evolutionary costs and benefits of aggression on social behavior. Large males are conspicuously colored which promotes advertisement to females and rival males. Mature first-year males adopt stealthy space use and social behavior and their coloration is less conspicuous which promotes effective foraging and fast growth. Social tactics are plastic in both sexes. Females defend core areas when foraging perches are limited, but not when they are abundant. First-year males quickly shift to territorial tactics when older territorial males are removed experimentally or by predators. There is also marked within-season temporal variation in territorial behavior. Re-establishing occupancy does not require intense aggression early each season because philopatry to the same territories is high. Instead, males invest in courtship early and postpone the highest rates of advertisement until frequent display did not detract from opportunities to court and mate. At mid-season, experienced males reduce their defense costs by responding to challenges less aggressively than do inexperienced males. Courtship frequency was much higher in territorial than non-territorial males, and correlated best with the frequency of visually broadcast displays. Microsatellite studies of paternity indicate, however, that non-territorial males sire a surprisingly high percentage of hatchlings. Sneaking tactics may be particularly effective because homogeneous expanses of habitat allow first-year males to hide while remaining near to females that choose to mate with multiple males and produce as many as four clutches per season.