Anti-predation behaviour of Dickerson's collared lizard, Crotaphytus dickersonae

Males of Dickerson's collared lizard (Crotaphytus dickersonae) are conspicuously bright blue in colour and can be detected at great distances. In contrast, females are brown and much less conspicuous. Given the visibility of males to predators, the question arises how they avoid predation and whether the sexes differ in anti-predator behaviour. Using a slowly approaching human as a simulated predator, approach and flight distances were recorded, as were the presence of other anti-predation responses such as pursuit deterrence signalling, distraction behaviour and aggressive threat. The lizards were captured and physical data such as cloacal temperatures, weight and snout-vent length were obtained. To assess further the effect of coloration on predation pressure, test subjects were painted to make them inconspicuous (brown) or conspicuous (blue) and recaptured after a week. After shedding their painted skin, subjects were approached one final time. Few direct relationships were found between anti-predation displays and body weight, size or temperature. Exhibition of pursuit deterrence signalling or distraction behaviour was rare, and no subject displayed aggressive behaviour (except when caught). Interestingly, males fled sooner, and tended to use more refuge than females, which probably indicates stronger predation pressure on males. However, an overall low use of refuge, the observer's ability to approach most subjects closely before they fled, and few sightings of potential predators, suggest that weak local predation pressure helps to explain why sexually selected conspicuous male coloration has been able to evolve in C. dickersonae.