Ecological and Demographic Correlates of Injury Rates in Some Bahamian Anolis Lizards

Abstract

Raw tail-break frequencies in certain insular Anolis lizards are positively correlated with survival rates. Estimated intensity of predation, on the other hand, negatively correlates with survival rate and is greater on islands with more predatory bird species and in more open habitats. Estimated efficiency of predation upon A. sagrei females is greater in open habitats than in forests. Males have higher per-unit-time injury rates (tail, front toes, back toes) than females in A. sagrei and A. distichus, but not in the less territorial A. angusticeps. Front-toe injury rates are on one of three islands positively correlated with conspecific density; this is a likely kind of injury to result from intraspecific interaction. Tail-break and back-toe injury rates are more frequently negatively correlated with conspecific density; they are perhaps more likely to result from predation, in which case the correlation may reflect a depressive effect of predation on population size. The fraction injured in a population increases regularly with body size. Such curves, corrected for differential growth rates so as to reflect age, show the opposite relation of injury rate to habitat type than do the body-size curves. Three Anolis species differ little in injury rates, but a fourth, A. carolinensis, has an unusually low number of tail breaks.