SEXUAL SIZE DIMORPHISM AND FEEDING ENERGETICS IN ANOLIS-CAROLINENSIS - WHY DO FEMALES TAKE SMALLER PREY THAN MALES

Costs of feeding were investigated in Anolis carolinensis to determine whether differences in feeding energetics related to sexual dimorphis m in head size could explain differences in average prey size taken by male and female lizards in the field. The amount of time required to subdue and swallow prey, as well as the oxygen consumed and lactate pr oduced during feeding, were measured for lizards feeding on a range of prey sizes. There was no difference between the sexes in the amount o f lactate produced during feeding. There were however, differences in the amount of time required to subdue and swallow prey and in the amou nt of oxygen consumed during feeding. Female lizards required more tim e and more oxygen to consume prey than did males. Energetic considerat ions, however, are probably not responsible for prey size differentiat ion as net energy gains are likely to be high and similar for the sexe s. While females do spend more time swallowing prey than males, the to tal amount of time to consume prey is a trivial part of a day. It is p robable that the amount of time available to females for activities ot her than feeding is a less important determinant of fitness than it is for males. However, the longer prey handling times may deter females from selecting large prey because of a probable increase in the risk o f predation.