Reptiles exhibit extensive intraspecific variability in strategies for avoiding predators, particu-larly in response to changes in reproductive status, temperature or size (Pough, 1977, 1978; Vitt and Congdon, 1978; Shine, 1980; Bauwens and Thoen, 1981; Hertz et al., 1982; Huey and Hertz, 1982; Daniels, 1984). Reproductive status and tem-perature have been examined, but studies on the size related differences in defense strategies have emphasized mainly ontogenetic changes in exercise capacity. Juvenile snakes possess a reduced endurance capacity compared to adults because of a lower blood oxygen-carrying capacity (Pough, 1977, 1978) and juvenile agamids (Stellio stellio) are slower than adults (Huey and Hertz, 1982). The relationship between size and the effectiveness of defense strategies when approached by a predator is largely unknown, although Congdon et al.(1974) suggested that regenerated tails which are apparently fatter in Coleonyx variegatus could increase effectiveness of tail display for predator escape. However, tail loss as a measure of predation intensity under field conditions is confounded with difficulty. There are also possibilities of tail loss due to either social encounters or mechanical