The Influence of Food Abundance on Territory Size in the Iguanid Lizard Sceloporus jarrovi

Abstract

This study was designed to determine how food abundance affects territory size for the insectivorous lizard Sceloporus jarrovi. Observations and experiments were performed in the field in southeastern Arizona during 1971 and 1972 summers. Territories were defined as defended areas, and the convex polygon method was used to determine territorial boundaries. Preliminary studies showed that all adult and most juvenile lizards defended territories against lizards of the same species, size, and sex. Sex and body size influenced territory size. Within size classes, territories of ♂ ♂ averaged more than twice territory size of ♀ ♀. Lizards in the larger size class had territories more than twice those of smaller animals. Natural food abundance, determined with adhesive—coated Masonite® boards, was inversely correlated with territory size. Summer territories compressed significantly when food was added even through natural food supplies seemed adequate. Terrtories returned to initial sizes with the removal of additional food. Experiments involving the locations of concentrated food sources within the territory provided some evidence for the hypothesis that ease of food obtainment may be an important factor in determining summer territorial size and location.