Tree lizard distribution and mating system: the influence of habitat and food resources

Abstract

We examined the distribution of an insectivorous iguanid lizard (Iguanidae: Urosaurus ornatus, tree lizard) in the Sonoran Desert of Arizona in 1984, 1986, and 1987. The purpose of the investigation was to examine the ecological correlates of lizard distribution and mating system. Data from 420 marked lizards which were captured 1552 times provided information on habitat-level differences in lizard numbers and characteristics of home ranges in which oviposition occurred. In addition, we evaluated the role of arthropod food resources in the distribution of female home range and in the mating status of males. In dry washes tree lizards occupied mesquite (Prosopis juliflora) trees, whereas in flatland habitat they lived in mesquite trees and other sites (dead mesquite and saguaro cactus, Carnegeia gigantea). Lizards were more abundant in dry washes than flatland habitat. The lizard mating system was variable and a greater proportion of males were polygynous in wash (33–67%) compared with flatland (7–33%) habitat. In the flatland, home ranges in which females oviposited could be distinguished from vacant sites by soil hardness, shrub cover, and the presence of wood rat (Neotoma albigula) nests. Arthropod abundance did not differ between female home ranges and nearest vacant site nor between habitats and among male territories. Therefore, food resource distribution does not appear to be a determinant of either female distribution or territory quality in male tree lizards.