Variation in Conspicuousness among Populations of an Iguanid Lizard, Sauromalus obesus (=ater)

Abstract

The appearance of an organism's color pattern is a function of numerous variables, including the background on which the organism is observed. Hence, color patterns that appear similar or conspicuous when taken out of context, may, in reality, appear quite different when viewed in a natural setting. I investigated the relative conspicuousness of chuckwallas, Sauromalus obesus (= ater) among three populations in which males differ in their coloration. The color pattern of male and female chuckwallas was compared to the background color of rocks on which individuals were observed basking or displaying. Data were also collected on predation pressures and the thermal environment to see whether there was any association with conspicuousness. Male tail and body conspicuousness, and female tail conspicuousness, varied among the three populations. In all populations, male tail color was more conspicuous than male body color and, within all populations, males were more conspicuous than females. However, males and females were not equally conspicuous among populations; females from one population were as conspicuous as males from a different population. Conspicuousness appeared to be negatively associated with predation pressures. Little evidence was found to suggest that thermal considerations influenced color variation among the three populations. The role of chuckwalla conspicuousness is also discussed in the context of sexual selection.