Body Color and Morphological Correlates of Fitness in Eastern Fence Lizards (Sceloporus undulatus): A Spectrophotometric Approach

Abstract

Many lizards use colorful badges in displays with conspecifics during courtship and aggressive interactions. In Eastern Fence Lizards (Sceloporus undulatus), males and females reveal sexually dimorphic ventral abdominal coloration during social interactions and use these features to signal sex and perhaps other characteristics. However, the extent to which ventral badges or other chromatic features of males and females signal quality remains unresolved in this species. Additionally, adult S. undulatus exhibit temperature-dependent color change of their abdominal badges, a potential confounding variable in studies of the function of these badges. Here, we examined the relationship between spectral variables of ventral and dorsal skin color and morphometric traits linked to fitness in adult male and female S. undulatus under standardized temperature conditions. For males, ventral patch hue tended to decrease (i.e., was blue-shifted) as body size increased, whereas dorsal hue was unrelated to male size. In contrast, there was no relationship between ventral hue and body size in females, and dorsal hue increased (i.e., was red-shifted) with body size. In males, lower ultraviolet (UV) chroma and greater blue chroma of ventral abdominal badges predicted increasing body size. In females, UV chroma of the ventral abdomen was inversely related to body size and better body condition, whereas blue chroma was inversely related to body condition only. Dorsal UV chroma decreased with increasing body size in both males and females, but brightness was not a significant predictor of any morphometric trait in either sex. Overall, these results indicate that both blue and UV reflectance of ventral and dorsal abdominal skin are indices of size and thus age, and could therefore serve as indices of signaler quality in this species.