Sex Ratio, Group Composition and Male Spacing in the Large-Scaled Girdled Lizard, Cordylus macropholis

Sex ratio, group composition, and male spacing were studied in Cordylus macropholis, a terrestrial lizard that inhabits the succulent Euphorbia caput-medusae. Repetitive sampling of two populations revealed highly female-biased sex ratios for adult, as well as juvenile size classes. The near 1:1 ratio observed in the smallest size class, however, suggests that the sex-ratio is 1:1 at birth. Sex ratio was found to relate positively to population density. Among aggregations containing more than one adult individual, a composition consisting of a male/female pair with or without juveniles, was the most common. Few cases were recorded where an adult male shared a plant shelter with more than one adult female or with another adult male. Adult males were randomly spaced among plants, both in and outside the mating season. Data on group structure and male spacing, especially the lack of clear differences between the mating and the nonmating season, provide little indication that male territoriality may be the cause of the highly female-biased sex ratio recorded for C. macropholis in the E. caput-medusae habitat.