Social Structure of the Spiny-Tailed Iguana, Ctenosaura Similis

Animal social structure, the social connections and patterns of interactions, its personality, and its genetic relatedness can affect a variety of ecological process within a species, including dispersal, predator evasion, disease transmission, and mate acquisition. While animal social structure has been examined in many mammals, birds, fish, and insects, they have not been widely examined in reptiles. There are few studies that have looked at the social structure of lizards, despite the widespread importance of these species. The Spiny-tailed Iguana (Ctenosaura similis) is a common species throughout it range, from southern Mexico through Panama. In Palo Verde National Park, C. similis forms facultative stable groups with high site fidelity around anthropogenically disturbed sites, using building roofs, crevices, and other material for retreat locations. The characteristics of such groups suggests that there may be adaptive reasons for their formation, but the social structure of C. similis has not been examined. In this study, a group of ~28 lizards were analyzed for association patterns, genetic relatedness, and personality. DNA microsatellite markers (derived from blood samples) were used to examine the pairwise genetic relatedness of associating lizards, as well as the genetic structure of the group. Personality assays were conducted to determine evidence for personalities in C. similis as well as correlated behavioral traits, or behavioral syndromes. Association patterns were collected using physical proximity tags that recorded interacting individual lizards; association patterns and the the social structure were quantified by using social network analysis, a methodology used to study the social relationships of many animals at one time. The effects of retreat co-location, genetic relatedness, personality, conspecific aggression, and morphometric values on association patterns were examined to understand their contribution, if any, to the non-random patterns seen in animal associations. Genetic structure was lacking in the group with no obvious sex dispersing and there was evidence for inbreeding. This study revealed strong support for stable personalities, behavioral syndromes, and network positions of individual animals. Subgroups were found in the social structure, and animals were stable in their number of direct social connections for each seasons. Animals had many social connections of varying strength suggesting the social structure may be insulated from conspecific loss and other disruptions. Overall this study has closed significant gaps in our knowledge about the social structure and behavioral characteristics of C. similis in Costa Rica