BEHAVIORAL ASSESSMENT REVEALS SOCIAL AGGREGATIONS IN Petrosaurus thalassinus

Abstract

In a brief study on the endemic lizard, Petrosaurus thalassinus, in the Cañon de la Zorra region of Sierra La Laguna Biosphere Reserve in Mexico, over seven days we aimed to gain a preliminary insight into their social structure by examining their behavior, morphology, and habitat use. We captured, marked, and measured 28 adults, and conducted 19.4 hours of focal observations on 47 marked and unmarked adults in the field. Males had longer snout-vent lengths than females, but females had greater mass than males of the same snout-vent length. Lizards exhibited 30 behaviors organized into eight categories. Most notably, while basking on rocks or sharing crevices they aggregated in groups of two to five individuals (< 1m apart) and in frequent visual contact (25/47 observations, 53.2%) while basking on rocks or sharing crevices. Although aggregated lizards showed high levels of mutual tolerance and signaling behavior, they exhibited little to no aggression. Larger lizards used taller rocks and took higher positions on them, but there was no difference between sexes. Furthermore, we observed P. thalassinus in interspecific interactions with Sceloporus hunsakeri and with Ctenosaura hemilopha. Our results indicate that P. thalassinus could have a more complex social system than reported for most lizards, which warrants further investigation.