Social and spatial patterns of two Afromontane crag lizards (Pseudocordylus spp.) in the Maloti-Drakensberg Mountains, South Africa

Understanding the evolution of vertebrate sociality requires comparative data on social associations across the vertebrate phylogeny. In the case of group-living lizards (i.e. species that live in stable social aggregations often associated with a shared resource), most work has focused on the Egerniinae in Australia, resulting in a taxonomic and geographic skew to our understanding of reptile sociality. The African cordylid lizards (Cordylidae) are also a promising system to study the evolution of sociality because grouping behaviour varies across the clade. Here, we studied the conspecific grouping behaviour of two crag lizards, Pseudocordylus langi and P. melanotus subviridis that occur at high elevations in the Maloti-Drakensberg Mountains of South Africa. To better understand their social organisation and mating system, we also present data on their spatial distribution, sexual dimorphism, and bite force. Both Pseudocordylus spp. were sexually dimorphic in morphology (males had larger heads than females of similar body size), colouration (males were more colourful) and female P. langi had a weaker bite force than males. Both P. langi and P. m. subviridis were associated with rocky habitat on the mountainside (e.g. cliffs, rock buttresses, and rock outcrops) and both were spaced apart and rarely in groups (79% of P. langi and 90% of P. m. subviridis were observed alone). Based on our findings, we hypothesise that both Pseudocordylus spp. have a territorial social structure and a polygynous mating system. This novel natural history information about crag lizards supports the assertion that Cordylidae is another model system for examining the evolution of sociality.