Incompletely protective refuges:: Selection and associated defences by a lizard, Cordylus cordylus (Squamata: Cordylidae)

Despite recent intel est in refuge use, refuge characteristics and their relationships to refuge-associated antipredatory defences have been relatively neglected. These topics were studied experimentally in the Cape girdled lizard, Cordylus cordylus. Lizards used crevices in novel situations under uncertain risk and when confronted by a human simulated predator. They preferred narrow crevices opening on only one side at ground level and orientated horizontally. Narrowness restricts access by predators, reduces detectability to a small visual angle and permits use of crevice-specific defences, making the lizards difficult to dislodge. Limiting openings to one side decreases detectability by reducing light, limits attacks to one direction and permits further withdrawal from any opening. Crevices at ground level confer greater distance from and reduced visibility to an overhead predator. Horizontal orientation may reduce visibility to an overhead predator, but the preference could be an artefact of the greater ease of entering horizontal crevices. Pheromonal labelling of crevices by conspecific males did not influence short-term crevice choices by males. Within crevices, C. cordylus pressed their dorsal surfaces against crevice roofs, pushing upward with their legs. They also positioned their tails to block access by predators to their bodies. We discuss these and related crevice-associated defences in other animals.