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 re lationships to refuge-associated antipredatory defences have been relativel y neglected. These topics were studied experimentally in the Cape girdled l izard, Cordylus cordylus. Lizards used crevices in novel situations under u ncertain risk and when confronted by a human simulated predator. They prefe rred narrow crevices opening on only one side at ground level and orientate d horizontally. Narrowness restricts access by predators, reduces detectabi lity to a small visual angle and permits use of crevice-specific defences, making the lizards difficult to dislodge. Limiting openings to one side dec reases detectability by reducing light, limits attacks to one direction and permits further withdrawal from any opening. Crevices at ground level conf er greater distance from and reduced visibility to an overhead predator. Ho rizontal 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 in fluence short-term crevice choices by males. Within crevices, C. cordylus p ressed their dorsal surfaces against crevice roofs, pushing upward with the ir legs. They also positioned their tails to block access by predators to t heir bodies. We discuss these and related crevice-associated defences in ot her animals.