Substrate excavation in the Namibian web-footed gecko, Palmatogecko rangei Andersson 1908, and its ecological significance

Abstract

Palmatogecko rangei Andersson 1908 occupies compacted windward dune faces in the Namib sand sea. It excavates burrows in this compacted sand and employs the webbed feet to both break and shift the sand. High speed cinematography of digging sequences revealed that the manus undergoes both sand breaking and sand shoveling cycles, with the former having about half the duration of the latter and involving a smaller arc of excursion of the limb and manus. The pes is used in sand shoveling also and is able to deposit the sand masses moved by the manus further to the rear. It is herein postulated that interdigital webs in Palmatogecko Andersson 1908 serve primarily in these excavatory processes and that their role as «sand shoes» in spreading the weight of the animal during locomotion is relatively minimal. The webs act as mechanical shovels and contain the loosened sand as it is transported posteriorly. Although psammophilous lizards are numerous and widespread, very few exhibit webbing of the toes. Most instead possess fringes on the digits that are used in weight support and excavating. Only in very particular sets of ecological circumstances do webs appear to be effective as alternatives to digital fringing.

Key Words:

• Namib desert
• Gekkonidae
• Palmatogecko
• excavation
• digital webbing