Living in Patchy Habitats: Substrate Selection for Basking by Sympatric Lizards in Contrasted Anthropogenic Habitats in Western France

The influence of temperature on the physiological processes in reptiles is well known, for example growth, reproduction, muscular energy are all largely temperature dependent and therefore temperature is a key aspect of reptilian ecology. However, there may be constraints on the ability of reptiles to harness thermal energy, particularly during cold seasons in the temperate zones. Substrate selection is a key aspect in thermoregulation and can enhance heat uptake. For example, wood substrates are known to increase rates of heat gain in basking reptiles enabling earlier attainment of optimum body temperatures compared to other substrate types, which enables increased time available for other activities. In this paper we describe substrate use for basking in two species of lizard, Lacerta bilineata and Podarcis muralis in a hedgerow and suburban garden in western France compared against a null model of substrate availability. When different substrates were pooled based on their material similarities both species were recorded in greater frequency on wood based materials in comparison to their availability compared to non-wood substrates. However at a finer level, in comparison to substrate availability (fallen tree branches, tree stumps, open ground etc), P. muralis showed strong substrate selection for basking, whereas L. bilineata did not depart significantly from the null model. We speculated that intra-specific aggression in L. bilineata was a possible cause of this result due to dominant individuals limiting smaller or female lizards from accessing prime basking sites. Differences in communal basking between the two species supported this notion.