Colonization of novel White Sands habitat is associated with changes in lizard anti-predator behaviour

Colonization of novel habitats is often associated with differences in ecological community composition. For small diurnal animals, differences in predator diversity and abundance can lead to behavioural shifts in the novel habitat. The eastern fence lizard Sceloporus undulatus (Bosc and Daudin, 1801) recently colonized the gypsum dunes of White Sands, a predator-poor community relative to the predator-rich community of the surrounding Chihuahuan dark-soil habitat. We used field experiments to assess S. undulatus anti-predator behaviour in white-sand versus dark-soil habitats, and used laboratory assays to determine whether behavioural differences could be mediated by hormonal regulation. Overall, we found that white-sand lizards were less vigilant but more wary than their dark-soil counterparts; it took them longer to detect a simulated predator, but once detected they were more likely to retreat from their perches than dark-soil lizards. At the proximate level, differences in anti-predator behaviour could not be explained by differences in plasma hormone levels (corticosterone and testosterone); we detected elevated corticosterone for lizards in our stress treatment relative to control treatment, but found no differences between habitats in baseline or acute corticosterone levels. At the evolutionary level, we suggest that differences in anti-predator behaviour may be explained by differences across habitats in predation environment, habituation, and/or the cost of retreating. Our study implicates changes in predator community composition in mediating ecological divergence in behaviour. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 657–667.