High temperatures constrain microhabitat selection and activity patterns of the insular Cape Verde wall gecko

Abstract

The diel activity, microhabitat selection and thermobiology were investigated in Tarentola substituta, a gecko endemic to an arid Cape Verde island, S. Vicente. Standardized transects were performed recording the microhabitat availability and the body, soil, refuge, air temperatures, relative humidity, gecko category (juvenile, adult male or female) and activity status for each observation. Thermal conditions were monitored with data-loggers. The activity pattern of the species was strictly nocturnal, as desert geckos. All individuals selected rocks as diurnal refuges, but adults used more medium-sized rocks (scarce) and juveniles small rocks (abundant). Such selection was mostly attributable to the refuges thermal properties: small rocks attained higher temperatures due to their lower thermal inertia. Geckos behaved as tigmotherms when active by night and as thermoconformers with the substrate by day. Nocturnal body temperatures did not differ among gecko categories or microhabitats. However, since juveniles selected small rocks, their diurnal body temperatures became higher, sometimes possibly risking overheating. Territoriality, scarcity of optimal refuges, high conspecific densities and lack of ground-predators may explain why juveniles use thermally suboptimal microhabitats. Results suggest that ecological shifts (nocturnality, microhabitat selection) and lack of competitors allowed T. substituta to adapt to the archipelago’s demanding arid and hot conditions.