Shelter microhabitats determine body temperature and dehydration rates of a terrestrial amphibian (Bufo marinus)

Selection of diurnal shelter sites varies significantly with season in the cane toad (Bufo marinus), and the aim of this paper is to determine how hydric and thermal conditions of shelter microhabitats changed with season and whether those changes explained seasonal differences in toad behavior. Body temperatures of cane toads were measured by telemetry and dehydration rates and thermal conditions of shelter microhabitats were measured by using preserved toads as environmental probes. Live toads and preserved toad models were monitored monthly over a 18-month period. Laboratory experiments showed that toad models dehydrated at the same rate as live toads. In the field, dehydration rates varied significantly between seasons and shelter microhabitats, but dehydration rates were always significantly less in shelters compared to a nonshelter control. Daily average body temperature of toads was 16-30degreesC, and it changed seasonally in proportion to model temperature. Diurnal model temperature was significantly lower in shelters compared to the nonshelter control, but there were significant seasonal differences between shelter sites. It appears that access to suitable diurnal shelter sites is essential for survival of cane toads outside the wet season and that seasonal changes in environmental conditions influence shelter microhabitat selection.