Retreat site occupation and short-term movements in an oasis-dwelling frog in relation to temperature-humidity conditions

Abstract

The roles of temperature and humidity in shaping diurnal retreat site occupation and short-term movements in amphibians in desert environments have scarcely been studied. In this work, we investigated retreats and movements in the painted frog (Discoglossus pictus auritus) that inhabits oases in arid southern Tunisia, by using a composite temperature-humidity index (THI). Our results show non-random occupation of retreat sites with respect to prevailing temperature-humidity conditions. When leaving retreat sites with THI values above or below their preferred levels, painted frogs tended to move to sites with THI levels more similar to their preferred conditions. We also found that large individuals tended to occupy retreat sites offering similar THI levels, while small individuals moved between sites with very different THI levels, a pattern that could be driven by age-dependent experience. However, there was no significant relationship between the distance moved by painted frogs and the magnitude of the change in the THI between occupied sites. In summary, our findings evidence the role of temperature-humidity conditions in shaping the patterns of diurnal retreat site use in an arid zone amphibian. They also underline the usefulness of composite temperature-humidity indices when assessing amphibian-habitat relationships.