Seasonal changes in the thermal tolerances of Odontophrynus occidentalis (Anura: Odontophrynidae)

Abstract

We studied the thermal tolerances of Odontophrynus occidentalis during the dry and wet seasons of the Monte Desert in San Juan Province, Argentina. This toad had differences in critical thermal maximum (CTmax) between dry and wet seasons, and the CTmax values were greater in the wet season (Austral summer). Operative temperature, body temperature and environmental maximal temperature were related to CTmax suggesting seasonal acclimatization in O. occidentalis. Additionally, the CTmax recorded for O. occidentalis was 36.1 ºC, and the maximum ambient temperature recorded during the toads’ activity time was 37 ºC. Also, the CTmin recorded for O. occidentalis was 4.1 ºC and minimum environmental temperatures were recorded as 7.2 ºC. The wide tolerance range observed and the relationship between tolerance limits and the environmental temperature extremes indicate that seasonal acclimatization is an effective mechanism by which toads can raise their thermal tolerance allowing them to survive in the challenging conditions of the Monte Desert.