Temperature exposure and possible thermoregulation strategies in the Titicaca water frog Telmatobius culeus, a fully aquatic frog of the High Andes

Abstract

Temperature has an important effect on amphibians, influencing virtually all physiological systems. Thermoregulation is used to manage unfavourable thermal conditions, but has been poorly studied in aquatic amphibians, and no information is available for adult aquatic anurans. We studied the temperatures to which the Critically Endangered and high Andean fully aquatic Titicaca water frog Telmatobius culeus is exposed and investigated possible thermoregulation strategies of the species in the wild. We measured water temperature in different seasons, microhabitats and depths at which T. culeus is most abundant. We established transects to obtain population densities and activity patterns of the species during the day. Seasonal and daily temperature variations as well as temperature variations among depths and microhabitats were noted. These variations were associated with densities of visible T. culeus, where adult densities were higher at depths with more stable temperatures. T. culeus behaviour associated with thermoregulation strategies in the aquatic habitat included depth selection and movement of individuals between different microhabitats. Selection of microhabitat depended on the temperature at a site and the hour of the day. These results indicate possible behavioural thermoregulation strategies such as movement to different sites or basking used by a highly specialized amphibian, and provide insights into how aquatic benthic organisms use strategies for thermoregulation in aquatic heterogeneous environments. These strategies are probably also used by other aquatic organisms from the tropical Andes. Knowledge of how these organisms respond to temperature could also help to understand the impact of global warming on their status.