Body Size and Habitat Association as Determinants for Water Balance, Temperature Relations, and Behavioral...

The association between species' habitat preferences (e.g., aquatic, terrestrial, arboreal) and traits related to body temperature regulation and water balance has been relatively well studied in anurans. However, whether such associations hold for species occupying the same general habitat while differing in other relevant functional attributes remains poorly explored. Here, we studied the thermal and hydric physiology of five Neotropical frogs (Leptodactylus podicipinus, L. fuscus, L. mystacinus, L. macrosternum, and L. luctator) differing in body size and degree of association with water bodies, but known to co-occur in the same general habitat. We measured area-specific rates of evaporative water loss, skin resistance, area-specific water uptake, dehydration tolerance, thermal preference, thermal tolerance, and optimal temperature for locomotion. Area-specific rates of water loss and gain scaled negatively with body size, indicating strong allometric effects on water exchange. This size dependence, coupled with differences in dehydration tolerance, suggests alternative strategies for coping with desiccation, in which larger frogs rely on lower area-specific water loss to minimize desiccation risks, whereas smaller species compensate for their higher area-specific water loss through greater dehydration tolerance. In contrast, thermal preference and upper thermal tolerance showed limited interspecific variation and were unrelated to body size. Differences in thermal tolerance breadth were driven primarily by variation in lower thermal limits and showed no association with habitat preference. Field body temperatures were consistently lower than thermal preferences but remained within optimal ranges for performance. Our results indicate that even closely related species sharing the same habitat differed markedly in water balance strategies, highlighting how body size, dehydration tolerance, and thermal physiology interact to shape ecological performance.