Ontogeny of Temperature Selection in Larval Amphibians

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Abstract
Ontogenetic shifts in final temperature preferenda were examined in larvae of 4 amphibian species. The mean thermal preference of all species increased with developmental stage and peaked at or shortly before metamorphic climax. Two ontogenetic patterns of thermal selection were observed. Pseudacris triseriata and Rana sphenocephala showed weak thermal preferences during the early to mid larval period, but strong preferences thereafter. Bufo americanus and Ambystoma texanum showed strong thermal preferences during all developmental stages. Ontogenetic shifts in preferred temperature may promote segregation of size classes within breeding habitats, thus reducing competition or cannibalism. Use of warmer microhabitats with age accelerates development at the end of the larval period when larvae become increasingly susceptible to habitat deterioration and predation. Developmental constraints may limit the effectiveness of thermoregulation in early developmental stages of certain species.