Population Dynamics of Hylodes uai Tadpoles (Anura, Hylodidae) in a Tropical Forest Stream, Southeastern Brazil

Currently there is limited information on the population dynamics of tadpoles, particularly in the Neotropical region. Because of this dearth of information, studies on the temporal distribution of different tadpole developmental stages are important for understanding the dynamics of these organisms in their aquatic environment. We studied the temporal distribution of the Torrent Frog Hylodes uai tadpoles, and their relationship with rainfall, in an Atlantic Rainforest-Cerrado ecotone in Southeastern Brazil. There is no previous information on population dynamics for this tadpole species. We sampled 42 m along a forest stream between April 2003 and March 2005. Tadpoles occurred during all months. Tadpoles in initial developmental stages (up to Gosner stage 25) represented 66.7% of sampled individuals and occurred throughout year, suggesting continuous and prolonged reproductive activity. Body length in tadpoles varied between seasons and among developmental stages. Overall tadpole density varied from 0.024 to 0.67 tadpoles/m of stream and was higher in the dry season, which may be an adaptation to target their metamorphosis to the rainy season. The main microhabitat used by tadpoles was under stones, and there was a tendency for tadpoles with smaller body size to occupy shallower stream portions. Our study contributes to the understanding of tadpole dynamics in tropical forest streams and adds information on the ecology of a stream-dwelling amphibian.