Rediscovery of 'lost' treefrogs from the Oaxacan highlands of Mexico

The Oaxacan highlands of Mexico boast an exceptional diversity of stream-breeding treefrogs (Hylidae). Recent surveys in these regions have reported dramatic declines for entire stream-breeding communities, and many endemic species have not been seen in several decades and are feared to be extinct. In 2007 we conducted a rapid survey in two focal regions that were surveyed in 1970 and 2000; both prior to and subsequent to reported population declines. We report on extant populations of six species missing from recent surveys following declines, one of which (Plectrohyla thorectes) had not been seen in over 28 years and was feared to be extinct. We document new populations of Exerodonta abdivita, a species previously known only from its type locality and currently listed as data deficient. We make comparisons with historical records and note changes in species composition and abundance with recent work. Differences in species compositions among studies may reflect population declines and rebounds over relatively short periods. However, we argue that aspects of species natural history in combination with the variable nature of brief surveys may account for some of the observed differences, and are important factors to consider when inferring species declines.