This study describes the diet composition and prey selection of the Endangered Junín giant frog Telmatobius macrostomus, endemic to the central Andes of Peru. Prey items were recovered by forced regurgitation of stomach contents through gastric lavage. Top prey taxa in all samples (n = 9) consisted of a snail (Mollusca: Gastropoda: Hygrophila: Physidae; 78% frequency of occurrence) and an amphipod (Arthropoda: Malacostraca: Amphipoda: Hyalellidae; 56% frequency of occurrence). T. macrostomus appeared to select snails (family Physidae) and mayflies (family Baetidae) from the available prey in the environment. No vertebrate species were found in the stomach contents. Only 9 adults were found during this study (survey effort = 8.9 person-hours per frog), suggesting that adults of this species are rare and/or difficult to find. Although our sample size is limited, and the results need to be interpreted with caution, these findings provide important basic ecological data that can prove useful in the conservation of this species.

The Junín giant frog Telmatobius macrostomus (Peters, 1873) is an Endangered and endemic frog in the central Andes of Peru. However, no quantitative ecological data exist to facilitate characterization of T. macrostomus habitat, nor do estimates of occupancy and detection probability, all of which are vital to inform appropriate management decisions. We present novel data on the current distribution and habitat of T. macrostomus in 3 natural protected areas in the regions of Junín and Pasco, Peru. To provide a general description of the areas where T. macrostomus occurred and did not occur, we measured a variety of physical, chemical, and biological conditions. We found T. macrostomus in fewer than half the streams surveyed for an estimated occupancy and detection probability of 0.40 ± 0.11 SE and 0.84 ± 0.06 SE, respectively. Akaike's information criterion (AIC) indicates that of the 20 single-variable models constructed during this study, 5 were substantially associated with T. macrostomus occurrence (Δ corrected AIC [ΔAIC c ] < 2). The % Chironomidae metric of benthic macroinvertebrate communities at sampled sites best predicted the occurrence of T. macrostomus, followed by pH. Specific conductance, % silt and rainbow trout Oncorhynchus mykiss were also associated with T. macrostomus occurrence. Although the most parsimonious multi-variable occupancy model only included % Chironomidae, pH and rainbow trout as predictive variables of T. macrostomus occurrence, the other singlevariable models with apparent influence over T. macrostomus occurrence may also be used to identify adequate areas for Junín giant frog conservation.