The data contained in McCoy et al American Naturalist 2011 data contains mortality data for Agalychnis callidryas tadpoles from predation experiments with a water bug predator (Belostoma sp.) and predatory dragonfly nymphs (Pantala flavescens). The data are for two separate experiments. One experiment used tadpoles that were mixtures of size classes, where as the other used homogeneous sized tadpoles. These experiments were conducted between June and August 2008 at the Smithsonian Tropical Research Institute?s field station in Gamboa, Panama? (9? 7'14.04"N, 79?42'16.67"W). Please contact Dr. Michael W. McCoy (anura@ufl.edu) or Dr. James R. Vonesh with questions. In the data file there are 9 columns these are 1. replicate block: This column provides a numeric identifier of each replicate of the experiment. 2. initial tadpole size specific density: This column applies only to the mixed-size classes experiment. It identifies the number of tadpoles of each size class that were used in the experiment 3. initial total prey density: This column identifies the total number of tadpoles added to each experimental unit at the start of the experiment (for the mixed-size class experiment this identifies the total number of tadpoles including all size classes added to each tank) 4. cohort type: The column identifies which experiment that data are from. Mixed-sizes indicates data for the mixed-size class experiment and single sizes indicates the data are from the homogenous sized prey experiment. 5. predator identity: identifies the predator species used. Dragonfly indicates that the predator was nymphs of the dragonly Pantala flavescens, and Waterbug indicates the predators was a predacious water bug of the genus Belostoma. 6. size class: A categorical description of the 5 size groups used in both experiments. 7. median predators: the median number of predators per tank that remained to the end of the experiment. For dragonflies, each tank had 3 predators initially, whereas for waterbugs each tank only received 1 predator. 8. number tadpoles eaten: The difference between the number of tadpoles added to each tank at the start of each trial of the experiment and the number remaining at the end of each trial. 9. tadpole total length: The average total length of tadpoles of each size class added to each tank. These data represent the length of the distance from the tip of the snout of the tadpoles to the tip of the tail. The units are in millimeters.