Prey's traits mediate a neotropical toad diet

1. Despite the widespread occurrence of myrmecophagy in anurans it is generally unclear whether ant-specialists feed on ants opportunistically or whether they preferentially select for certain species, potentially favoring specific morphological, ecological, or nutritional traits. 2. We flushed 105 stomachs of a lowland neotropical toad, Rhinella alata, and identified each consumed ant to species level. We used linear selectivity to calculate predator preference by comparing the abundances of consumed species to their abundances in the leaf litter community on Barro Colorado Island, Panama. We conducted multiple regression models to test whether linear selectivity or general predator preference related to seven morphological characteristics and two measurements of nutritional content. 3. Rhinella alata preferentially harvested 24 ant species. Other species were either avoided (n=34) or were eaten opportunistically (n=26). We found that R. alata predominantly preys upon large ants that are textured with hair and/or rugosity and preference for prey did not relate to nutrition content. Rhinella alata avoided small ants even if they were hyper abundant in the environment, and preferentially ate chemically-defended and aggressive ants if they were large enough. 4. We propose that R. alata prefers large ants because they represent a more efficient prey item in terms of predator handling time and because they are easier to see than are smaller ants. Furthermore, we hypothesize that R. alata predation attempts are more successful when prey are textured because microstructures on the tongue and prey surface may increase prey adhesion. 5. The ant specialist R. alata is not specializing on any particular ant species but rather maximizing prey quantity over quality by only eating the largest ants, despite their scarcity in the environment.