The effects of food level and conspecific density on biting and cannibalism in larval long-toed salamanders, Ambystoma macrodactylum

Previous studies have examined abiotic and biotic factors that facilitate a gonistic behavior. For larval amphibians. food availability and conspecific density have been suggested as important factors influencing intraspecific aggression and cannibalism. In this study, we examined the separate and co mbined effects of food availability and density on the agonistic behavior a nd life history of larval long-toed salamanders, Ambystoma macrodactylum. W e designed a 2x2 factorial experiment in which larvae were raised with eith er a high or low density of conspecifics and fed either a high or low level of food. For each treatment, we quantified the amount of group size variat ion., biting, and cannibalism occurring. Additionally, we examined survival to, time to and size at metamorphosis for all larvae. Results indicated th at differences in both density and food level influenced all three life his tory traits measured. Moreover, differences in food level at which larvae w ere reared resulted in higher within-group size variation and heightened in traspecific biting while both density and food level contributed to increas ed cannibalism. We suggest that increased hunger levels and an uneven size structure promoted biting among larvae in the low food treatments. Moreover . these factors combined with a higher encounter rate with conspecifics in the high density treatments may have prompted larger individuals to seek an alternative food source in the form of smaller conspecifics.