Trophic Ecology Of An Imperiled Giant Salamander (Cryptobranchus A. Alleganiensis) In Southern Appalachian Streams

Eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) are large, aquatic amphibians that are a conservation priority in much of their range. However, our understanding of their role in aquatic foodwebs is limited. Prior gut content and observational studies suggest that their diet is predominantly comprised of crayfish but it is also possible that crayfish exoskeletons are less digestible than other food items (e.g., fish tissues). I examined the trophic position of eastern hellbenders in three streams in western North Carolina using analysis of d15N and d13C isotopes. I found that although hellbender trophic position did not vary among sites, hellbenders in the South Toe River (a site characterized by extremely low crayfish biomass) appear to have a diet comprised of both crayfish and benthic fishes. Additionally, hellbenders in this stream occupy a significantly higher trophic position than do some predatory fishes. These results suggest that, in some streams, hellbenders may function as apex predators and could potentially exhibit top-down control of aquatic community structure. Differences in diet across among river systems suggest that hellbenders do not feed exclusively on crayfishes and that they appear capable of altering their dietary strategies in response to changing resource availability.