Using DNA metabarcoding to assess dietary selection and seasonal dietary patterns in eastern hellbenders (Cryptobranchus alleganiensis)

Understanding trophic classifications (i.e., specialist/generalist) of predators is important as dietary selection can predict resilience to environmental change. Eastern hellbenders (Cryptobranchus alleganiensis) are large, fully-aquatic, and highly imperiled amphibians thought to specialize on crayfish. However, historical studies examining hellbender diet used visual analyses, potentially underestimating soft-tissue or fast-decaying prey. Thus, their specialist classification has been recently challenged and there is a need to understand hellbender dietary patterns and trophic classifications using contemporary techniques. The goal of this study was to use DNA metabarcoding, a genetic technique useful for identifying organic material, to examine diet and dietary selection of hellbenders across three streams in North Carolina, USA. We performed gastric lavage on 77 unique adult hellbenders to collect 81 stomach content samples across spring (n = 35) and summer (n = 46), then identified stomach contents using microscopy and DNA metabarcoding. We identified spring stomach contents prior to summer to identify the most commonly consumed prey orders. Then, we surveyed prey availability of those orders (Decapoda, Cypriniformes, Perciformes, Scorpaeniformes, Urodela) in the summer to determine summer dietary selection within a use-availability framework. We identified 394 individual prey items across seven classes, 19 orders, 35 families, 56 genera, and 55 species. We found that hellbenders significantly preferred Decapoda over other orders and consumed significantly more prey items (particularly Decapoda) in spring compared to summer. Our findings indicate that hellbenders preferentially consume crayfish, but opportunistically consume a wide variety of other prey, supporting a trophic classification of facultative specialists in our focal system.