Abstract
Ozark hellbenders (Cryptobranchus alleganiensis bishopi) have undergone marked population declines across their entire distribution. A variety of ecological life history research has been conducted to determine the cause(s) of the declines. Historically, hellbender diet studies used stomach content examination methods; however, alternative approaches such as less intrusive stable isotope analyses are now options for researchers. The goals of our study were to conduct stable isotope analysis on live and formalin-preserved museum specimen Ozark hellbender tissues to identify diet composition in the Eleven Point and Spring rivers, Arkansas. Also, we used stable isotope analysis to investigate if Spring River hellbender diets have changed over time. We sampled fish, live hellbenders (non-destructively), and formalin-preserved hellbender tissues from museum collections for stable isotope analysis. We sampled crayfish for assemblage composition and stable isotope analysis. The results of our stable isotope study revealed three main findings: (1) there were no statistically significant differences between hellbender δ13C and δ15N values among sites and hellbender stable C and N isotopes were correlated with body length; (2) traditional δ13C versus δ15N bi-plots and trophic discrimination values did not provide complete discernment in hellbender diets; however, Bayesian MixSIAR models revealed hellbenders to be generalists, and (3) the use of δ13C and δ15N values adjusted historic formalin-fixed and ethanol preserved hellbenders matched well with current crayfish and fish stable isotope values based on Bayesian MixSIAR models. These findings provide important diet information and a possible tool to examine dietary patterns from preserved specimens that may be used for hellbender conservation and management.
Highlights
The Ozark hellbender (Cryptobranchus alleganiensis bishopi) is a large, long-lived (20+ years) benthic salamander that has undergone marked declines over the past five decades [1,2,3]
The goals of our study were to conduct stable isotope analysis on live and formalinpreserved museum specimen Ozark hellbender tissues to identify diet composition in the Eleven Point and Spring rivers, AR, USA, and to use stable isotope analysis to investigate if Spring River hellbender diets have changed over time (1970–1975 to early 2000’s)
Cambarus hubbsi was the dominant species at all stations except at EP2, where O. eupunctus shared a similar percentage of the total sample
Summary
The Ozark hellbender (Cryptobranchus alleganiensis bishopi) is a large, long-lived (20+ years) benthic salamander that has undergone marked declines over the past five decades [1,2,3]. Peterson et al [19] examined the seasonal prey items of Ozark hellbenders in the Spring River (Fulton, AR, USA) using gut contents, and documented crayfish as comprising at least 99% of hellbender diet in 7 months of the year. Alleganiensis) report cannibalism [23,24,25,26] and scavenging behavior [27] These findings support an alternative diet explanation that hellbenders undergo ontogenetic shifts in their diet and as adults are opportunistic feeders, which use a variety of congeners and conspecifics as food resources and utilize other taxonomic groups inhabiting the benthic habitat of hellbenders, such as Cottus and Etheostoma. Hellbenders may be eating crayfish in proportion to their availability in their benthic habitat; and supplementing with accessible food resources
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