Hellbender Salamanders (Cryptobranchus alleganiensis) Exhibit an Ontogenetic Shift in Microhabitat Use in a Blue Ridge Physiographic Region Stream

Organisms that experience large changes in body size during the life span often exhibit differences in resource use among life stages. Ontogenetic shifts in habitat use reduce intraspecific competition and predation and are common in lotic organisms. Although information on the immature life stages of the Hellbender (Cryptobranchus alleganiensis) is limited, this aquatic salamander exhibits ontogenetic shifts in habitat use in some streams, with adults sheltering under large rocks and larvae utilizing interstitial spaces of gravel beds. Due to the geomorphology of Little River, Tennessee, however, limited interstitial spaces within the gravel are often filled with sand. Therefore, we quantified microhabitat parameters for three life stages of Hellbenders (larvae, sub-adult, adult) to determine if an ontogenetic shift in microhabitat occurred in Little River. We found no significant differences in stream substrate at capture sites among the stages, but there was a positive correlation between rock shelters underlain with very coarse gravel and overall Hellbender occupancy. Although we found no difference in water quality parameters and streambed particle size among the stage classes at the sites of capture, there was a significant difference in the average shelter size among all stages, with larvae utilizing the smallest shelters. Based on these results, future Hellbender research and conservation efforts should consider differences in life stage habitat use as well as specific stream particle classes.