Wilde, Haley, Clean Water Institute, Lycoming College, 1 College Place, Williamsport, PA 17701, wilhale@lycoming.edu; Kaunert, Matthew, Clean Water Institute, Lycoming College, 1 College Place, Williamsport, PA 17701, kaunert@lycoming.edu.
The Eastern Hellbender (Cryptobranchus a. alleganiensis) represents an ancient lineage of giant (≤ 2.5 ft.), long-lived (> 25 years) stream-obligate salamanders endemic to the eastern United States. While considered indicators of stream habitat quality, hellbender populations have experienced rapid, range-wide declines driven by suppressed recruitment. Northwestern Pennsylvania has a long history of hellbender research, and stream systems in the region represent some of the highest quality habitat remaining throughout the hellbender’s range. Hillis and Bellis (1971) conducted demographic surveys in an Allegheny River tributary in 1968, providing one of the earliest assessments of Cryptobranchid ecology. Kaunert (2011) replicated these survey methods in 2010 and noted a decline in abundance within this historic population. In this study, we conducted mark-recapture surveys at the Hillis and Bellis (1971) site to evaluate long-term demographic trends for one of the longest monitored hellbender populations in existence. We conducted two traditional rock-lifting surveys in June – August 2024. We hand-captured individuals and measured total length (TL), snout-vent length (SVL), mass, and sex before permanently marking individuals with 12.5mm PIT-tags. We provide descriptive statistics to assess temporal trends in population size, density, sex ratio, and age/size class structure from 1968 – 2024. Overall, we recorded 27 capture events (n = 19 unique individuals) across two survey occasions in 2024. Population estimates declined from 1968 (152) to 2010 (89.60 ± 25.52) and 2024 (20.0 ± 2.5). While the proportion of old and young adults were comparable in 2010 and 2024, we failed to detect any sub-adults or juveniles within the population during this study. Male-skewed sex ratios were present in 1968 (1.58:1) and 2010 (2.47:1), but were even in 2024 (1:1). Temporal decreases in abundance and presence of young age classes are common signs of hellbender decline. However, given differences in sampling effort between historic and current monitoring efforts (9 vs. 2 surveys/year), more sampling is needed to compare population estimates. We will conduct additional mark-recapture surveys to improve sampling effort, increase accuracy of population estimates, and monitor demographic trends in this historic population in the coming years. Data from this project will be also be used to evaluate impacts of PennDOT bridge replacements within the watershed and estimate population persistence across Pennsylvania.
long term monitoring, hellbender, conservation