Observations on habitat preference of juvenile eastern hellbender salamanders (Cryptobranchus alleganiensis)

Abstract

Laboratory experiments have provided a wealth of knowledge on antipredator responses and habitat preference in both terrestrial and aquatic salamanders, many of which are difficult to study under natural conditions. However, there remains a dearth of carefully designed experiments to elucidate habitat preferences of aquatic salamanders, many of which are of growing conservation concern. This experimental study evaluated shelter selection of nearly threatened larval eastern hellbender salamanders, Cryptobranchus alleganiensis, in North Carolina. We performed three experiments: 1) ability to burrow under 50% embedded cobble, 2) preference for cobble (~ 120–150 mm) versus gravel (~ 30–60 mm) in an aquarium (ex situ), and 3) preference for cobble over gravel in a natural stream setting (in situ). We found that salamanders (N = 11) showed a preference for cobble (~ 135–137 mm) in both aquarium and in-stream testing environments (87.7% and 88.5% of time, respectively) over gravel and burrowed under cobble in 95% of aquarium and in-stream trials. Moreover, salamanders were unable to burrow under 50% embedded cobble and were actively moving 38.1% of the time in our burrowing experiment, highlighting the potential for larvae to remain exposed to predators if streams contain buried substrate. Our study provides preliminary evidence on the behavior of these cryptic larval salamanders, suggesting that they prefer cobble substrate and are unable to utilize embedded cobble. These findings have management implications for juveniles of this species, particularly in areas where prolonged sedimentation has the potential to make cobble unavailable for larvae.