Water quality influences paternal care behaviors and nest fate in Eastern Hellbender salamanders

Abstract

Chronically suppressed recruitment via nest failure during egg development is the suspected demographic mechanism underpinning Eastern Hellbender salamander (Cryptobranchus a. alleganiensis) precipitous declines in North America. While Eastern Hellbenders exhibit unique paternal care behaviors during egg and larval stages, the relationship between water quality and reproductive behavioral ecology is poorly understood. In this study, we used artificial nest boxes and underwater video cameras to monitor nest success and investigate drivers of hellbender paternal care behaviors across a habitat quality gradient. We developed an ethogram using 237 h of video footage (54 video sessions) from 14 established hellbender nests between 2019 and 2021 in Pennsylvania and Ohio and found that nest abandonment contributes to nest failure in our system (5/14 nests). Ten nests hatched successfully and had a median hatching rate of 71% (range: 15–96%). Filial cannibalism occurred in most nests but did not cause nest failure. The proportion of time hellbenders cared for eggs (total care and total agitation) was positively affected by water temperature and conductivity. Overall, paternal care investment decreased with time since oviposition, particularly for total agitation. Fanning behaviors were not affected by environmental, biological, or temporal variables. Male size, body condition, and clutch size did not affect den master behaviors. Fanning behavior increased at higher conductivity levels in nest-attending male hellbenders, but not in nest-abandoning males. Overall, our results suggest that higher water temperatures and elevated conductivity levels may increase energy expenditure of guardian males and affect their ability to mitigate suboptimal conditions. In addition, the proportion of time invested in total care and fanning may serve as behavioral indicators of hellbender nest abandonment in high conductivity streams (>200 μS/cm).