Quantifying Uncertainty in Detection to Improve Monitoring Northeastern Populations of the Timber Rattlesnake (Crotalus horridus)
Abstract
In northern and high-elevation areas of the range of the Timber Rattlesnake (Crotalus horridus), each population depends on one to several communal hibernacula for overwintering. This ecological aspect of C. horridus has historically led to population declines and localized extirpations, as efforts to persecute the species have been concentrated on hibernacula while snakes congregated at the sites. Successful conservation of northeastern C. horridus populations depends on the protection of hibernacula and is contingent on understanding the distribution of the species. However, there are no published estimates of C. horridus detection probability to quantify uncertainty regarding its absence at sites of unknown occupancy. Using binomial mixed-effects models fitted to data from 97 surveys in Adirondack Park, New York, we estimated C. horridus detection probability as a function of air temperature, season, and mean encounter rate (number of snakes/survey hour). In the most parsimonious model, temperature was the sole explanatory covariate. For every 5.0 °C increase in temperature, detection odds increased by a factor of 6.18 (95% confidence interval = 3.12–23.95). Using the lower 95% confidence limit estimate of detection probability for the average survey temperature (22.0 °C), we found that four surveys at suspected hibernacula during egress or ingress periods were required to attain 99% confidence of absence. This model can be applied to understand the distribution of C. horridus populations in the Northeast and to calculate the number of repeat surveys required at a site before sufficient evidence of absence is attained.
Reference
David Rosenbaum; Christopher M. Schalk; Stacy A. McNulty. (2026). Quantifying Uncertainty in Detection to Improve Monitoring Northeastern Populations of the Timber Rattlesnake (Crotalus horridus). Journal of Herpetology. https://doi.org/10.1670/2912156
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