Eastern massasauga demography and extinction risk under prescribed‐fire scenarios

Abstract

ABSTRACTThe use of poorly estimated or surrogate population parameter estimates to assess population viability may result in misleading predictions. Consequently, a critical first step to understanding population health and the effects of land management practices on threatened species is estimation of site‐specific demographic parameters. A major threat to the eastern massasauga (Sistrurus catenatus) is habitat loss due to encroachment of woody vegetation and invasive species. Current land management practices require periodic burning or mowing to maintain habitat suitability. Although these methods improve habitat quality, they may also increase the risk of depredation due to reduced ground cover if burns are too extensive or cause mortality if conducted when snakes are active. We fitted contemporary capture–recapture and matrix models to an 8‐year dataset to estimate population parameters for an eastern massasauga population near the range center of the species, where the largest number of eastern massasauga populations may still persist. From 2009 to 2016, we captured 826 eastern massasaugas 1,776 times. In general, annual survival increased with increasing age (age 0 = 0.38, age 1 = 0.65, age 2 = 0.67, age ≥3 females = 0.71, age ≥3 males = 0.66). Abundance estimates ranged from 84 to 140 adults and annual reproductive frequency was 0.44 (95% CI = 0.29–0.59). We simulated increased mortality due to prescribed burns during spring, fall, and late fall for 50 and 100 years. The baseline model, which incorporated current prescribed‐fire practices, indicated a stable population with only a 0.2–0.6% probability of extinction over 100 years, suggesting that management practices at this site are sustainable if they remain unchanged. Simulations of conservative increases in mortality due to fire changed the probability of extinction little over 50 years (≤0.7%) but increased probability of extinction up to 24.5% over 100 years in the most pessimistic prescribed‐burn scenario. These prescribed‐burn simulations may be comparable to burn regimes used at other eastern massasauga sites. The population parameters estimated here provide information needed for assessing range‐wide population viability and investigating geographic variation in eastern massasauga demography. © 2018 The Wildlife Society.