Detecting long‐term population trends for an elusive reptile species

Abstract

Many reptile species are in decline and turtles are especially susceptible. In Massachusetts, eastern box turtle (Terrapene carolina carolina) population densities are critically low, and they are listed as a Species of Special Concern. To aid in the conservation of this species, we developed a statewide population monitoring program to track large‐scale population trends. We used GENPRES3 to identify the most efficient sampling design a priori. Using this design, we performed visual surveys in 2010–2012 and used site occupancy models to evaluate baseline occupancy and abundance data. We surveyed 62 4‐ha monitoring plots within early successional and forest edge habitat where box turtles congregate in the spring for foraging, mating, nesting, and thermoregulation. We also used radio‐telemetry at 2 survey sites to evaluate assumptions and further assess occupancy rates, detection estimates, and population size. The best fit Royle–Nichols model predicted a probability of box turtle occupancy of 0.81 ± 0.10 (mean ± SE) and a mean probability of detection of 0.29 ± 0.18. Roads and vegetation density were important covariates affecting the probability of occurrence. Survey start time, humidity, and surveyor were important covariates affecting detection probability. A power analysis indicated that we could detect a 10% decline in occupancy between 5‐year sampling rounds within 15 years. The proportion of radio‐tagged turtles inside the survey plots during surveys was relatively constant at each site (0.44–0.63 and 0.36–0.43), mean detection rate was 0.35 ± 0.10, and the total estimated population size of the 2 survey plots (8 ha total) was 13.31 ± 1.53. Our results can be used to track the status of this rare species as well as guide conservation actions and evaluate the effectiveness of site‐specific and statewide management plans. Our approach and design can serve as a model for other states developing monitoring programs for the eastern box turtle and other similar, rare and difficult to detect species. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Improving herpetological surveys in eastern North America using the environmental DNA method

“…Our results provide an empirical demonstration of the effectiveness of the eDNA method to efficiently characterize the presence of amphibians and reptiles in natural environments and show that eDNA may provide quantitative data comparable to measurements obtained by classical visual surveys. The extension or contraction of distribution ranges is one indicator of a species trend (Erb et al 2015;Mackenzie et al 2002;Zylstra et al 2010) and is a common indicator in recovery plan objectives (e.g., Environment Canada 2014). Environmental DNA can be used to define species range data from different habitats and merge sampling efforts when resources are limited.…”

“…Due to their ecology and life history traits, many amphibians and reptiles are very difficult to detect using classical monitoring methods (Bailey et al 2004a;Couturier et al 2013;Daigle and Jutras 2005;Lind et al 2005;Price et al 2012). To increase detection probability with practical efforts, surveys and monitoring programs are generally limited to a time window maximizing species detection (Erb et al 2015; Massachusetts Cooperative Fish and Wildlife Research Unit and the Northeast Wood Turtle Working Group 2013; Petitot et al 2014). Additionally, the time window optimizing species detection differs from one species to another, therefore, limiting the ability of developing simultaneous monitoring programs for the different species (Bailey et al 2004b;de Solla et al 2005;Pellet and Schmidt 2005).…”

Environmental DNA metabarcoding: Transforming how we survey animal and plant communities

“…Conventional physical methods can also cause destructive impacts on the environment and to biological communities (Wheeler, Raven, & Wilson, 2004), making them difficult to apply in a conservation context. Furthermore, when a species' behaviour or size makes it difficult to survey them (e.g., small-bodied or elusive species), conventional methods can require specialized equipment or species-specific observation times, thus making species richness and relative abundance estimates for entire communities intractable (e.g., many amphibians and reptiles, Erb, Willey, Johnson, Hines, & Cook, 2015;Price, Eskew, Cecala, Browne, & Dorcas, 2012). These reasons highlight the continued need to develop improved ways to survey global biodiversity, and the unique ways eDNA metabarcoding can complement conventional methods.…”

Species, causes, and outcomes of wildlife rehabilitation in New York State

“…In New York, box turtles are listed as a species of special concern [38,39]. Population estimates are not available for the species in New York State, likely due to the difficulty of surverying elusive and solitary reptiles, however successful surveys have been performed in neighboring states [40]. Impacts of roadway construction and an increasing density of vehicular traffic were exemplified in the large proportion of turtles presented following car collision.…”