Efficient single‐survey estimation of carnivore density using fecal DNA and spatial capture‐recapture: a bobcat case study

Abstract

Population density estimates are necessary to inform management and conservation, yet are difficult to obtain for cryptic species such as carnivores, and often require intensive sampling. We implemented a single‐survey, closed session, scat sampling protocol to estimate bobcat density using fecal DNA and spatial capture‐recapture at two sites over five sessions in Virginia, USA. We employed a Poisson encounter model to allow for multiple detections on scat transect segments over a single collection interval, and compared single session and multistrata (closed, multi‐site, multisession) spatial capture‐recapture (SCR) approaches to estimate density for each site and session. We found improved precision for most estimates using the multistrata SCR approach, sharing data on baseline detection and individual movement across sites and sessions. We suggest the summer session estimates are representative of the resident population, that differences in density between summer and winter are representative of potential net recruitment, and that differences between consecutive summer sessions are representative of the net recruitment realized for the population (dependent on survival and emigration). Finally, we assessed factors affecting precision in single session model estimates and provide recommendations to improve detection and reduce credible intervals that may be applicable across the bobcat range and to other carnivore species. The single survey transect methodology provides flexibility in monitoring carnivore populations specifically, or as part of concurrent monitoring for multiple carnivore species. This methodology has potential to dramatically increase the effectiveness of conservation and management dollars, improving our ability to monitor carnivore populations and assess conservation needs and actions.

Space use and resource selection of bobcats in the Appalachian Mountains of western Virginia

“…and cougars ( Puma concolor ) remain extirpated from ecosystems in the Appalachian Mountains, leaving bobcats as an apex predator in the region, along with black bears ( Ursus americanus ) and coyotes ( Canis latrans ) [8]. Within this guild, bobcats are the only obligate carnivore, can occur at population densities approximately twice that of coyotes [9,10], and consume a diversity of taxa [8]. Thus, bobcats hold potential to influence populations of both prey and competitors, and understanding the spatial ecology of bobcats may be important to predicting spatial variation in top-down forces in these systems.…”

“…Existing information on bobcat spatial ecology in the region comes from studies conducted during the 1980s in Tennessee and Kentucky, both of which had sporadic monitoring associated with use of VHF telemetry and did not examine habitat selection [32,33]. Existing information on bobcat population and trophic ecology in Virginia comes from noninvasive genetic sampling and examination of stomach contents [9,10,34]. In the eastern portion of their range, most research into bobcat spatial ecology has been conducted in the Southeast and Northeast, yet these areas represent considerably different ecosystems than the central Appalachian Mountains.…”

Estimating density and detection of bobcats in fragmented midwestern landscapes using spatial capture–recapture data from camera traps

“…In Illinois, USA, forested landscapes have been reduced by 64% and currently characterized by young (<61‐year‐old) forests limited to the southern and western regions of the state (Crocker ). For these reasons, sound estimates of abundance are needed for monitoring the status of bobcat populations, detecting temporal changes in population trends, and promoting appropriate management decisions (Morin et al ).…”

“…Despite widespread distribution of bobcats throughout North America, estimates of abundance are limited and often constrained by the inability to make direct comparisons with previous studies because of nonstandardized methodologies and associated variability in sources of sampling bias (Thornton and Pekins , Morin et al ). Nevertheless, early attempts to estimate density of bobcats have relied primarily on techniques that lack measures of accuracy and precision, including indices of relative abundance such as trap‐nights per individual captured (Wood and Odum , Jenkins et al ), harvest (O’Brian and Boudreau ), snow‐tracking (Golden ), mail questionnaires (Anderson ), and scent‐station surveys (Linhart and Knowlton , Johnson and Pelton , Conner et al ); previous studies have identified sex‐ and age‐specific biases in each of these methods (Diefenbach et al ).…”

Evaluating and integrating spatial capture-recapture models with data of variable individual identifiability

“…SCR models are well-suited for noninvasive genetic sampling in which individuals are uniquely identified, typically using DNA from feces or hair samples, to produce fully-observable encounter histories (Gardner et al 2009, Kery et al 2011, Morin et al 2016, 2018). Scat-detection dogs in particular have become a common tool to efficiently collect feces on large landscapes within a narrow time window to ensure demographic closure even for species that occur at low densities (Wasser et al 2004, 2011).…”