Hair Snares Research Articles

Can hair snares provide a reliable method for estimating abundance of an exotic ungulate?

Mitigating exotic species invasions requires reliable information on abundance and source-sink dynamics to evaluate effectiveness of control efforts. Despite being present in the southeastern United States for centuries, wild pigs (Sus scrofa) continue to invade new areas, including the Sam D. Hamilton Noxubee National Wildlife Refuge (NNWR) in Mississippi, a forested landscape with an emerging wild pig population. Considering the early stage of invasion, we designed and implemented a non-invasive hair sampling technique to estimate abundance and relatedness of wild pigs within the NNWR. Following 8-week sampling periods in 2021 (n = 160 samples) and 2022 (n = 159 samples), we identified 38 and 26 unique individuals, respectively, although recapture rates were too low to yield precise abundance estimates. We also identified low heterozygosity indicating high relatedness among our population which likely reflected lack of barrier features to gene flow and/or a limited number of external source populations. Finally, we observed positive trends in viable samples collected relative to sampling week, suggesting more optimal sampling period(s) may exist (e.g., autumn). We also acknowledge that use of grain in more accessible areas rather than our remote approach using scent-only attractants may increase hair snare attractiveness and wild pig encounters, while permitting increased sampling frequency. Collectively, these modifications (i.e., altered season, bait type, and access) provide viable pathways to increase precision for abundance estimates. When used concomitantly with ongoing monitoring and control efforts, non-invasive hair sampling will contribute to a more holistic understanding of this exotic species and better inform management actions.

Community-led non-invasive polar bear monitoring in the Eeyou Marine Region of James Bay, Canada: insights on distribution and body condition during the ice-free season

Wildlife conservation is informed by detailed understanding of species demographics, habitat use, and interactions with environmental drivers. Challenges to collecting this information, particularly in remote places and on widely ranging species, can contribute to data deficiencies that detract from conservation status assessment and the effectiveness of management actions. Polar bears in James Bay face rapidly changing environmental conditions at the southern edge of their global range, but studying their ecology has been limited by community concerns about the methods typically used in polar bear research. Using a community-led and non-invasive approach, we deployed hair snare and camera trap sampling stations across 400 km of the Eeyou Marine Region in eastern James Bay. Stations collected >100 hair samples and thousands of photographs in one eight-week period that allowed for a novel investigation of this population’s distribution and body condition during the ice-free season. Polar bears were in average to above average body condition, and model selection of detections at stations revealed distance to mainland as a significant predictor of polar bear presence. Given its high potential, we suggest community-based monitoring using this method become a standard protocol to expand the scope and local leadership of polar bear research across the North.

Use of fecal DNA to estimate black bear density in an urban‐wildland interface

AbstractAmerican black bears (Ursus americanus) commonly habituate to human resources in regions of urban‐wildland interface, which frequently leads to human‐wildlife conflict. Monitoring bear densities is important to inform management, yet traditional density estimation methods may not be practical in such areas. Minimally or noninvasive genetic tools offer a potential solution, but the most common sampling method employs barbed‐wire hair snares and scented lure, which can pose dangers to people and pets. Fecal DNA, which is less invasive, has been used successfully for many species, but has not been commonly used for ursids in the United States. We conducted a pilot study from July–September 2018 to assess the feasibility of using fecal DNA in a spatial capture‐recapture analysis to estimate black bear density in the Lake Tahoe Basin in California, a region of high‐human density compared to other urban‐wildland interface localities in the United States, where bears pose significant nuisance problems. The use of fecal DNA allowed us to sample in both urban and wildland areas with minimal disturbance to the surrounding community. Based on 142 genotyped samples from 101 distinct individuals, we estimated an abundance of 0.84 bears/km2(95% CI = 0.58–1.21 bears/km2), which was similar to a previous capture‐recapture estimate in the study area and represents one of the highest densities reported for black bears. More generally, our findings indicated that fecal DNA capture‐recapture approaches provide a feasible means of estimating black bear densities in areas where hair sampling may be impractical.

Confirming the broadscale eradication success of nutria (Myocastor coypus) from the Delmarva Peninsula, USA

Nutria (Myocastor coypus) were introduced to the eastern shore of Chesapeake Bay, USA in the 1940s. They reached peak densities in the late 1990s, causing massive wetland loss. Beginning in 2002, a systematic plan to eradicate nutria from the 1.7M ha Delmarva Peninsula was implemented. Since that time the nutria population has been effectively reduced, and no nutria have been detected since May 2015. A lack of detection does not equate with complete absence. We address the following three questions. (1) What is the expected probability of nutria eradication from the Delmarva Peninsula as of the end of 2020? (2) If the probability of eradication is below the management target of 0.95, how much more surveillance is required? (3) How sensitive is the estimated probability of eradication to varying levels of public surveillance and modelled population growth rates? These questions were addressed by employing a stochastic spatially-explicit surveillance model that uses data in which no nutria were detected to quantify the probability of complete absence (PoA) over the entire Delmarva Peninsula. We applied an analytical framework that decomposes the spatial risk of survivors and data into management zones, and took advantage of low-cost public reporting of nutria sightings. Active surveillance by the eradication program included detector dog and tracker surveys, shoreline surveys, detection with ground and water platforms (with hair snares), and camera traps. Results showed that the PoA increased with time and surveillance from a beginning PoA in May 2015 of 0.01 to a mean of 0.75 at the end of 2020. This indicates that the PoA on the Delmarva was well below the target threshold of 0.95 for declaring eradication success. However, given continued surveillance without detection, a PoA of 0.95 would be achieved by June 2022. This analysis provides an objective mechanism to align the expectations of policy makers, managers and the public on when eradication of nutria from the entire Delmarva Peninsula should be declared successful.

Variable effects of wolves on niche breadth and density of intraguild competitors.

The parallel niche release hypothesis (PNR) indicates that reduced competition with dominant competitors results in greater density and niche breadth of subordinate competitors and which may support an adaptive advantage.We assessed support for the PNR by evaluating relationships between variation in niche breadth and intra‐ and interspecific density (an index of competition) of wolves (Canis lupus) coyotes (C. latrans), and bobcats (Lynx rufus).We estimated population density (wolf track surveys, coyote howl surveys, and bobcat hair snare surveys) and variability in space use (50% core autocorrelated kernel density home range estimators), temporal activity (hourly and overnight speed), and dietary (isotopic δ13C and δ15N) niche breadth of each species across three areas of varying wolf density in the Upper Peninsula of Michigan, USA, 2010–2019.Densities of wolves and coyotes were inversely related, and increased variability in space use, temporal activity, and dietary niche breadth of coyotes was associated with increased coyote density and decreased wolf density supporting the PNR. Variability in space use and temporal activity of wolves and dietary niche breadth of bobcats also increased with increased intraspecific density supporting the PNR.Through demonstrating decreased competition between wolves and coyotes and increased coyote niche breadth and density, our study provides multidimensional support for the PNR. Knowledge of the relationship between niche breadth and population density can inform our understanding of the role of competition in shaping the realized niche of species.

Novel hair snare and genetic methods for non-invasive bobcat detection.

Over the past 20 years, the use of non‐invasive hair snare surveys in wildlife research and management has become more prevalent. While these tools have been used to answer important research questions, these techniques often fail to gather information on elusive carnivores, such as bobcats (Lynx rufus). Due to the limited success of previous bobcat studies using hair snares which required active rubbing, this technique has largely fallen out of use, in favor of camera trapping. The goal of our study was to construct a novel, passive bobcat hair snare that could be deployed regardless of terrain or vegetation features, which would be effective for use in capture–recapture population estimation at a large spatial scale. This new hair snare was deployed in 1500 10‐km2 cells across West Virginia (USA) between two sampling seasons (2015–2016). Collected hair samples were analyzed with newly developed mitochondrial DNA primers specifically for felids and qPCR to determine species of origin, with enough sensitivity to identify samples as small as two bobcat hairs. Over the two years of the study, a total of 378 bobcat detections were recorded from 42,000 trap nights of sampling, for an overall rate of 0.9 detections/100 trap nights—nearly 2–6 times greater than any previous bobcat hair snare study. While the overall number of recaptured animals was low (n = 9), continued development of this platform should increase its usefulness in capture–recapture studies.

Density estimates for Canada lynx vary among estimation methods

AbstractUnbiased population density estimates are critical for ecological research and wildlife management but are often difficult to obtain. Researchers use a variety of sampling and statistical methods to generate estimates of density, but few studies have compared estimates across methods. During 2016–2017, we surveyed Canada lynx (Lynx canadensis) in southwestern Yukon Territory, Canada, using track transect counts, hair snares, camera traps, live traps, and Global Positioning System (GPS) collars. From these data, we estimated lynx density with two linearly scaled count methods, one spatial mark–recapture method, three spatial mark–resight methods, and one cumulative‐time method. We found up to fivefold variation in point density estimates despite adhering to method requirements and assumptions in a manner consistent with other studies. Our results highlight the dependency of density estimates on sampling process and model assumptions and demonstrate the value of careful and unbiased sampling design. Further research is needed to fully assess the accuracy and limitations of the many wildlife density estimation methods that are currently in use so that techniques can be appropriately applied to typical study systems and species.

Spatial correlation structures for detections of individuals in spatial capture-recapture models.

Spatial capture-recapture (SCR) models are commonly used to estimate animal density from surveys on which detectors passively detect animals without physical capture, for example, using camera traps, hair snares, or microphones. An individual is more likely to be recorded by detectors close to its activity center, the centroid of its movement throughout the survey. Existing models to account for this spatial heterogeneity in detection probabilities rely on an assumption of independence between detection records at different detectors conditional on the animals' activity centers, which are treated as latent variables. In this paper, we show that this conditional independence assumption may be violated due to the way animals move around the survey region and encounter detectors, such that additional spatial correlation is almost inevitable. We highlight the links between the well-studied issue of unmodeled temporal heterogeneity in nonspatial capture-recapture and this variety of unmodeled spatial heterogeneity in SCR, showing that the latter causes predictable bias in the same way as the former. We address this by introducing a latent detection field into the model, and illustrate the resulting approach with a simulation study and an application to a camera-trap survey of snow leopards Panthera uncia. Our method is a unifying model for several existing SCR approaches, with special cases including standard SCR, models that account for nonspatial individual heterogeneity, and models with overdispersed detection counts.

Fast, flexible alternatives to regular grid designs for spatial capture–recapture

Abstract Spatial capture–recapture (SCR) methods use the location of detectors (camera traps, hair snares and live‐capture traps) and the locations at which animals were detected (their spatial capture histories) to estimate animal density. Despite the often large expense and effort involved in placing detectors in a landscape, there has been relatively little work on how detectors should be located. A natural criterion is to place traps so as to maximize the precision of density estimators, but the lack of a closed‐form expression for precision has made optimizing this criterion computationally demanding. Recent results by Efford and Boulanger (2019) show that precision can be well approximated by a function of the expected number of detected individuals and expected number of recapture events, both of which can be evaluated at low computational cost. We use these results to develop a method for obtaining survey designs that optimize this approximate precision for SCR studies using count or binary proximity detectors, or multi‐catch traps. We show how the basic design protocol can be extended to incorporate spatially varying distributions of activity centres and animal detectability. We illustrate our approach by simulating from a camera trap study of snow leopards in Mongolia and comparing estimates from our designs to those generated by regular or optimized grid designs. Optimizing detector placement increased the number of detected individuals and recaptures, but this did not always lead to more precise density estimators due to less precise estimation of the effective sampling area. In most cases, the precision of density estimators was comparable to that obtained with grid designs, with improvement in some scenarios where approximate < 20% and density varied spatially. Designs generated using our approach are transparent and statistically grounded. They can be produced for survey regions of any shape, adapt to known information about animal density and detectability, and are potentially easier and less costly to implement. We recommend their use as good, flexible candidate designs for SCR surveys when reasonable knowledge of model parameters exists. We provide software for researchers to construct their own designs, in the form of updates to design functions in the r package oSCR.

American black bears and hair snares: a behavioral analysis

Despite the widespread use of noninvasive hair-sampling for American black bear (Ursus americanus) population monitoring, there is no explicit analysis of black bear behavior at hair snare sites. During 2016, we deployed hair snares and camera traps at 40 sites across the northern Lower Peninsula of Michigan, USA, and collected 560 video recordings of black bear activity. Our objectives were to develop an ethogram of bear behaviors at snare sites and quantify their occurrence. We found that bears allocated their time consistently when they were physically inside or outside of the snare, but they divided their time among multiple behaviors when crossing the wire. The inconsistencies in wire crossing revealed unexpected behaviors with important implications for study design. Our findings explicitly describe how black bears interact with hair snares, provide recommendations for addressing the influence of behavior on sampling efficiency, and establish a foundation for further study of animal behavior at hair snares.

Long-term use of non-invasive sampling methods: does successful sampling of brown bears by hair snares and camera traps change over time?

Abstract Context Non-invasive sampling methods are widely used by ecologists to collect animal hair, images, tissue or signs. Sampling devices are imperfect, and collection success may vary over time owing to behavioural changes in study organisms or other factors. If collection success decreases, the utility of non-invasive sampling devices for longitudinal studies that rely on consistency may be compromised. Aims Our primary objectives were to evaluate whether collection success of brown bear (Ursus arctos) hair by using hair snares and camera traps changed over time, and whether hair- and image-collection success was influenced by bear activity around the sampling site. Methods We paired non-invasive sampling by hair snares with motion-activated cameras at six streams in Alaska over 4–6 years, so as to evaluate how often brown bears left samples on wires or were photographed by cameras, and whether this sampling success changed over time. Changes in sampling success were evaluated in the context of bear activity per sampling period as determined by camera data (number of bear–wire encounters) or hair snare (number of barbs with hair); genetic analyses allowed us to evaluate whether the same bears were sampled repeatedly. Key results Overall, hair was collected in 78% and images in 73% of 2-day sampling periods when bears visited sites, and we observed no substantial change in the probability of successful sampling over time at 11 sites. The number of bear–wire encounters was positively correlated with the number of hair samples collected, as would be expected if sampling rates remained constant over time, and individual bears with previous wire experience were sampled in multiple years. Conclusions Overall, the results indicated that sampling success by using hair snare and camera trap showed substantial interannual variability, but changes over time were not consistently identified across sites. Among-site variation in sampling success highlighted the importance of accounting for site-specific differences in sampling success, and neither method sampled unfailingly. Implications Sampling by wires and cameras remained effective over time, suggesting that these non-invasive sampling methods may be successfully employed in long-term studies.

Alaskan brown bears (Ursus arctos) aggregate and display fidelity to foraging neighborhoods while preying on Pacific salmon along small streams.

The interaction between brown bears (Ursus arctos) and Pacific salmon (Oncorhynchus spp.) is important to the population dynamics of both species and a celebrated example of consumer‐mediated nutrient transport. Yet, much of the site‐specific information we have about the bears in this relationship comes from observations at a few highly visible but unrepresentative locations and a small number of radio‐telemetry studies. Consequently, our understanding of brown bear abundance and behavior at more cryptic locations where they commonly feed on salmon, including small spawning streams, remains limited. We employed a noninvasive genetic approach (barbed wire hair snares) over four summers (2012–2015) to document patterns of brown bear abundance and movement among six spawning streams for sockeye salmon, O. nerka, in southwestern Alaska. The streams were grouped into two trios on opposite sides of Lake Aleknagik. Thus, we predicted that most bears would forage within only one trio during the spawning season because of the energetic costs associated with swimming between them or traveling around the lake and show fidelity to particular trios across years because of the benefits of familiarity with local salmon dynamics and stream characteristics. Huggins closed‐capture models based on encounter histories from genotyped hair samples revealed that as many as 41 individuals visited single streams during the annual 6‐week sampling season. Bears also moved freely among trios of streams but rarely moved between these putative foraging neighborhoods, either during or between years. By implication, even small salmon spawning streams can serve as important resources for brown bears, and consistent use of stream neighborhoods by certain bears may play an important role in spatially structuring coastal bear populations. Our findings also underscore the efficacy of noninvasive hair snagging and genetic analysis for examining bear abundance and movements at relatively fine spatial and temporal scales.

Seeking efficiency with carnivore survey methods: A case study with elusive martens

ABSTRACTObtaining reliable information on species distributions is often the first step in conservation. Distribution information can be used to focus survey efforts to estimate population size and examine drivers of occupancy or other population parameters. We compared detection rates and survey costs for 2 techniques (remote cameras and scent detection teams) used to evaluate distribution of a rare carnivore, Humboldt subspecies of Pacific marten (Martes caurina humboldtensis). We used remote cameras at randomly placed sites in coastal Oregon, USA, to compare camera set type (baited, unbaited), bait height (<0.5 m, 1.37 m), and bait types (chicken and lure, cat food) for a 21‐day survey period during winter (27 Jan–12 Apr) and summer (04 Jul–14 Oct) 2015. When a marten was detected, we completed an additional survey within 25 m. Scent detection teams (human handler and dog) performed area‐constrained searches for scat deposited. We used a Bayesian occupancy model to compare detection probabilities for baited camera treatments. We detected martens at 26 sites, and offset stations detected martens at 15 of 24 sites (62.5%). Survey‐level detection probability for martens (the probability of detecting ≥1 marten during a survey) was high for the camera survey during summer and winter (estimates ranged from 60% to 99% and 33% to 82%, respectively), and similar for all treatments. We surveyed 50 sites with both remote cameras and scent detection teams 25 April–25 May 2015. Of 33 sites with ≥1 marten detection, 36.4% of units had a marten detected only by scent detection teams, 30.3% only by remote camera, and 33.3% by both techniques. When the objective was marten detection, survey costs were less for scent detection teams. For identifying individual martens and their sex, cameras paired with hair snares were more cost‐efficient. Scent detection teams provided a complementary method to baited remote cameras for assessing distribution. Using multiple techniques provided an opportunity to quantify limitations of survey methods. © 2018 The Wildlife Society.

Wildlife health indicators and mercury exposure: A case study of river otters (Lontra canadensis) in central British Columbia, Canada

Indicators of wildlife health are important elements of a comprehensive approach for assessing and monitoring trends of methyl mercury (MeHg) contamination in the environment. River otters (Lontra canadensis) have been used as a model species for toxicological studies on the effects of MeHg bioaccumulation due to their position as an apex predator in aquatic systems and sensitivity to environmental disturbance. Although laboratory studies suggest that sublethal MeHg exposure may have detrimental effects on wildlife, they are limited in their ability to reflect real world exposure and forecast population level effects. Few studies have identified the threshold at which MeHg exposure results in a population-level effect for wild populations of river otters in marine or fresh-water systems. We used a series of data sets collected over a 7-year period for river otter populations in central British Columbia, Canada, to assess mercury concentrations (river otter fur) and measurements of population status and health relative to a lake with an inactive and reclamated mercury mine along its shoreline (Pinchi Lake). We used a combination of remote cameras, marked individuals, hair snares, and scat counts/inventories to collect measurements of population status and health including: activity levels, population estimates, sex ratios, group sizes, litter sizes, behaviour, stress hormones, diet, and habitat quality. We found that mercury concentrations in river otter inhabiting Pinchi Lake were significantly higher than all other lakes in the study, and were also high relative to other areas in Canada and the United States. We did not, however, detect significant differences between the two lakes in many of the population parameters measured. We discuss the knowledge gaps and challenges of identifying the effects of MeHg for wild populations of mammals, determining sensitive and appropriate methods for measuring these effects, and the implications of our results for monitoring the impacts of natural resources activities. Detailed studies on population effects across a range of exposure and background conditions are required to address these data deficiencies. Typically, river otters are not included as monitoring species in environmental assessments even though their value as an indicator of anthropogenic contaminants has clearly been documented. We encourage inclusion of river otters in environmental assessments pre-, during -, and post-industrial activities as a measure of pollutant exposure and bioavailability as well as a critical first step in addressing knowledge gaps associated with contaminants and its effects on populations.

Noninvasive and cost‐effective trapping method for monitoring sensitive mammal populations

ABSTRACTNoninvasive sampling methods provide a means to monitor endangered, threatened, or sensitive species or populations while increasing the efficacy of personnel effort and time. We developed a monitoring protocol that utilizes single‐capture hair snares and analysis of morphological features of hair for evaluating populations. During 2015, we used the West Virginia northern flying squirrel (Glaucomys sabrinus fuscus) in the Monongahela National Forest, West Virginia, USA, to test the feasibility of using this protocol to sample a sensitive mammal species found at low densities in challenging terrain and inclement weather conditions. Our hair snare was successful in collecting hair from 316 squirrels of 3 species with 99.4% single captures and only 1 permanent capture. Using morphological analysis, we differentiated among northern flying squirrels, southern flying squirrels (G. volans), and red squirrels (Tamiasciurus hudsonicus) using 8 morphological measurements and an orthogonal discriminant function analysis to successfully refine and confirm identification of the hair. We advocate the use of this relatively noninvasive and inexpensive protocol for studying other sensitive wildlife species. © 2017 The Wildlife Society.

Winter bait stations as a multispecies survey tool.

Winter bait stations are becoming a commonly used technique for multispecies inventory and monitoring but a technical evaluation of their effectiveness is lacking. Bait stations have three components: carcass attractant, remote camera, and hair snare. Our 22,975 km2 mountainous study area was stratified with a 5 × 5 km sampling grid centered on northern Idaho and including portions of Washington, Montana, and British Columbia. From 2010–14, we conducted 563 sampling sessions at 497 bait stations in 453 5 × 5 km cells. We evaluated the effectiveness of cameras and hair snare DNA collection at stations to detect species and individual animals, factors affecting DNA viability, the effectiveness of re‐visiting stations, and the influence of elevation, seasonality, and latency on species detections. Cameras were more effective at detecting multiple species than DNA hair snaring. Length of deployment time and elevation increased genetic species ID success but individual ID success rates were increased only by collecting hairs earlier in the season. Re‐visiting stations did not change camera or genetic species detection results but did increase the number of individual genotypes identified. Marten and fisher were detected quickly while bobcat and coyote showed longer latency to detection. Seasonality significantly affected coyote and bobcat detections but not marten, fisher, or weasel. Multispecies bait station study design should incorporate mixed elevation sites with stratified seasonality. Priority should be given to including cameras as components of bait stations over hair snares, unless there is a specific genetic goal to the study. A hair snare component should be added, however, if individual ID or genetic data are necessary. Winter stations should be deployed a minimum of 45–60 days to allow for detection of low density species and species with long latency to detection times. Hair samples should be collected prior to DNA‐degrading late season rain events. Re‐visiting stations does not change which species are detected at stations; therefore, studies with objectives to delineate species presence or distribution will be more effective if they focus on deploying more stations across a broader landscape in lieu of surveying the same site multiple times.

Ski areas affect Pacific marten movement, habitat use, and density

ABSTRACTAlpine ski recreation is one of the most popular outdoor winter sports globally but often involves habitat modification and dense human activity, both of which can harm wildlife. We investigated the effects of ski area development and winter recreation activities on movement, occupancy, and density of Pacific martens (Martes caurina) in the Lake Tahoe region of California and Nevada, USA by comparing 3 ski and 3 control study areas. We systematically surveyed martens using live traps and hair snares during spring–summer and winter seasons from 2009 through 2011 to identify how martens responded to the year‐round effects of habitat fragmentation from ski area development and the seasonal effects of winter recreation activities. Martens selectively moved between remnant forest patches with the shortest crossing distances across open, non‐forested ski runs in both seasons, with the effect more pronounced in females. Overall, habitat connectivity was reduced by 41% in ski areas compared to habitat not fragmented by ski runs. During spring–summer, occupancy rates were not different between habitat within or outside of ski operations areas. During winter, however, occupancy was significantly lower inside (52%) ski area boundaries than outside (88%) them. Reduced detection probability in ski areas indicated martens also reduced the frequency of use of operations areas in winter. Using spatially explicit capture‐recapture models, we found that marten density did not differ between ski areas and controls during spring, but during winter female density declined at ski areas by 63% compared to spring–summer and was <50% of female density compared to controls. This suggests that females seasonally avoid habitat in ski areas by shifting their habitat use to areas outside ski operations boundaries during winter. Although male marten density did not differ, the lack of resident males >3 years old coupled with higher annual turnover rates suggests male densities at ski areas may be reliant on annual male immigration. In winter, martens avoided using habitat in ski operations areas when recreation activity was greatest. Winter ski recreation may not be incompatible with marten use of habitat in ski areas, but habitat fragmentation from ski areas affects marten movement and recreation activities affect seasonal habitat occupancy and female density. Maintaining functional habitat connectivity, via networks of short ski run crossings that link habitat in and out of ski areas, will be important for maintaining or improving marten use of remnant habitat in developed ski areas. © 2017 The Wildlife Society

Evaluating population expansion of black bears using spatial capture‐recapture

ABSTRACTThe population of American black bears (Ursus americanus) in southern New York, USA has been growing and expanding in range since the 1990s. This has motivated a need to anticipate future patterns of range expansion. We conducted a non‐invasive, genetic, spatial capture‐recapture (SCR) study to estimate black bear density and identify spatial patterns of population density that are potentially associated with range expansion. We collected hair samples in a 2,519‐km2 study area in southern New York with barbed‐wire hair snares and identified individuals and measured genetic diversity using 7 microsatellite loci and 1 sex‐linked marker. We estimated a mean density of black bears in the region of 13.7 bears/100 km2, and detected a slight latitudinal gradient in density consistent with the documented range expansion. However, elevation and the amounts of forest, crop, and developed landcover types did not influence density, suggesting that bears are using a diversity of resources in this heterogeneous landscape outside their previously described distribution. These results provide the first robust baseline estimates for population density and distribution associated with different landcover types in the expanded bear range. Further, genetic diversity was comparable to that of non‐expanding black bear populations in the eastern United States, and in combination with the latitudinal density gradient, suggest that the study area is not at the colonizing front of the range expansion. In addition, the diversity of landcover types used by bears in the study area implies a possible lack of constraints for further northern expansion of the black bear range. Our non‐invasive, genetic, spatial capture‐recapture approach has utility for studying populations of other species that may be expanding in range because SCR allows for the testing of explicit, spatial ecological hypotheses. © 2017 The Wildlife Society.

Examining the occupancy–density relationship for a low‐density carnivore

Summary The challenges associated with monitoring low‐density carnivores across large landscapes have limited the ability to implement and evaluate conservation and management strategies for such species. Non‐invasive sampling techniques and advanced statistical approaches have alleviated some of these challenges and can even allow for spatially explicit estimates of density, one of the most valuable wildlife monitoring tools. For some species, individual identification comes at no cost when unique attributes (e.g. pelage patterns) can be discerned with remote cameras, while other species require viable genetic material and expensive laboratory processing for individual assignment. Prohibitive costs may still force monitoring efforts to use species distribution or occupancy as a surrogate for density, which may not be appropriate under many conditions. Here, we used a large‐scale monitoring study of fisher Pekania pennanti to evaluate the effectiveness of occupancy as an approximation to density, particularly for informing harvest management decisions. We combined remote cameras with baited hair snares during 2013–2015 to sample across a 70 096‐km2 region of western New York, USA. We fit occupancy and Royle–Nichols models to species detection–non‐detection data collected by cameras, and spatial capture–recapture (SCR) models to individual encounter data obtained by genotyped hair samples. Variation in the state variables within 15‐km2 grid cells was modelled as a function of landscape attributes known to influence fisher distribution. We found a close relationship between grid cell estimates of fisher state variables from the models using detection–non‐detection data and those from the SCR model, likely due to informative spatial covariates across a large landscape extent and a grid cell resolution that worked well with the movement ecology of the species. Fisher occupancy and density were both positively associated with the proportion of coniferous‐mixed forest and negatively associated with road density. As a result, spatially explicit management recommendations for fisher were similar across models, though relative variation was dampened for the detection–non‐detection data. Synthesis and applications. Our work provides empirical evidence that models using detection–non‐detection data can make similar inferences regarding relative spatial variation of the focal population to models using more expensive individual encounters when the selected spatial grain approximates or is marginally smaller than home range size. When occupancy alone is chosen as a cost‐effective state variable for monitoring, simulation and sensitivity analyses should be used to understand how inferences from detection–non‐detection data will be affected by aspects of study design and species ecology.

Comparison of methods for estimating Amur tiger abundance

The Amur tiger Panthera tigris altaica is endangered throughout its range. Estimating abundance to monitor population trends is needed to judge success of conservation efforts. However, low densities and elusive behavior make precise estimates difficult to achieve. Managers must employ sampling methods that maximize precision while remaining feasible under constraints inherent to areas tigers inhabit. We applied camera trap, hair snare, DNA collection, scent‐matching dog, morphometric track identification and track survey methods and developed a rubric to evaluate their efficacy in estimating tiger abundance in Russia. We conducted sampling over the course of one year in Sikhote‐Alin Biosphere Zapovednik (SABZ). We ranked candidate methods using logistical, statistical and cost criteria to evaluate their efficacy for monitoring tiger numbers. Due to logistical and technical constraints, we relied on data from a parallel study to derive three statistical criteria for the DNA collection method. Camera traps, DNA collection, and track surveys were the only methods with sufficient sample sizes to estimate abundance for each sampling session during which the method was tested. DNA collection and camera traps were promising statistically, though poor‐performing for logistics and cost. Technical improvements in camera trap design since the time of this study may improve the method's statistical and cost performance compared to our evaluation. Conversely, track surveys were most efficient logistically and financially, but poor statistically. Method choice for any given monitoring situation should consider local conditions and the specific objectives of the monitoring program in light of all three criteria — statistical, logistical and cost. Failure in any of these areas can lead to failure of a monitoring program.