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The conservation status of the 2 threatened grizzly bear (Ursus arctos) populations in the Cabinet-Yaak Ecosystem (CYE) of northern Montana and Idaho had remained unchanged since designation in 1975; however, the current demographic status of these populations was uncertain. No rigorous data on population density and distribution or analysis of recent population genetic structure were available to measure the effectiveness of conservation efforts. We used genetic detection data from hair corral, bear rub, and opportunistic sampling in traditional and spatial capture—recapture models to generate estimates of abundance and density of grizzly bears in the CYE. We calculated mean bear residency on our sampling grid from telemetry data using Huggins and Pledger models to estimate the average number of bears present and to correct our superpopulation estimates for lack of geographic closure. Estimated grizzly bear abundance (all sex and age classes) in the CYE in 2012 was 48–50 bears, approximately half the population recovery goal. Grizzly bear density in the CYE (4.3–4.5 grizzly bears/1,000 km2) was among the lowest of interior North American populations. The sizes of the Cabinet (n = 22–24) and Yaak (n = 18–22) populations were similar. Spatial models produced similar estimates of abundance and density with comparable precision without requiring radio-telemetry data to address assumptions of geographic closure. The 2 populations in the CYE were demographically and reproductively isolated from each other and the Cabinet population was highly inbred. With parentage analysis, we documented natural migrants to the Cabinet and Yaak populations by bears born to parents in the Selkirk and Northern Continental Divide populations. These events supported data from other sources suggesting that the expansion of neighboring populations may eventually help sustain the CYE populations. However, the small size, isolation, and inbreeding documented by this study demonstrate the need for comprehensive management designed to support CYE population growth and increased connectivity and gene flow with other populations. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

We present the first rigorous estimate of grizzly bear (Ursus arctos) population density and distribution in and around Glacier National Park (GNP), Montana, USA. We used genetic analysis to identify individual bears from hair samples collected via 2 concurrent sampling methods: 1) systematically distributed, baited, barbed-wire hair traps and 2) unbaited bear rub trees found along trails. We used Huggins closed mixture models in Program MARK to estimate total population size and developed a method to account for heterogeneity caused by unequal access to rub trees. We corrected our estimate for lack of geographic closure using a new method that utilizes information from radiocollared bears and the distribution of bears captured with DNA sampling. Adjusted for closure, the average number of grizzly bears in our study area was 240.7 (95% CI = 202–303) in 1998 and 240.6 (95% CI = 205–304) in 2000. Average grizzly bear density was 30 bears/1,000 km2, with 2.4 times more bears detected per hair trap inside than outside GNP. We provide baseline information important for managing one of the few remaining populations of grizzlies in the contiguous United States.

A fundamental challenge to estimating population size with mark-recapture methods is heterogeneous capture probabilities and subsequent bias of population estimates. Confronting this problem usually requires substantial sampling effort that can be difficult to achieve for some species, such as carnivores. We developed a methodology that uses two data sources to deal with heterogeneity and applied this to DNA mark-recapture data from grizzly bears (Ursus arctos). We improved population estimates by incorporating additional DNA \"captures\" of grizzly bears obtained by collecting hair from unbaited bear rub trees concurrently with baited, grid-based, hair snag sampling. We consider a Lincoln-Petersen estimator with hair snag captures as the initial session and rub tree captures as the recapture session and develop an estimator in program MARK that treats hair snag and rub tree samples as successive sessions. Using empirical data from a large-scale project in the greater Glacier National Park, Montana, USA, area and simulation modeling we evaluate these methods and compare the results to hair-snag-only estimates. Empirical results indicate that, compared with hair-snag-only data, the joint hair-snag-rub-tree methods produce similar but more precise estimates if capture and recapture rates are reasonably high for both methods. Simulation results suggest that estimators are potentially affected by correlation of capture probabilities between sample types in the presence of heterogeneity. Overall, closed population Huggins-Pledger estimators showed the highest precision and were most robust to sparse data, heterogeneity, and capture probability correlation among sampling types. Results also indicate that these estimators can be used when a segment of the population has zero capture probability for one of the methods. We propose that this general methodology may be useful for other species in which mark-recapture data are available from multiple sources.

We report the first abundance and density estimates for American black bears (Ursus americanus) in Glacier National Park (NP), Montana, USA. We used data from 2 independent and concurrent noninvasive genetic sampling methods—hair traps and bear rubs—collected during 2004 to generate individual black bear encounter histories for use in closed population mark–recapture models. We improved the precision of our abundance estimate by using noninvasive genetic detection events to develop individual-level covariates of sampling effort within the full and one-half mean maximum distance moved (MMDM) from each bear's estimated activity center to explain capture probability heterogeneity and inform our estimate of the effective sampling area. Models including the one-half MMDM covariate received overwhelming Akaike's Information Criterion support suggesting that buffering our study area by this distance would be more appropriate than no buffer or the full MMDM buffer for estimating the effectively sampled area and thereby density. Our model-averaged super-population abundance estimate was 603 (95% CI=522–684) black bears for Glacier NP. Our black bear density estimate (11.4 bears/100 km2, 95% CI=9.9–13.0) was consistent with published estimates for populations that are sympatric with grizzly bears (U. arctos) and without access to spawning salmonids.

Both black (Ursus americanus) and grizzly bears (U. arctos) are known to rub on trees and other objects, producing a network of repeatedly used and identifiable rub sites. In 2012, we used a resource selection function to evaluate hypothesized relationships between locations of 887 bear rubs in northwestern Montana, USA, and elevation, slope angle, density of open roads and distance from areas of heightened plant-productivity likely containing forage for bears. Slope and density of open roads were negatively correlated with rub presence. No other covariates were supported as explanatory variables. We also hypothesized that bear rubs would be more strongly associated with closed roads and developed trails than with game trails. The frequencies of bear rubs on 30 paired segments of developed tracks and game trails were not different. Our results suggest bear rubs may be associated with bear travel routes, and support their use as “random” sampling devices for non-invasive spatial capture–recapture population monitoring.

Non-invasive genetic sampling (NGS) methods have been instrumental in providing robust population abundance and density estimates of bears. We conducted a small pilot study to (1) evaluate 2 NGS methods of hair traps and bear rubs in the Russian Far East (RFE) on sympatric populations of Asiatic black bears (Ursus thibetanus) and brown bears (Ursus arctos), and (2) to identify potential DNA marker sets for future study. Genetic analysis required 6 microsatellite markers to definitively identify individuals plus a gender marker, and closed population models estimated 142 Asiatic black bears and 18 brown bears. Spatially-explicit mark–recapture (SECR) density estimates for brown bears were 3 bears/100 km2. Inflated Asiatic black bear estimates resulted from a lack of recaptures, although using combined detection data from the 2 NGS methods was found to improve precision for abundance estimates. Capture probabilities were higher for brown bears than for Asiatic black bears, but overall recapture probabilities were low for both species. The frequency of rubbing declined from June to August, possibly due to bears leaving the study area, and Asiatic black bears were detected less frequently on rubs than brown bears, suggesting that species-specific ecology must be incorporated into future study designs. We recommend that future applications of NGS in the RFE improve capture probabilities by sampling earlier in the season to mitigate geographic closure violation for abundance estimates and to increase the number of detections for robust spatially explicit capture–recapture analyses. Our results demonstrate that NGS methods have strong potential for monitoring of bear populations in the RFE.

Wildlife managers need reliable estimates of population size, trend, and distribution to make informed decisions about how to recover at-risk populations, yet obtaining these estimates is costly and often imprecise. The grizzly bear (Ursus arctos) population in northwestern Montana, USA, has been managed for recovery since being listed under the United States Endangered Species Act in 1975, yet no rigorous data were available to evaluate the program's success. We used encounter data from 379 grizzly bears identified through bear rub surveys to parameterize a series of Pradel model simulations in Program MARK to assess the ability of noninvasive genetic sampling to estimate population growth rates. We evaluated model performance in terms of 1) power to detect gender-specific and population-wide declines in population abundance, 2) precision and relative bias of growth rate estimates, and 3) sampling effort required to achieve 80% power to detect a decline within 10 years. Simulations indicated that ecosystem-wide, annual bear rub surveys would exceed 80% power to detect a 3% annual decline within 6 years. Robust-design models with 2 simulated surveys per year provided precise and unbiased annual estimates of trend, abundance, and apparent survival. Designs incorporating one survey per year require less sampling effort but only yield trend and apparent survival estimates. Our results suggest that systematic, annual bear rub surveys may provide a viable complement or alternative to telemetry-based methods for monitoring trends in grizzly bear populations.

Recent advances in genetic approaches have facilitated genetic marking in capture–recapture (CR) experiments. Individuals can now be identified through non-invasive sampling and multi-locus genotyping instead of physical capture. In non-invasive studies where collection sites are used, detection depends on whether (1) an individual deposits a sample at the collection site, and (2) an individual can be genetically identified from the sample. Here we evaluate factors influencing detection of grizzly bears (Ursus arctos) at hair-sampling sites from 4 genetic CR projects (2006–2012) in British Columbia, Canada, and provide recommendations for maximizing detection in future studies. We found significant effects of trap type (bait site vs. rub object), sex, and season on the detection of grizzly bears. Bait-site detection was approximately 5-fold greater than detection at rub objects; and bait sites generally detected the sexes equally, whereas rub-tree detection was strongly male-biased. At rub objects, males had a 7-fold greater detection during the breeding season compared with females. Genotyping success increased with the number of hair follicles in the sample and decreased with the duration between trap checks. Rainfall was correlated with trap duration and was also negatively related to genotyping success. Samples with little genetic material (<2 guard hair, or <15 underfur) had low genotyping success and are best avoided, especially if samples with more follicles exist. Rub objects are an efficient sampling method but we caution investigators that these traps, unless deployed in large numbers, imperfectly detect female bears. The combined effect of trap type, sex, and season on a bear visiting a site, paired with the effects of hair quality, quantity, and sampling duration or rainfall on genotyping success, produced a range of detection spanning 2 orders of magnitude, highlighting the imperative for investigators to consider these factors for CR projects.

We studied the marking behaviour of American black bears (Ursus americanus) during the breeding season 2013. Six remote video cameras captured 529 trapping nights. We collected behaviour, sex, and age class of bears rubbing on trees. Marking events (N = 31) were observed between 26 April and 27 July with a median of 12 June. The majority (96%) of marking events were performed diurnally. All bears we could accurately identify to sex were males (N = 16) and 29 of 31 marking bears were adults. The most frequent use of contact with substrate was bipedal marking followed by pede marking, quadrupedal marking. Bears used their back, neck, head, and cheeks in nearly 90% of observations while scratching and biting occurred in less than a third of observations. We documented the novel behaviour 'groin marking'. This study suggests rub trees are locations for chemical communication through a variety of marking techniques in forested environments.

To advance our knowledge on the rubbing behavior of Andean bears (Tremarctos ornatus), we assessed characteristics of their rub-trees in the Peruvian tropical dry forest, where water is a rare and critical resource. We registered characteristics of rubbed and unrubbed trees and shrubs along bear trails in an area of approximately 100 km2 surrounding 7 waterholes in the western Andes foothills of Peru during austral summer 2014–2015. Analysis of 94 trees selected for rubbing (hereafter, rub-trees) and 253 available unmarked trees within a 5-m radius of each rub-tree showed that bears selected trees to rub that were relatively small and close to waterholes. Bears seemed to avoid the most common tree species, palo santo (Bursera graveolens), for tree-rubbing. We suggest that waterholes are important habitat features for Andean bears in the Peruvian dry forest, and that these sites be incorporated into conservation and land use management.