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American 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. [ABSTRACT FROM AUTHOR]

From 2014–2019, 8 juvenile black bears (Ursus americanus) from different geographic regions were presented to the California Department of Fish and Wildlife because of emaciation, alopecia, and exfoliative dermatitis that resulted in death or euthanasia. Autopsy and histopathology revealed that all 8 bears had generalized hyperkeratotic dermatitis, folliculitis, and furunculosis. Skin structures were heavily colonized by fungal hyphae and arthrospores; fungal cultures of skin from 7 bears yielded Trichophyton equinum, a zoophilic dermatophyte reported only rarely in non-equid species. Additional skin conditions included mites (5), ticks (2), and coagulase-negative Staphylococcus sp. infections (2). No other causes of morbidity or mortality were identified. Molecular comparisons performed at the University of Texas Fungal Reference Laboratory determined that all isolates produced identical banding patterns, potentially representing a clonal population. Dermatophytosis is commonly localized and limited to the stratum corneum of the epidermis and hair follicles. Generalized disease with dermal involvement is rare in immunocompetent individuals; illness, malnutrition, age, or immunosuppression may increase susceptibility. Underlying causes for the severe disease impact in these bears were not evident after physical or postmortem examination. The mechanism by which bears from different geographic locations had severe, T. equinum –associated dermatophytosis from a potentially clonal dermatophyte could not be explained and warrants further investigation. [ABSTRACT FROM AUTHOR]

Silviculture was used to direct the development of young redwood stands toward old forest stand structures. Two variable-density thinning treatments and an unthinned control treatment were monitored for 10 years following treatment in young coast redwood (Sequoia sempervirens) stands in northern California, USA. The intent of these treatments was for forest restoration by accelerating the development of old forest features. The thinning treatments increased individual tree growth in both low and moderate density thinning treatments as compared to the control. The variable-density thinning also resulted in greater stand structural variability and was successful at increasing the relative proportion of redwood. Black bears (Ursus americanus) caused major damage to residual trees and showed a preference for more vigorous trees. Most of this damage occurred in the first four years after thinning. The confounding effects of thinning to favor larger trees and bear damage preferentially affecting more vigorous and large trees reduced the effectiveness of these treatments by eliminating the stems intended to form the future old forest structures. It also indicates forest managers need a conservative approach that leaves greater numbers of residual trees in redwood stands when bears are present. Thinning should leave sufficient trees to form the old forest structure plus ample allowances for bear-caused mortality. The long-term outcome of stand development in these thinned redwood forests is uncertain because of high rates of mortality in young trees. [ABSTRACT FROM AUTHOR]

We used genetic and stable isotope analysis of hair from free-ranging black bears ( Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human-bear management program. Specifically, we analyzed the isotopic composition of hair from bears known a priori to be food-conditioned or non-food-conditioned and used these data to predict whether bears with an unknown management status were food-conditioned (FC) or non-food-conditioned (NFC). We used a stable isotope mixing model to estimate the proportional contribution of natural foods (plants and animals) versus human food in the diets of FC bears. We then used results from both analyses to evaluate proactive (population-level) and reactive (individual-level) human-bear management, and discussed new metrics to evaluate the overall human-bear management program in Yosemite. Our results indicated that 19 out of 145 (13%) unknown bears sampled from 2005 to 2007 were food-conditioned. The proportion of human food in the diets of known FC bears likely declined from 2001-2003 to 2005-2007, suggesting proactive management was successful in reducing the amount of human food available to bears. In contrast, reactive management was not successful in changing the management status of known FC bears to NFC bears, or in reducing the contribution of human food to the diets of FC bears. Nine known FC bears were recaptured on 14 occasions from 2001 to 2007; all bears were classified as FC during subsequent recaptures, and human-bear management did not reduce the amount of human food in the diets of FC bears. Based on our results, we suggest Yosemite continue implementing proactive human-bear management, reevaluate reactive management, and consider removing problem bears (those involved in repeated bear incidents) from the population. © 2012 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Aversive conditioning (AC) has the potential to temporarily reduce conflicts between humans and black bears (Ursus americanus). From 2002 to 2005, I evaluated the effectiveness of projectiles with varying impact intensities, pepper spray, and chasing on approximately 150 bears in Sequoia National Park. Aversive conditioning was successful in keeping bears that were not food-conditioned from becoming food-conditioned. For the bears that were already food-conditioned, 17 of 29 bears subjected to AC abandoned unwanted behaviors, 6 required continual treatments, and 6 were killed or relocated. Success with food-conditioned bears was highest when AC was applied soon after bears obtained human food. Aversive conditioning was less successful on yearlings than adults. Rubber slugs were slightly more effective than lower impact projectiles. [ABSTRACT FROM AUTHOR]

The contemporary genetic structure of animal populations is sculpted by past events, including demographic bottlenecks and expansions and movement of animals by humans. In an analysis of microsatellite DNA of black bears (Ursus americanus; n = 540) across California, we discovered distinct population structure and genetic evidence of 2 historic colonization events. First, genotypes of bears sampled in southern California are most related to those from the Yosemite National Park region and not with spatially intervening populations. Historical records recount the translocation of 28 black bears from the Yosemite National Park area of the central Sierra Nevada to the San Bernardino Mountains in southern California in the 1930s. Second, before colonization of California by Europeans, the Central Coast region was inhabited by the now extinct California grizzly bear (Ursus arctos californiensis), but not black bears. Following an apparent competitive release and range expansion during the past century, black bears now inhabit the Central Coast region of California. Black bears in California's Central Coast display lower genetic diversity (founder effect) and a genetic signature most closely allied with black bears from the southern Sierra Nevada. In both these cases, molecular genetic techniques allowed historical reconstruction of anthropogenic events leading to changes in animal distributions. [ABSTRACT FROM AUTHOR]

Black bears (Ursus americanus) forage selectively in natural environments. To determine if bears also forage selectively for anthropogenic resources we analyzed data on vehicles broken into by bears from Yosemite National Park, California. We classified vehicles into 9 categories based on their make and model and collected data on use (2001-2007) and availability (2004-2005). From 2001 to 2007 bears broke into 908 vehicles at the following rates: minivan (26.0%), sport-utility vehicle (22.5%), small car (17.1%), sedan (13.7%), truck (11.9%), van (4.2%), sports car (1.7%), coupe (1.7%), and station wagon (1.4%). Only use of minivans (29%) during 2004-2005 was significantly higher than expected (7%). We discuss several competing hypotheses about why bears selected minivans. [ABSTRACT FROM AUTHOR]

The management of human American black bear (Ursus americanus) conflict has been of significant concern for Yosemite National Park (YNP) personnel since the 1920s. Park managers implemented the YNP Human Bear Management Plan in 1975 in an effort to reduce human bear conflicts, especially in the extensively developed Yosemite Valley (YV). We scat analysis to estimate annual and seasonal food habits of black bears in YV during 2001 We assessed the success of efforts to reduce the availability of anthropogenic foods, including garbage, by examining changes in the diet compared to a study from 1974 78 (Graber 1981). also quantified consumption of non-native fruit to address its possible contribution to human bear conflicts. The annual percent volume of human-provided food and garbage in black bear scats in YV decreased from 21% to 6% between 1978 and 2002, indicating YNP efforts have been effective. We found high use of non-native apples by bears throughout YV. Non-native food sources could be contributing to habituation and food conditioning, given their proximity to developed areas of YV. We recommend that YNP managers continue to (I) adapt and improve their management tools to address changing circumstances, (2) quantify the success new management tools, and (3) reduce the availability of non-native food sources. [ABSTRACT FROM AUTHOR]

The acquisition of behavior in animals is a function of both inheritance and learning, where learning can occur asocially (independent of other animals), socially (by observing other animals), or both. For species that have a prolonged parent-offspring relationship and that live solitary adult lives, social learning between parents and offspring may be a dominant form of learning. If parent-offspring learning is a dominant avenue for acquiring behavior or if behavior is inherited, then behaviors that confer significant fitness advantages should lead to subpopulations of genetically related individuals with similar behavioral patterns. We investigated whether food-conditioning behavior in black bears (Ursus americanus) is inherited or learned via parent-offspring social learning. We combined genetic data with behavioral data for 116 black bears from Lake Tahoe Basin, Nevada, and Yosemite National Park, California. We categorized individual bears as food-conditioned or non-food-conditioned based on their behavior over a several-year period of intensive study at each site. We compared levels of relatedness, based on microsatellite DNA genotyping, within and between these groups and compared behavior between 9 mother-offspring pairs determined through genetic analysis of maternity. Based on 4 separate analyses of the data there was little evidence that food-conditioning behavior in black bears partitioned along related lineages, indicating that the acquisition of food conditioning behavior was not solely a function of social learning or inheritance. [ABSTRACT FROM AUTHOR]

We developed and tested a system that alerts personnel when a radiocollared animal enters an area designated as off-limits. The remote alarm combines the monitoring capabilities of data loggers with a message transmitter that sends a voice message via 2-way radios when an animal enters a monitored area. We tested the remote alarm with food-conditioned American black bears (Ursus americanus) in Yosemite National Park by setting up 6 remote alarms in areas designated off-limits to bears (i.e., campgrounds and parking lots) and alternated nights when the message transmitters on the alarms were activated. We recorded the number of times a radiotagged bear entered an off-limits area, the number of times bear management detected a bear in areas off-limits, and the number of hazing events. Data loggers recorded 153 bear visits by 6 radiotagged bears, 59 with the alarm on and 94 with the alarm off. With the message transmitter activated, bear-managers found bears in areas off-limits 4 times more often than with the message transmitter off. Twelve hazing events occurred with the message transmitters active and 5 with them inactive. The number of bear visits/night to monitored areas was lower when message transmitters were active than when they were inactive, probably because bears entering areas off-limits were more likely to be detected and hazed with the message transmitter on. The remote alarm functioned well and aided park managers with their hazing program to reduce bear--human conflict. [ABSTRACT FROM AUTHOR]