American Black Bears Ursus Americanus Research Articles

Pronounced brown bear aggregation along anadromous streams in interior Alaska

Aggregated use along salmon‐bearing (Oncorhynchus spp.) streams is common for coastal brown bears Ursus arctos; however, it is much less common in non‐coastal (interior) environments, especially in the Arctic. A concurrent study of GPS‐collared brown bears in the interior Brooks Range mountains, northern Alaska, revealed that salmon‐bearing streams and their use by brown bears were more prevalent than previously known. Our goal was to estimate the number, gender, and species of bears (Ursus spp.) using anadromous streams while salmon were present in an area of northern, interior Alaska. We deployed single‐catch breakaway hair snares on heavily‐used bear trails along 7 km sections of two anadromous streams to identify individual animals through DNA genotypes. We collected 119 hair samples from August and September in 2016 and 2017 which revealed 31 unique brown bears and five American black bears Ursus americanus across both streams. Using a capture‐with‐replacement analysis, we estimated 24 (95% CI: 22–27) brown bears used 7 km of one stream and 15 (95% CI: 9–35) brown bears used 7 km of the other. Across both streams, we detected a higher proportion of females than males, more brown bears than black bears, and greater relatedness among bears that used the same stream. The high number of brown bears estimated along these streams belies their overall low densities in the region, while relatedness patterns suggests that bears obtain behavioral specialization through social learning. A 354 km industrial road is permitted to be constructed along the southern flanks of the Brooks Range, bisecting numerous streams and rivers, including the two sampled above. Given our findings, we identify potential mitigation measures to reduce human‐bear conflicts related to aggregated brown bear use along anadromous streams.

Artificial night light helps account for observer bias in citizen science monitoring of an expanding large mammal population.

The integration of citizen scientists into ecological research is transforming how, where, and when data are collected, and expanding the potential scales of ecological studies. Citizen-science projects can provide numerous benefits for participants while educating and connecting professionals with lay audiences, potentially increasing the acceptance of conservation and management actions. However, for all the benefits, collection of citizen-science data is often biased towards areas that are easily accessible (e.g. developments and roadways), and thus data are usually affected by issues typical of opportunistic surveys (e.g. uneven sampling effort). These areas are usually illuminated by artificial light at night (ALAN), a dynamic sensory stimulus that alters the perceptual world for both humans and wildlife. Our goal was to test whether satellite-based measures of ALAN could improve our understanding of the detection process of citizen-scientist-reported sightings of a large mammal. We collected observations of American black bears Ursus americanus (n=1,315) outside their primary range in Minnesota, USA, as part of a study to gauge population expansion. Participants from the public provided sighting locations of bears on a website. We used an occupancy modelling framework to determine how well ALAN accounted for observer metrics compared to other commonly used metrics (e.g. housing density). Citizen scientists reported 17% of bear sightings were under artificially lit conditions and monthly ALAN estimates did the best job accounting for spatial bias in detection of all observations, based on AIC values and effect sizes ( =0.81, 0.71-0.90 95% CI). Bear detection increased with elevated illuminance; relative abundance was positively associated with natural cover, proximity to primary bear range and lower road density. Although the highest counts of bear sightings occurred in the highly illuminated suburbs of the Minneapolis-St. Paul metropolitan region, we estimated substantially higher bear abundance in another region with plentiful natural cover and low ALAN (up to ~375% increased predicted relative abundance) where observations were sparse. We demonstrate the importance of considering ALAN radiance when analysing citizen-scientist-collected data, and we highlight the ways that ALAN data provide a dynamic snapshot of human activity.

Response of female black bears to a high‐density road network and identification of long‐term road mitigation sites

AbstractRoads can result in negative effects on wildlife including habitat loss, behavioral avoidance, reduced survival, reproduction and gene flow. These road effects are especially pronounced for large mammals given their large home‐range requirements and low reproductive rates. To counteract these negative effects, road mitigation measures, such as underpasses and overpasses, are promoted; however, future landscape changes are rarely considered when selecting mitigation locations. We used GPS telemetry data on female American black bears Ursus americanus to examine their response to roads in Massachusetts, US. We compared bear road crossing frequency with a null crossing model derived from a correlated random walk, estimated road crossing movement speeds, and fit a road‐crossing resource selection function. We found that, though black bears crossed roads less than expected based on the null model, 10% of their observed steps, on average, crossed roads. We also found bears crossed roads at higher movement speeds than during other home‐range behaviors, and that bears preferred to cross smaller, less trafficked roads in areas with lower speed limits, less human development and more forest. We used the resource selection model to identify road segments for potential mitigation efforts and then used future human development projections to forecast future changes in these segments. We found a decrease of 15% in the length of suitable mitigation segments from 2019 to 2050. Given the sizeable investment in wildlife crossing structures and their longevity on the landscape, we recommend incorporating future projections into crossing site selection to ensure the long‐term viability of road mitigation efforts.

Regionalization of environmental and anthropic variables associated to livestock predation by large carnivores in Mexico

AbstractConflicts with humans are one of the main causes of the decline in populations of large carnivores, making it a crucial conservation issue worldwide. In Mexico, jaguar Panthera onca, puma Puma concolor and American black bear Ursus americanus are involved in livestock predation and are persecuted in retaliation. The sites where predation occurs are distributed throughout the country and differ not only in environmental characteristics, but also in social, economic and livestock management practices. However, due to the general focus of the studies carried out so far, the proposed mitigation measures are also general. It is necessary to consider conditions that encourage predation in the design of strategies to be more effective. In this study, environmental, anthropic and livestock management characteristics of livestock predation by large carnivores were analyzed for conflict regionalization. The variables most related to predation sites were identified, with a high percentage of them being livestock management practices. Based on these variables, we formed clusters of similar sites and analyzed their spatial distribution, which presented grouping patterns in the cases of predation by puma and black bear, in contrast to the jaguar clusters, which presented a dispersed distribution. Considering the characteristics of the clusters, we propose as mitigation measures the confinement of livestock, construction or improvement of corrals and improvement of management practices. The anthropic component and livestock management practices are closely related to the predation events and, therefore, their inclusion in the conservation programs of carnivores in Mexico is fundamental.

Genetic diversity, effective population size, and structure among black bear populations in the Lower Mississippi Alluvial Valley, USA

Multiple small populations of American black bears Ursus americanus, including the recently delisted Louisiana black bear subspecies U. a. luteolus, occupy a fragmented landscape in the Lower Mississippi Alluvial Valley, USA (LMAV). Populations include bears native to the LMAV, bears translocated from Minnesota during the 1960s, and recently reintroduced and colonizing populations sourced from within the LMAV. We estimated population structure, gene flow, and genetic parameters important to conservation of small populations using genotypes at 23 microsatellite markers for 265 bears from seven populations. We inferred five genetic clusters corresponding to the following populations: White River and western Mississippi, Tensas River and Three Rivers, Upper Atchafalaya, Lower Atchafalaya, and Minnesota. Upper Atchafalaya was suggested as the product of Minnesota-sourced translocations, but those populations have since diverged, likely because of a founder effect followed by genetic drift and isolation. An admixture zone recently developed in northeastern Louisiana and western Mississippi between migrants from White River and Tensas River, resulting in a Wahlund effect. However, gene flow among most populations has been limited and considerable genetic differentiation accumulated (global FST = 0.22), particularly among the three Louisiana black bear populations that existed when federal listing occurred. Consistent with previous bottlenecks, founder effects, and persisting isolation, all LMAV bear populations had low genetic diversity (AR = 2.08–4.81; HE = 0.36–0.63) or small effective population size (NE = 3–49). Translocating bears among populations as part of a regional genetic restoration program may help improve genetic diversity and increase effective population sizes.

Recreational harvest and incident‐response management reduce human–carnivore conflicts in an anthropogenic landscape

Summary Conserving viable large carnivore populations requires managing their interactions with humans in increasingly anthropogenic landscapes. Faced with declining budgets and escalating wildlife conflicts, agencies in North America continue to grapple with uncertainty surrounding the efficacy of socially divisive management actions such as harvest to reduce conflict. We used multistate capture–reencounter methods to estimate cause‐specific mortality for a large sample (>3500) of American black bears Ursus americanus in north‐western New Jersey, USA over a 33‐year period. Specifically, we focused on factors that might influence the probability of bears being harvested, lethally managed, or dying from other causes. We further analysed temporal correlations between >26 000 human–black bear incidents reported between 2001 and 2013 and estimates of total mortality rates, and specifically, rates of harvest from newly implemented public hunts and lethal management. Adult females were twice as likely (0·163 ± 0·014) as adult males (0·087 ± 0·012) to be harvested during the study period. Cubs (0·444 ± 0·025) and yearlings (0·372 ± 0·022) had a higher probability of dying from other causes, primarily vehicle strikes, than adults (0·199 ± 0·008). Reports of nuisance behaviours in year t + 1 declined with increasing mortality resulting from harvest plus lethal management in year t (P = 0·028, R2 = 0·338). Adult bears previously designated as a nuisance and/or threat were more likely to be harvested (0·176 ± 0·025) than those never identified as a problem (0·109 ± 0·010). Across age classes, individuals assigned problem status, were significantly more likely to be lethally controlled. Synthesis and applications. Given continuing failures in conserving exploited carnivores, their recreational harvest and lethal management remain polarizing. Within this social‐ecological system, the well‐regulated harvest of carefully monitored black bear populations represents a pragmatic approach to achieve population objectives. Furthermore, the integration of harvest and incident‐response management (both lethal and non‐lethal practices) with educational programmes aimed at reducing anthropogenic attractants can result in subsequent reductions in problem behaviours reported.

Sexual size dimorphism mediates effects of spatial resource variability on American black bear space use

AbstractThe distribution of animals is influenced by numerous factors including spatial distribution and temporal availability of resources. We tested the spatial resource variability hypothesis (increasing landscape heterogeneity results in increasing amount of space use) and the temporal resource variability hypothesis (temporal variation in resources reduces amount of space use) using location data from radiomarked American black bears Ursus americanus in Missouri and Arkansas, USA. We used 95% utilization distributions (UDs) to define individual seasonal space use and constructed 22 models using covariates that described composition, spatial arrangement and diversity of land cover types (an index of heterogeneity or patchiness); seasonal hard mast production; and seasonal use of land cover to test our hypotheses using linear modeling and small‐sample Akaike information criterion (AICc) model selection approaches. The AICc best performing model supported the spatial resource variability hypothesis and included Shannon diversity index [95% confidence limit (CL) of coefficient = 1.56–2.42] and sex (male; 95% CL of coefficient = 0.05–0.49) as covariates that explained variation in transformed values of UD size. Predicted and observed values during model evaluation were highly correlated (r = 0.90). As land cover heterogeneity increased, UD size increased, likely a consequence of bears responding to greater patchiness to maintain sufficient resources. Further, the Shannon diversity index was greater for males than females , suggesting larger bodied males used larger areas to meet their higher energetic costs due to landscape fragmentation. Studies of resource hypotheses in solitary species should consider intraspecific allometric relationships such as sexual size dimorphism as has been addressed using group size in social species.

Effects of Exposure on Genotyping Success Rates of Hair Samples from Brown and American Black Bears

Abstract Noninvasively collected hair samples have been used in numerous studies to answer questions about the demographic and genetic status and trends of wildlife populations. In particular, these methods are well-suited for researching and monitoring ursid populations, which are typically difficult to study because of their rare and cryptic nature. Recently, researchers have taken increasing advantage of natural bear behaviors to obtain hair samples for genetic analyses by conducting surveys of bear rubs (objects that bears rub against such as trees and power poles). The low quality and quantity DNA in noninvasively collected samples, however, can result in low genotyping success rates, which may be exacerbated by potentially lengthy duration of environmental exposure. We investigated the effects of environmental exposure (sunlight, moisture, and duration of exposure) on genotyping success rates of brown bear Ursus arctos and American black bear Ursus americanus hair samples. We exposed a total of 238 hair samples from one brown bear and one black bear to multiple treatments for either 30-d or 60-d, periods consistent with collection intervals of recent bear rub survey projects. Sample treatments consisted of full or dappled sunlight, kept dry or saturated with water one to two times daily. We genotyped each sample at three microsatellite loci commonly used in noninvasive genetic studies of bear populations. Our results were consistent with predictions, with all three factors significantly reducing genotyping success rates. Based on our results, we recommend that the specific conditions of field exposure be considered when selecting a suite of microsatellite markers for noninvasive genetic sampling projects, and that researchers carefully consider the duration and environmental conditions that hair samples will be exposed to when designing field studies. Limiting exposure to moisture and sunlight by collecting hairs from bear rubs at relatively short intervals and selecting dry and shaded sites should reduce DNA degradation and thus result in higher genotyping success rates.

A wavelet‐based approach to evaluate the roles of structural and functional landscape heterogeneity in animal space use at multiple scales

The functional relationship between habitat utilization and landscape spatial heterogeneity is fundamental to understanding the spatial nature of animal distribution across scales. Although structural and functional properties of landscape spatial heterogeneity can have different consequences for animal species, few studies have explicitly considered both forms of heterogeneity, partly due to the lack of general methods for direct assessment of scale‐specific associations between variables. We present a wavelet‐based approach to evaluate the roles of structural and functional landscape spatial heterogeneity in animal space use at multiple spatial scales. As a case study, we examined scale‐specific space use patterns of American black bears Ursus americanus in response to structural and functional spatial heterogeneity as well as spatial patterns of vegetation age‐classes in a Canadian boreal forest. We found strong differences in the effects of structural and functional spatial heterogeneity and the scales at which they are associated with the patterns of habitat use by black bears. Functional heterogeneity alone affected space use at 800 and 1600‐m scales, but had significant effects when interacting with structural heterogeneity at 400, 800, and 1600‐m scales. Compared with male bears, female black bears were most sensitive to patterns of forage abundance at intermediate scales, or more specifically, in young and regenerating forests that provide abundant soft mast in boreal forests. Our study highlights the importance of accounting for scale‐dependent properties of (structural and functional) spatial heterogeneity in assessing the ecological effects of landscape components and the effectiveness of the wavelet transform technique in identifying such scale‐specific relationships.

Density and distribution of a colonizing front of the American black bear Ursus americanus

AbstractEffective management of small expanding populations is aided by the availability of reliable estimates of distribution, as well as by demographic characteristics such as population density, genetic diversity and sex ratio. The range of the black bear Ursus americanus in the southeastern United States is expanding to include areas from which it has been extirpated for more than a century. Lack of baseline demographic data in recently reoccupied areas leaves little information on which to base emerging management needs. We estimated the current extent of expansion at the colonizing front of a black bear population in the central Appalachian Mountains and identified landscape‐scale habitat characteristics affecting the expansion. In 2007, we genotyped hair samples collected throughout a 8,205‐km2 area at six microsatellite loci to identify individual black bears and estimate genetic diversity. We used capture‐recapture and occupancy analyses to estimate density and distribution of black bears in our study area. Our results suggest that black bears were not uniformly distributed, but were localized to high elevations and protected public conservation lands. Limited availability of high elevations to the west, north and northeast of our study area may limit further expansion. Despite a limited distribution and low estimated population density (7.51 bears/100 km2), genetic diversity at genotyped loci was high (mean Ho = 0.81). Until the population grows further, the small number of individuals in the region may be sensitive to management practices that result in mortalities, especially to females. Our research exemplifies the utility of remote genetic sampling to estimate population demographics of wide‐ranging mammals throughout a large study area, particularly where private land ownership hinders intensive study.

Genomic analysis of expressed sequence tags in American black bear Ursus americanus

BackgroundSpecies of the bear family (Ursidae) are important organisms for research in molecular evolution, comparative physiology and conservation biology, but relatively little genetic sequence information is available for this group. Here we report the development and analyses of the first large scale Expressed Sequence Tag (EST) resource for the American black bear (Ursus americanus).ResultsComprehensive analyses of molecular functions, alternative splicing, and tissue-specific expression of 38,757 black bear EST sequences were conducted using the dog genome as a reference. We identified 18 genes, involved in functions such as lipid catabolism, cell cycle, and vesicle-mediated transport, that are showing rapid evolution in the bear lineage Three genes, Phospholamban (PLN), cysteine glycine-rich protein 3 (CSRP3) and Troponin I type 3 (TNNI3), are related to heart contraction, and defects in these genes in humans lead to heart disease. Two genes, biphenyl hydrolase-like (BPHL) and CSRP3, contain positively selected sites in bear. Global analysis of evolution rates of hibernation-related genes in bear showed that they are largely conserved and slowly evolving genes, rather than novel and fast-evolving genes.ConclusionWe provide a genomic resource for an important mammalian organism and our study sheds new light on the possible functions and evolution of bear genes.

Empirical comparison of density estimators for large carnivores

Summary 1. Population density is a critical ecological parameter informing effective wildlife management and conservation decisions. Density is often estimated by dividing capture–recapture (C–R) estimates of abundance () by size of the study area, but this relies on the assumption of geographic closure – a situation rarely achieved in studies of large carnivores. For geographically open populations is overestimated relative to the size of the study area because animals with only part of their home range on the study area are available for capture. This bias (‘edge effect’) is more severe when animals such as large carnivores range widely. To compensate for edge effect, a boundary strip around the trap array is commonly included when estimating the effective trap area (). Various methods for estimating the width of the boundary strip are proposed, but / estimates of large carnivore density are generally mistrusted unless concurrent telemetry data are available to define. Remote sampling by cameras or hair snags may reduce study costs and duration, yet without telemetry data inflated density estimates remain problematic. 2. We evaluated recently developed spatially explicit capture–recapture (SECR) models using data from a common large carnivore, the American black bear Ursus americanus, obtained by remote sampling of 11 geographically open populations. These models permit direct estimation of population density from C–R data without assuming geographic closure. We compared estimates derived using this approach to those derived using conventional approaches that estimate density as /. 3. Spatially explicit C–R estimates were 20–200% lower than densities estimated as /. AICc supported individual heterogeneity in capture probabilities and home range sizes. Variable home range size could not be accounted for when estimating density as /. 4. Synthesis and applications. We conclude that the higher densities estimated as / compared to estimates from SECR models are consistent with positive bias due to edge effects in the former. Inflated density estimates could lead to management decisions placing threatened or endangered large carnivores at greater risk. Such decisions could be avoided by estimating density by SECR when bias due to geographic closure violation cannot be minimized by study design.

Activity patterns of Asiatic black bears (Ursus thibetanus) in the Central Mountains of Taiwan

AbstractShifts in activity patterns and time budgets in response to environmental variables may yield insights into key factors affecting animal life histories. Activity data on wild Asiatic black bears Ursus thibetanus are limited, and non‐existent in tropical portions of their geographic range. During November 1998–November 2000, we monitored the activity (active vs. inactive) of bears within a national park in the tropics of central Taiwan. On the basis of 4630 readings from motion‐sensitive transmitters obtained in 24‐h monitoring sessions, bears were active 54–57% of the time over the course of the year. However, bears were more active during summer (60±15%sd) and fall (60±15%) than in spring (47±13%). They were active mainly during daylight hours in spring and summer, and also during fall when acorns, a principal fall food, were scarce. However, extensive nocturnal activity occurred in fall when acorns were abundant. Increased nocturnal activity in fall is consistent with studies of the related American black bear Ursus americanus, and suggests that this behavior is not necessarily driven by preparation for winter denning or because of disturbance by hunters (as posited in previous studies), as bears in our study did not den (except parturient females) and were not hunted or otherwise disturbed by people.

Seasonal Variation in American Black Bear Ursus americanus Activity Patterns: Quantification Via Remote Photography

Activity pattern plasticity may serve as an evolutionary adaptation to optimize fitness in an inconstant environment, however, quantifying patterns and demonstrating variation can be problematic. For American black bears Ursus americanus, wariness and habitat inaccessibility further complicate quantification. Radio telemetry has been the primary technique used to examine activity, however, interpretation error and limitation on numbers of animals available to monitor prevent extrapolation to unmarked or untransmittered members of the population. We used remote cameras to quantify black bear activity patterns and examined differences by season, sex and reproductive class in the Alleghany Mountains of western Virginia, USA. We used 1,533 pictures of black bears taken during 1998–2002 for our analyses. Black bears generally were diurnal in summer and nocturnal in autumn with a vespertine activity peak during both seasons. Bear‐hound training seasons occurred during September and may offer explanation for the observed shift towards nocturnal behaviour. We found no substantial differences in activity patterns between sex and reproductive classes. Use of remote cameras allowed us to efficiently sample larger numbers of individual animals and likely offered a better approximation of population‐level activity patterns than individual‐level, telemetry‐based methodologies.

Breeding behavior of the American black bear Ursus americanus

By means of videotape, we observed and timed courtship, mating, and refractoriness in the American black bear while confined in a semicaptive environment. Sixty-six courtships resulted in mating. During courtship, the male detected estrus and receptivity in the female. Courtship lasted 22.5±2.3 s (mean±S.E.M.). We videotaped and reviewed 61 matings that included mounts, pelvic thrusts, and flutters. Mating lasted 51.6±4.2 s. Within these 61 matings, there were 24 pelvic thrusts and 14 flutters observed. Pelvic thrusts averaged 2.3±0.3 times, while flutters averaged 11.1±2.9 times. Of the 61 courtship–mating segments, 28 segments depicted a male refractory period, while 27 segments depicted a female refractory period. The male refractory period lasted 44.9±6.1 s during which the male sat and licked his genital region. The female walked, ran away, or turned and attacked the male during her 54.2±8.3 s refractory period. This is the first time a large number of paired ursid matings has been described and timed.

Seasonal variation in stereotypic pacing in an American black bear Ursus americanus

The behaviour of a male American black bear Ursus americanus was observed for over 2400 h across all seasons of the year. Stereotypic pacing was most frequent, oriented away from the exhibit, and performed mainly after feeding during the period May–July; from August–November pacing was oriented towards the exhibit and performed mainly around feeding time. Placing bear odors in the enclosure slightly reduced pacing and increased exploring/foraging in the late spring. Hiding small food items in the exhibit almost completely eliminated pacing in the fall and replaced it with foraging. Comparison with seasonal changes in the behaviour of wild bears suggest that the stereotypy of this bear, and probably zoo bears in general, developed from two main primary behaviours that cannot be performed in a barren zoo environment: mate-seeking behaviour predominating in the late spring and foraging behaviour in the late summer and fall.