Spatial Distribution of Black Bear Incident Reports in Michigan

Evaluating density-weighted connectivity of black bears (Ursus americanus) in Glacier National Park with spatial capture-recapture models

BACKGROUND

Improved understanding of wildlife population connectivity among protected area networks can support effective planning for the persistence of wildlife populations in the face of land use and climate change. Common approaches to estimating connectivity often rely on small samples of individuals without considering the spatial structure of populations, leading to limited understanding of how individual movement links to demography and population connectivity. Recently developed spatial capture-recapture (SCR) models provide a framework to formally connect inference about individual movement, connectivity, and population density, but few studies have applied this approach to empirical data to support connectivity planning.

METHODS

We used mark-recapture data collected from 924 genetic detections of 598 American black bears (Ursus americanus) in 2004 with SCR ecological distance models to simultaneously estimate density, landscape resistance to movement, and population connectivity in Glacier National Park northwest Montana, USA. We estimated density and movement parameters separately for males and females and used model estimates to calculate predicted density-weighted connectivity surfaces.

RESULTS

Model results indicated that landscape structure influences black bear density and space use in Glacier. The mean density estimate was 16.08 bears/100 km2 (95% CI 12.52-20.6) for females and 9.27 bears/100 km2 (95% CI 7.70-11.14) for males. Density increased with forest cover for both sexes. For male black bears, density decreased at higher grizzly bear (Ursus arctos) densities. Drainages, valley bottoms, and riparian vegetation decreased estimates of landscape resistance to movement for male and female bears. For males, forest cover also decreased estimated resistance to movement, but a transportation corridor bisecting the study area strongly increased resistance to movement presenting a barrier to connectivity.

CONCLUSIONS

Density-weighed connectivity surfaces highlighted areas important for population connectivity that were distinct from areas with high potential connectivity. For black bears in Glacier and surrounding landscapes, consideration of both vegetation and valley topography could inform the placement of underpasses along the transportation corridor in areas characterized by both high population density and potential connectivity. Our study demonstrates that the SCR ecological distance model can provide biologically realistic, spatially explicit predictions to support movement connectivity planning across large landscapes.

Factors influencing frequency and severity of human-American black bear conflicts in New York, USA

Free-ranging large carnivores are involved in human-wildlife conflicts which can result in economic costs. Understanding factors that lead to human-wildlife conflicts is important to mitigate these negative effects and facilitate human-carnivore coexistence. We used a human-American black bear (Ursus americanus) conflict database maintained by the New York State Department of Environmental Conservation to determine whether drought, conflicts within the Adirondack and Catskill Parks as compared to outside of these parks, mild severity (Class 3) conflicts early in the year (April-June), and bear harvest in the previous year (as an index of bear abundance), were associated with greater frequency of high or moderate severity (Class 1-2) conflicts later in the year (July-September) across New York, USA. During 2006-2019, we obtained 3,782 mild severity conflict records early in the year, and 1,042 high or moderate severity records later in the year. We found that a one standard deviation increase in the cumulative precipitation difference from mean early in the year (about 7.59 cm) coincided with a 20% decrease in conflicts, and that Wildlife Management Units (WMUs) within the parks were predicted to have 5.61 times as many high or moderate severity conflicts as WMUs outside the parks. We also found that a one standard deviation increase in the frequency of mild severity conflicts (equivalent to 5.68 conflicts) early in the year coincided with an increase in the frequency of high or moderate severity conflicts in a WMU later in the year by 49%, while a one standard deviation increase in the bear abundance index in the previous year (0.14 bears/10 km2) coincided with a 23% increase in high or moderate severity conflicts. To reduce the frequency and severity of conflicts to facilitate human-black bear coexistence, we recommend the following measures to be taken in place consistently and build over time in local communities: (i) further reducing black bear access to anthropogenic foods and other attractants, (ii) non-lethal measures including bear-resistant waste management, (iii) electric fencing, and (iv) modifying placement or configuration of field crops.

Human recreation impacts seasonal activity and occupancy of American black bears (Ursus americanus) across the anthropogenic-wildland interface

Protected areas serve an important role in wildlife conservation, yet most wildlife occur outside these areas, subject to varying degrees of human disturbance. In the Upper Peninsula of Michigan, American black bears (Ursus americanus), a highly mobile, opportunistic species, are common despite an extensive outdoor recreation industry with the potential to affect black bear spatial and temporal activity. We investigated how environmental and anthropogenic factors influence black bear occupancy, detection, and diel activity patterns across the anthropogenic-wildland interface before and after hibernation. Using 30 camera traps deployed across a rural-wildland interface, we captured black bears at 23 camera sites (~ 77%), which exhibited co-occurrence with humans at 10 sites (~ 33%), revealing that human presence and human population density exert negative effects on black bear seasonal occupancy. Bears were more nocturnal during the hunting season, before hibernation. Human recreational activity increased ~ 38% after hibernation, but bear diurnal activity also increased ~ 36%, except when cubs were present. Our results suggest bears prioritize avoiding humans spatially, rather than temporally, except during the hunting season and when cubs are present. Understanding black bear responses to human recreation patterns and environmental variation is essential for minimizing human-mediated disturbance, and fueling conservation efforts of large, charismatic carnivores.

Patterns of Human–Brown Bear Conflict in the Urban Area of Brașov, Romania

Human–bear conflicts are increasing in number due to deforestation, urban expansion, tourism, and habitat invasion by humans. Our study was conducted in Brașov, a picturesque city in central Romania. Brașov is surrounded by forests and has significant tourist traffic, but also much uncollected garbage and many garbage containers, which attract brown bears. We recorded human–bear conflicts in four districts (Răcădău, the Historic Centre, Noua, and Gară) between 2004 and 2018, finding 55 cases in total, of which in 19 cases involving people, 4 people were killed and 32 were injured. In 36 cases, there were no human victims. We mapped the locations of human–bear conflicts and garbage containers, then analysed their space–time location and human victims in terms of behavioural factors. The altitudes at which brown bears were identified ranged from 580 to 790 m, whereas bears were found in the city at distances of between 100 and 2600 m from the forest. The highest frequency of human–bear conflicts occurred during summer and autumn, and the most common behavioural factor was human outdoor activities. This study provides an important background for understanding human–bear conflicts and will help local authorities develop effective strategies to reduce human–bear conflicts and mitigate risk.

Spatial genetic structure and landscape connectivity in black bears: Investigating the significance of using different land cover datasets and classifications in landscape genetics analyses

Landscape genetic analyses allow detection of fine-scale spatial genetic structure (SGS) and quantification of effects of landscape features on gene flow and connectivity. Typically, analyses require generation of resistance surfaces. These surfaces characteristically take the form of a grid with cells that are coded to represent the degree to which landscape or environmental features promote or inhibit animal movement. How accurately resistance surfaces predict association between the landscape and movement is determined in large part by (a) the landscape features used, (b) the resistance values assigned to features, and (c) how accurately resistance surfaces represent landscape permeability. Our objective was to evaluate the performance of resistance surfaces generated using two publicly available land cover datasets that varied in how accurately they represent the actual landscape. We genotyped 365 individuals from a large black bear population (Ursus americanus) in the Northern Lower Peninsula (NLP) of Michigan, USA at 12 microsatellite loci, and evaluated the relationship between gene flow and landscape features using two different land cover datasets. We investigated the relative importance of land cover classification and accuracy on landscape resistance model performance. We detected local spatial genetic structure in Michigan's NLP black bears and found roads and land cover were significantly correlated with genetic distance. We observed similarities in model performance when different land cover datasets were used despite 21% dissimilarity in classification between the two land cover datasets. However, we did find the performance of land cover models to predict genetic distance was dependent on the way the land cover was defined. Models in which land cover was finely defined (i.e., eight land cover classes) outperformed models where land cover was defined more coarsely (i.e., habitat/non-habitat or forest/non-forest). Our results show that landscape genetic researchers should carefully consider how land cover classification changes inference in landscape genetic studies.

Patterns of wild carnivore attacks on humans in urban areas

Attacks by wild carnivores on humans represent an increasing problem in urban areas across North America and their frequency is expected to rise following urban expansion towards carnivore habitats. Here, we analyzed records of carnivore attacks on humans in urban areas of the U.S. and Canada between 1980 and 2016 to analyze the general patterns of the attacks, as well as describe the landscape structure and, for those attacks occurring at night, the light conditions at the site of the attacks. We found that several behavioral and landscape-related factors were recurrent elements in the attacks recorded. The species for which the attack locations were available (coyote and black bear) attacked in areas with different conditions of landscape structure and artificial light. Specifically, black bears attacked more frequently in areas with abundant and aggregated vegetation cover and scarce buildings and roads, while coyotes attacked in a broader range of landscape conditions. At night, black bears attacked in generally darker areas than coyotes. By providing a comprehensive perspective of the phenomenon, this study will improve our understanding of how effective strategies aimed at reducing the frequency of risky encounters in urban areas should be developed.

Scale-dependent home range optimality for a solitary omnivore

Spatial and temporal heterogeneity are fundamental mechanisms structuring home ranges. Under optimality, an individual should structure their space use economically to maximize fitness. We evaluated support for three hypotheses related to range optimality in American black bears (Ursus americanus), predicting (a) range location on a landscape will correspond with high vegetation productivity, (b) increasing forest fragmentation will result in larger ranges, and (c) increasing proportion of forest and/or mean vegetation productivity will result in smaller ranges. We used black bear radio telemetry data from Michigan (2009-2015), Missouri (2010-2016), and Mississippi (2008-2017), USA. Annual space use excluded winter, and we separated seasonal space use into spring, summer, and fall. We collected data from 143 bears (80 females, 63 males), resulting in 97 annual and 538 seasonal ranges. We used generalized linear mixed models to evaluate productivity (estimated through Normalized Difference Vegetation Index [NDVI]) selection, and range size (km2) variation between individuals. At the annual scale, black bears consistently selected areas with greater vegetation productivity than the surrounding landscape; yet selection weakened and was more variable seasonally. Opposite to our prediction, we found that increasing fragmentation consistently resulted in smaller ranges; non-forested land covers and forest edges might provide greater abundance or more diverse foods for bears. Ranges with a greater proportion of forest were smaller, likely reflecting an increase in food and cover which could reduce movements, yet there was no support for more productive ranges also being smaller as expected from an area minimizing strategy. Black bears displayed a scale-dependent space use strategy: at larger spatial and temporal scales, productivity acted as the strongest limiting factor and energy maximizing was the dominant strategy, while an area minimizing strategy was exhibited seasonally. We revealed consistent, scale-dependent responses by black bears to environmental conditions, demonstrating the intrinsic plasticity of this adaptable omnivore.