Ursus Arctos Research Articles

Bear deterrence with scare devices, a non‐lethal tool in the use‐of‐force continuum

AbstractWild animals eating agricultural products and coming close to people's residences are primary causes of human–wildlife conflict worldwide. When carnivores eat anthropogenic foods and cause human safety concerns, it often results in the removal of the animals and public demand for reduced wildlife populations. The use of remote methods, such as scare devices, to deter carnivores has been touted in the literature; however, efficacy evidence remains thin. I test the efficacy of a widely available motion‐activated solar alarm lamp to deter grizzly bears (Ursus arctos) from farms in Montana, USA. When scare devices were activated, there was a 46% reduction in the odds bears would access an attractant. For every additional scare device, there was an additional 44% reduction in the odds of a bear getting the food. Additionally, scare devices caused bears to be more vigilant and increase movement behavior. More bears in a group led to loss of deterrence efficacy, and there was no evidence for habituation to the aversive stimuli. This deterrence method was most effective in August and for fungicide‐treated wheat. Out of 21 farms, scare devices stopped bears from returning to 11 sites. Overall, scare devices can be a cheap and easy first step to preventing, or resolving, some grizzly bear issues in the use‐of‐force continuum, which hierarchically organizes conflict responses from non‐lethal to more severe.

Does restoring apex predators to food webs restore ecosystems? Large carnivores in Yellowstone as a model system

AbstractModification of food webs is a frequent cause of shifts in ecosystem states that resist reversal when the food web is restored to its original condition. We used the restoration of the large carnivore guild including gray wolves (Canis lupis), cougars (Felis concolor), and grizzly bears (Ursus arctos horribilis) to the northern range of Yellowstone National Park as a model system to understand how ecosystems might resist reconfiguration after the restoration of apex predators to the food web. The absence of wolves, cougars, and grizzly bears for nearly a century from the northern range was the primary cause of dramatic changes in riparian plant communities. Willows (Salix spp.) were suppressed in height by intense browsing by the dominant herbivore, elk (Cervus canadensis). The loss of activity by beavers (Castor canadensis) coincided with the loss of tall willows. We hypothesized that intense elk browsing interrupted the mutualism between willow and beavers: ecosystem engineering by beavers was a critical component of willow habitat and tall willows were a critical component of habitat for beavers. This interruption made riparian communities resilient to the disturbance caused by the restoration of apex predators. We hypothesized further that reductions in elk browsing attributable to reductions in elk population size were not sufficient to prevent the suppression of willow growth. To test these hypotheses, we conducted a 20‐year, factorial experiment that crossed simulated beaver dams with the exclusion of browsing. We found that willows grew to heights expected for restored communities only in the presence of dams and reduced browsing. Willows experiencing ambient conditions remained well below this expectation. We found no difference in heights or growth rates of willows in experimental controls and willows in 21 randomly chosen sites, confirming that the results of the experiment were representative of range‐wide conditions. A reorganized community of large herbivores was implicated in the suppression of willow growth. We conclude that the restoration of large carnivores to the food web failed to restore riparian plant communities on Yellowstone's northern range, supporting the hypothesis that this ecosystem is in an alternative stable state caused primarily by the extirpation of apex predators during the early 20th century.

A Special Relationship—Aspects of Human–Animal Interaction in Birds of Prey, Brown Bears, Beavers, and Elk in Prehistoric Europe

Humans have developed a special relationship with some animal species throughout history, even though these animals were never domesticated. Based on raptors, bears, beavers, and elks, the question of whether there are similarities between the perception of these animals that triggered a special kind of fascination in humans and how the relationship between humans and these animals changed between Mesolithic age and medieval times is addressed. As we demonstrate, the categorical antagonism between ‘animal’ and ‘human’ is a concept that saw different kinds of influence, from the advent of sedentarism and husbandry to Christianity and from philosophical thinking in Classical Antiquity and the Period of Enlightenment. In prehistory and early history, we find different, opposing world views across time, cultures, and periods. Differences between animals and humans have been considered as fluid, and humans have had to engage with animals and their needs. The well-known and famous ‘bear ceremonies’ attested to different peoples and times were not unique, but were a part of belief systems that also included other animal species. Among the considered animals, certain raptor species attracted the attention of humans who tried to establish contact with them, as companions, whereas bears were almost ‘disguised humans’ due to all their similarities with humans, but they were also tabooed beings whose real names had to be avoided.

The origins and diversification of Holarctic brown bear populations inferred from genomes of past and present populations.

The brown bear (Ursus arctos) is one of the survivors of the Late Quaternary megafauna extinctions. However, despite being widely distributed across the Holarctic, brown bears have experienced extensive range reductions, and even extirpations in some geographical regions. Previous research efforts using genetic data have provided valuable insights into their evolutionary history. However, most studies have been limited to contemporary individuals or mitochondrial DNA, limiting insights into population processes that preceded the present. Here, we present genomic data from two Late Pleistocene brown bears from Honshu, Japan and eastern Siberia, and combine them with published contemporary and ancient genomes from across the Holarctic range of brown bears to investigate the evolutionary relationships among brown bear populations through time and space. By including genomic data from Late Pleistocene and Holocene individuals sampled outside the current distribution range, we uncover diversity not present in contemporary populations. Notably, although contemporary individuals display geographically structured populations most likely driven by isolation-by-distance, this pattern varies among the ancient samples across different regions. The inclusion of ancient brown bears in our analysis provides novel insights into the evolutionary history of brown bears and contributes to understanding the populations and diversity lost during the Late Quaternary.

Seed dispersal function of the brown bear Ursus arctos on Hokkaido Island in northern Japan: gut passage time, dispersal distance, germination, and effects of remaining pulp.

Megafauna are important seed dispersers because they can disperse large quantities of seeds over long distances. In Hokkaido, Japan, the largest terrestrial animal is the brown bear (Ursus arctos) and other megafauna seed dispersers are lacking. Thus, brown bears are expected to have an important function as seed dispersers in Hokkaido. In this study, we, for the first time, evaluated the seed dispersal function of brown bears in Hokkaido using three fleshy-fruited trees and studied: (1) gut passage time (GPT) in feeding experiments, (2) seed dispersal distance using tracking data of wild bears, and (3) the effect of gut passage and pulp removal on germination rate. Most seeds were defecated intact, and less than 6% were broken. The average GPT without pulp was 3h and 56min to 6h and 13min, depending on the plant and trial. Each plant's average simulated seed dispersal distance was 202-512m. The dispersal distance of Actinidia arguta seeds with pulp was significantly longer than those without pulp because of their longer GPT. The germination rate of defecated seeds without pulp was 19-51%, depending on the plant, and was significantly higher or not different comparing with that of seeds with pulp. We concluded that brown bears in Hokkaido are effective seed dispersers. In managing brown bears in Hokkaido, such ecological functions should be considered along with conserving the bear population and reducing human-bear conflicts.

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

BackgroundImproved 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.MethodsWe 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.ResultsModel 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.ConclusionsDensity-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.

Coupled social and ecological change drove the historical extinction of the California grizzly bear (Ursus arctos californicus).

Large carnivores (order Carnivora) are among the world's most threatened mammals due to a confluence of ecological and social forces that have unfolded over centuries. Combining specimens from natural history collections with documents from archival records, we reconstructed the factors surrounding the extinction of the California grizzly bear (Ursus arctos californicus), a once-abundant brown bear subspecies last seen in 1924. Historical documents portrayed California grizzlies as massive hypercarnivores that endangered public safety. Yet, morphological measurements on skulls and teeth generate smaller body size estimates in alignment with extant North American grizzly populations (approx. 200 kg). Stable isotope analysis (δ13C, δ15N) of pelts and bones (n = 57) revealed that grizzlies derived less than 10% of their nutrition from terrestrial animal sources and were therefore largely herbivorous for millennia prior to the first European arrival in this region in 1542. Later colonial land uses, beginning in 1769 with the Mission era, led grizzlies to moderately increase animal protein consumption (up to 26% of diet), but grizzlies still consumed far less livestock than otherwise claimed by contemporary accounts. We show how human activities can provoke short-term behavioural shifts, such as heightened levels of carnivory, that in turn can lead to exaggerated predation narratives and incentivize persecution, triggering rapid loss of an otherwise widespread and ecologically flexible animal.

Simultaneous estimation of the temporal and spatial extent of animal migration using step lengths and turning angles

BackgroundAnimals of many different species, trophic levels, and life history strategies migrate, and the improvement of animal tracking technology allows ecologists to collect increasing amounts of detailed data on these movements. Understanding when animals migrate is important for managing their populations, but is still difficult despite modelling advancements.MethodsWe designed a model that parametrically estimates the timing of migration from animal tracking data. Our model identifies the beginning and end of migratory movements as signaled by change-points in step length and turning angle distributions. To this end, we can also use the model to estimate how an animal’s movement changes when it begins migrating. In addition to a thorough simulation analysis, we tested our model on three datasets: migratory ferruginous hawks (Buteo regalis) in the Great Plains, barren-ground caribou (Rangifer tarandus groenlandicus) in northern Canada, and non-migratory brown bears (Ursus arctos) from the Canadian Arctic.ResultsOur simulation analysis suggests that our model is most useful for datasets where an increase in movement speed or directional autocorrelation is clearly detectable. We estimated the beginning and end of migration in caribou and hawks to the nearest day, while confirming a lack of migratory behaviour in the brown bears. In addition to estimating when caribou and ferruginous hawks migrated, our model also identified differences in how they migrated; ferruginous hawks achieved efficient migrations by drastically increasing their movement rates while caribou migration was achieved through significant increases in directional persistence.ConclusionsOur approach is applicable to many animal movement studies and includes parameters that can facilitate comparison between different species or datasets. We hope that rigorous assessment of migration metrics will aid understanding of both how and why animals move.

The synergistic impact of socioeconomic and landscape factors on spatial patterns of human-wildlife conflicts

With the expansion of human activities and increasingly effective protection of biodiversity, human-wildlife conflicts (HWCs) are increasing. Determining the patterns and causes of HWCs at the landscape scale is important for the design and implementation of effective management actions. We used in-house questionnaires, combined with data from insurance companies and other sources, to take the Tibetan Plateau as an example to reveal the pattern and potential causes of HWCs. Livestock predation and house break-ins were the most common types of conflict on the plateau, and wolves (Canis lupus) (56.9 %) and bears (Ursus arctos) (35.8 %) were the main culprits. In the pastoral zone, 65.3 % of conflicts were caused by wolves, more than in other regions, and bears accounted for 20.8 %. Bears were responsible for house break-ins in crop-dominated zones (60.5 %), while they preyed on livestock in mixed crop and pasture zones (80.0 %). Differences in forest cover between regions are likely to be the cause of this, with bears preying more on livestock in areas with greater forest cover. Livestock loss caused by wolves increased, and those caused by bears decreased, with increase in elevation. Households with more livestock experienced a greater incidence of HWCs. Livestock losses were lower in counties with higher gross regional product per capita, and economic development likewise influenced the occurrence of HWCs. Our research findings provide a fundamental understanding of the patterns of HWC, which can inform the development of evidence-based policies and strategies for effectively addressing HWCs in the future.

Times of trouble—seasonal variation in number and severity of attacks on sheep caused by large carnivores and eagles in Sweden

Wildlife managers and livestock owners can choose from a multitude of interventions to prevent carnivore attacks on domestic animals, ranging from light and sound deterrents to fencing and lethal control. To guide management and make the best and most cost-effective choice of interventions, knowledge about where and when these measures are needed the most is important. By identifying spatiotemporal patterns of carnivore attacks, resources can be used more efficiently to prevent such attacks. We used a Swedish nationwide, long-term data set to identify inter- and intra-seasonal variation in probability, number, and severity (number of killed or injured per attack) of large carnivore attacks on sheep. Our results show that there are specific “times of trouble”, regarding the number of attacks from golden eagle (Aquila chrysaetos) in late spring, and from brown bears (Ursus arctos), lynx (Lynx lynx), and wolves (Canis lupus) in late summer. Additionally, for brown bears and wolves, the severity of attacks varied throughout the grazing season with a peak in the latter part of the summer. The results can be used for guidance of temporal prioritisation of preventive interventions to reduce the probability, number, and severity of large carnivore attacks on sheep.

Testing foraging optimization models in brown bears: Time for a paradigm shift in nutritional ecology?

How organisms obtain energy to survive and reproduce is fundamental to ecology, yet researchers use theoretical concepts represented by simplified models to estimate diet and predict community interactions. Such simplistic models can sometimes limit our understanding of ecological principles. We used a polyphagous species with a wide distribution, the brown bear (Ursus arctos), to illustrate how disparate theoretical frameworks in ecology can affect conclusions regarding ecological communities. We used stable isotope measurements (δ13 C, δ15 N) from hairs of individually monitored bears in Sweden and Bayesian mixing models to estimate dietary proportions of ants, moose, and three berry species to compare with other brown bear populations. We also developed three hypotheses based on predominant foraging literature, and then compared predicted diets to field estimates. Our three models assumed (1) bears forage to optimize caloric efficiency (optimum foraging model), predicting bears predominately eat berries (~70% of diet) and opportunistically feed on moose (Alces alces) and ants (Formica spp. and Camponotus spp; ~15% each); (2) bears maximize meat intake (maximizing fitness model), predicting a diet of 35%-50% moose, followed by ants (~30%), and berries (~15%); (3) bears forage to optimize macronutrient balance (macronutrient model), predicting a diet of ~22% (dry weight) or 17% metabolizable energy from proteins, with the rest made up of carbohydrates and lipids (~49% and 29% dry matter or 53% and 30% metabolizable energy, respectively). Bears primarily consumed bilberries (Vaccinium myrtillus; 50%-55%), followed by lingonberries (V. vitis-idaea; 22%-30%), crowberries (Empetrum nigrum; 8%-15%), ants (5%-8%), and moose (3%-4%). Dry matter dietary protein was lower than predicted by the maximizing fitness model and the macronutrient balancing model, but protein made up a larger proportion of the metabolizable energy than predicted. While diets most closely resembled predictions from optimal foraging theory, none of the foraging hypotheses fully described the relationship between foraging and ecological niches in brown bears. Acknowledging and broadening models based on foraging theories is more likely to foster novel discoveries and insights into the role of polyphagous species in ecosystems and we encourage this approach.

Perceptions and attitudes of stakeholders on the return of brown bears (Ursus arctos): Contributions from a workshop held in northern Portugal

AbstractBrown bears (Ursus arctos) were extinct in Portugal by 1843. In the spring of 2019, a male bear was officially confirmed in northern Portugal, and more bears will likely reach the country shortly. We surveyed participants in a workshop held in Bragança in October 2021 to understand the perceptions and attitudes of different stakeholder groups (Administration, Research, Nongovernmental Organizations, and Local Stakeholders) regarding the return of brown bears to Portugal. Results indicate that, generally, participants would feel safe in areas where bears are present, are positive toward the return of brown bears, and see it as an opportunity for local development rather than a threat. Results also indicate a high level of consensus among groups of stakeholders concerning the issues analyzed. These preliminary results provide a baseline for perceptions and attitudes to consider when planning the conservation of brown bears returning to Portugal.

Individual genotypes from environmental DNA: Fingerprinting snow tracks of three large carnivore species.

Continued advancements in environmental DNA (eDNA) research have made it possible to access intraspecific variation from eDNA samples, opening new opportunities to expand non-invasive genetic studies of wildlife populations. However, the use of eDNA samples for individual genotyping, as typically performed in non-invasive genetics, still remains elusive. We present successful individual genotyping of eDNA obtained from snow tracks of three large carnivores: brown bear (Ursus arctos), European lynx (Lynx lynx) and wolf (Canis lupus). DNA was extracted using a protocol for isolating water eDNA and genotyped using amplicon sequencing of short tandem repeats (STR), and for brown bear a sex marker, on a high-throughput sequencing platform. Individual genotypes were obtained for all species, but genotyping performance differed among samples and species. The proportion of samples genotyped to individuals was higher for brown bear (5/7) and wolf (7/10) than for lynx (4/9), and locus genotyping success was greater for brown bear (0.88). The sex marker was typed in six out of seven brown bear samples. Results for three species show that reliable individual genotyping, including sex identification, is now possible from eDNA in snow tracks, underlining its vast potential to complement the non-invasive genetic methods used for wildlife. To fully leverage the application of snow track eDNA, improved understanding of the ideal species- and site-specific sampling conditions, as well as laboratory methods promoting genotyping success, is needed. This will also inform efforts to retrieve and type nuclear DNA from other eDNA samples, thereby advancing eDNA-based individual and population-level studies.

A retrospective study on the prevalence of main clinical findings in brown bears (Ursus arctos) rescued from substandard husbandry conditions.

Brown bears (Ursus arctos) are kept under varied captive conditions, some of which may greatly compromise their welfare. FOUR PAWS is an NGO that rescues some of these bears kept in substandard conditions and houses them in species-appropriate sanctuaries, where preventive and reactive veterinary care is provided. This retrospective study aims to provide an overview of pathologies and clinical abnormalities reported in veterinary records and their prevalence according to body system affected and pre-rescue bear origin. Origin was categorised as subzoo (bears coming from substandard zoos), dancing (used to "dance" upon a music cue), restaurant (used to attract clients), private keeping (used for various purposes, such as photo props), circus (used for shows), and bear-baiting (exploited for hunting dog training in baiting stations). Clinical findings were extracted from reports of veterinary examinations done from 2006 to 2021, during rescue, routinely, in response to clinical signs, and/or post-mortem. Their prevalence was calculated according to the body system affected and neoplasia (specific group independent from the organ) over the findings' total number. Prevalence was also calculated according to pre-rescue origin (general and relative values in proportion to the number of reports per origin). Results refer to 302 veterinary reports of 114 bears examined, rescued from 1998 to 2021, with the age at rescue varying from a few months to 30 years (median 13 years). The total number of clinical findings was 1,003, and the systems with more findings were oral cavity (56.0%), abdominal cavity and digestive system (7.9%), integumentary (7.9%), ocular systems (7.7%), and musculoskeletal (7.6%). Findings involving other body systems and neoplasia were less prevalent (≤2.8%). Results showed a higher prevalence of some clinical findings for bears rescued from certain origins compared to others. Straightforward associations between pre-rescue origin and clinical findings were not feasible due to unknown anamnesis and details on pre-rescue conditions, and because some housing and management characteristics might be transversal to origins. Results suggest that bears rescued from certain origins were prone to specific clinical findings, supporting the need for the creation of ad hoc preventive veterinary and husbandry management plans after rescue, thus contributing to the improvement of captive bear welfare.

Potential impacts of climate change on wild cherry distribution and associated consequences on brown bears

Wild cherry (Prunus avium) is a climate-sensitive species of great ecological importance and has gained importance in the diet of the Cantabrian brown bear (Ursus arctos L.) in recent years. Understanding the potential impact of climate change on the distribution of wild cherry and the interactions with bears, specially dispersion to more suitable areas under future climate change scenarios, may help to improve the conservation of both species in the Cantabrian Mountains (NW Spain). We accurately modelled the current and future habitat suitability for wild cherry, constructing species distribution models (SDMs) based on true presence and absence data and environmental variables related to the species ecological limitations. Associated effects were assessed by intersecting the current and future distributions of both species. Seed dispersal by bears was assessed by examination of bear faeces collected between 1995 and 2020. The findings are fundamental for developing forestry plans and strategies and enabling timely and appropriate evidence-based actions to be taken for conservation of both species. We found that the impact of climate change will decrease the overall habitat suitability, with more suitable areas expected to occur at higher elevations, where cherry consumption by bears and associated seed dispersal due to the spatial use may favour upward dispersal of cherry, although success and adaptation will ultimately depend on whether the seeds will be deposited in the right places and their movement will overcome the effects of climate change.

Research progress in pharmacological effectsand mechanism of Fel Ursi against cardiovascular and cerebrovascular diseases

Fel Ursi is a dried product obtained from the gallbladder of Ursidae animals, such as Selenarctos thibetanus or Ursus arctos, through gallbladder surgery for bile drainage. It is one of the rare animal medicinal materials in China and is known for its therapeutic effects, including clearing heat, removing toxins, extinguishing wind, relieving spasms, clearing the liver, and improving vision. Research has also found that Fel Ursi has pharmacological effects against cardiovascular and cerebrovascular diseases, such as anti-inflammatory, anti-apoptotic, and antioxidant stress properties. Recently, numerous studies have confirmed the close relationship between cardiovascular and cerebrovascular diseases and the gut microbiota as well as gut metabolites. Fel Ursi contains bile acid components that may have bidirectional regulatory effects on the gut microbiota and gut metabolites. This aspect could represent a potential therapeutic pathway for Fel Ursi in the treatment of cardiovascular and cerebrovascular diseases. This article comprehensively summarized relevant literature in China and abroad, reviewed the research progress on the pharmacological effects of Fel Ursi against cardiovascular and cerebrovascular diseases, and explored the impact of Fel Ursi on gut microbiota and gut metabolites, thereby aiming to provide references for further in-depth research and clinical application of Fel Ursi.

Proximity‐sensors on GPS collars reveal fine‐scale predator–prey behavior during a predation event: A case study from Scandinavia

AbstractAlthough the advent of high‐resolution GPS tracking technology has helped increase our understanding of individual and multispecies behavior in wildlife systems, detecting and recording direct interactions between free‐ranging animals remains difficult. In 2023, we deployed GPS collars equipped with proximity sensors (GPS proximity collars) on brown bears (Ursus arctos) and moose (Alces alces) as part of a multispecies interaction study in central Sweden. On 6 June, 2023, a collar on an adult female moose and a collar on an adult male bear triggered each other's UHF signal and started collecting fine‐scale GPS positioning data. The moose collar collected positions every 2 min for 89 min, and the bear collar collected positions every 1 min for 41 min. On 8 June, field personnel visited the site and found a female neonate moose carcass with clear indications of bear bite marks on the head and neck. During the predation event, the bear remained at the carcass while the moose moved back and forth, moving toward the carcass site about five times. The moose was observed via drone with two calves on 24 May and with only one remaining calf on 9 June. This case study describes, to the best of our knowledge, the first instance of a predation event between two free ranging, wild species recorded by GPS proximity collars. Both collars successfully triggered and switched to finer‐scaled GPS fix rates when the individuals were in close proximity, producing detailed movement data for both predator and prey during and after a predation event. We suggest that, combined with standard field methodology, GPS proximity collars placed on free‐ranging animals offer the ability for researchers to observe direct interactions between multiple individuals and species in the wild without the need for direct visual observation.

Contribution of hybridization between polar bears and grizzly bears to polar bear extinction

AbstractThis review explores whether recent hybridization events between polar bears (Ursus maritimus) and grizzly bears (Ursus arctos horribilis) will eventually contribute to the extinction of the modern polar bear. In April 2006, genetic analysis of an odd‐looking bear killed in the Northwest Territories, Canada, revealed this specimen to be a polar bear–grizzly bear hybrid, and additional hybrid bears were harvested beginning in April 2010. These events have been sensationalized by some in the media, who have speculated that the modern polar bear may become extinct due to crossbreeding with grizzly bears. Although studies support the introgression of brown bear genes into the polar bear genome during the Pleistocene, no evidence supports the occurrence of a similar event today. Even if such an introgression event occurred, hybrids evolving rapidly enough to adapt to ongoing sea ice depletion is not scientifically plausible. The loss of genetic integrity and modified morphology due to inbreeding between polar bears and grizzly bears are not considered threats to polar bear survival. As many scientists have stressed for decades, the greatest threat to the survival of the modern polar bear is sea ice depletion due to climate change.

Sex-Selective Infanticide and Sociality in Brown Bear Populations

Sex-Selective Infanticide and Sociality in Brown Bear Populations

An Ecoregional Conservation Assessment for Forests and Woodlands of the Mogollon Highlands Ecoregion, Northcentral Arizona and Southwestern New Mexico, USA

The Mogollon Highlands, Arizona/New Mexico, USA, spans a large biogeographical region of 11 biotic communities, 63 land cover types, and 7 ecoregions. This 11.3 M ha region has high levels of beta diversity across topo-edaphic gradients that span deserts to mountain tops. The main stressors affecting the region’s forests and woodlands include climate change, livestock grazing, and frequent mechanical removals of large amounts of forest biomass for fire concerns. We present an ecoregion conservation assessment for robust conservation area design that factors in appropriate wildfire response to protect communities from increasing threats of climate-induced wildfires spreading into urban areas. We focused mainly on maintaining connectivity for endangered focal species (grizzly bear (Ursus arctos horribilis) and Mexican wolf (Canis lupus baileyi)) along with protecting mature and old-growth (MOG) forests, Piñon (Pinus spp.)–Juniper (Juniperous spp.) Woodlands, and riparian areas. Over half the region is managed by federal agencies where new protected areas can be integrated with tribal co-management and prescribed burning, defensible space, and home hardening to protect communities from the growing threat of climate-induced wildfires. However, just 9% of the study area is currently protected, and even with the inclusion of proposed protected areas, only 24% would be protected, which is below 30 × 30 targets. The potential grizzly bear habitat, wolf habitat connectivity, and MOG forests (1.6 M ha (14.2%) of the study area; 18% protected) are concentrated mainly in the central and eastern portions of the MHE. There were 824 fires (2 to 228,065 ha) from 1984–2021, with 24% overlapping the wildland–urban interface. Regional temperatures have increased by 1.5 °C, with a 16% reduction in precipitation and stream flow since 1970 that under worst-case emission scenarios may increase temperatures another 3 to 8 °C by the century’s end. The unique biodiversity of the MHE can be better maintained in a rapidly changing climate via at least a three-fold increase in protected areas, co-management of focal species with tribes, and strategic use of fuel treatments nearest communities.