Grizzly Research Articles

Intraspecific encounters can lead to reduced range overlap

Direct encounters, in which two or more individuals are physically close to one another, are a topic of increasing interest as more and better movement data become available. Recent progress, including the development of statistical tools for estimating robust measures of changes in animals’ space use over time, facilitates opportunities to link direct encounters between individuals with the long-term consequences of those encounters. Working with movement data for coyotes (Canis latrans) and grizzly bears (Ursus arctos horribilis), we investigate whether close intraspecific encounters were associated with spatial shifts in the animals’ range distributions, as might be expected if one or both of the individuals involved in an encounter were seeking to reduce or avoid conflict over space. We analyze the movement data of a pair of coyotes in detail, identifying how a change in home range overlap resulting from altered movement behavior was apparently a consequence of a close intraspecific encounter. With grizzly bear movement data, we approach the problem as population-level hypothesis tests of the spatial consequences of encounters. We find support for the hypotheses that (1) close intraspecific encounters between bears are, under certain circumstances, associated with subsequent changes in overlap between range distributions and (2) encounters defined at finer spatial scales are followed by greater changes in space use. Our results suggest that animals can undertake long-term, large-scale spatial changes in response to close intraspecific encounters that have the potential for conflict. Overall, we find that analyses of movement data in a pairwise context can (1) identify distances at which individuals’ proximity to one another may alter behavior and (2) facilitate testing of population-level hypotheses concerning the potential for direct encounters to alter individuals’ space use.

The influence of social identity on attitudes toward wildlife.

Wildlife conservation depends on supportive social as well as biophysical conditions. Social identities such as hunter and nonhunter are often associated with different attitudes toward wildlife. However, it is unknown whether dynamics within and among these identity groups explain how attitudes form and why they differ. To investigate how social identities help shape wildlife-related attitudes and the implications for wildlife policy and conservation, we built a structural equation model with survey data from Montana (USA) residents (n=1758) that tested how social identities affect the relationship between experiences with grizzly bears (Ursus arctos horribilis) and attitudes toward the species. Model results (r2=0.51) demonstrated that the hunter identity magnified the negative effect of vicarious property damage on attitudes toward grizzly bears (β=-0.381, 95% confidence interval [CI]: -0.584 to -0.178, p<0.001), which in turn strongly influenced acceptance (β=-0.571, 95% CI: -0.611 to -0.531, p<0.001). Our findings suggested that hunters' attitudes toward grizzly bears likely become more negative primarily because of in-group social interactions about negative experiences, and similar group dynamics may lead nonhunters to disregard the negative experiences that out-group members have with grizzly bears. Given the profound influence of social identity on human cognitions and behaviors in myriad contexts, the patterns we observed are likely important in a variety of wildlife conservation situations. To foster positive conservation outcomes and minimize polarization, management strategies should account for these identity-driven perceptions while prioritizing conflict prevention and promoting positive wildlife narratives within and among identity groups. This study illustrates the utility of social identity theory for explaining and influencing human-wildlife interactions.

Understanding the Hidden Costs and Benefits of Living With Grizzly Bears in Montana

Wildlife sometimes impose unmitigated costs and provide unevenly distributed benefits that exacerbate conflict among people or between wildlife and groups of people. Although previous research has primarily focused on the visible effects of wildlife, reducing conflict will require a broader understanding of wildlife effects on human well-being. Using a “noticing, collecting, thinking” analysis of 25 interviews with people living near grizzly bears in Montana, USA, we provide a nuanced profile of their perceived costs and benefits, including hidden and nonmaterial effects. Interviewees described the interconnected nature of grizzly bear effects on people, where visible effects on livelihoods, health, social relations, personal security, and freedom led to negative hidden effects such as threats to cultural identity and diminished perceptions of livelihood sustainability. Positive effects included enhanced mental, spiritual, and cultural well-being, such as enhanced feelings of connection to wild places. We discuss how this broader understanding of wildlife costs and benefits helps provide a more thorough understanding of the effects of living with grizzly bears.

The wildlife attitude-acceptability framework’s potential to inform human dimensions of wildlife science and practice

ABSTRACT Despite years of research, concepts such as human tolerance and acceptability of wildlife remain inconsistently defined and measured, creating confusion, undermining comparative and longitudinal research, and limiting utility to practitioners. To address these shortcomings, the wildlife attitude-acceptability framework proposed intersecting attitudes toward wildlife species with acceptability of impacts from that species to reveal four archetypes of human cognitions toward wildlife. Here, we use data from western US household surveys to populate the conceptual space of the wildlife attitude-acceptability framework with human cognitions toward three carnivore species: gray wolf (Canis lupis), cougar (Puma concolor), and grizzly bear (Ursus arctos horribilis). This empirical application of the wildlife attitude-acceptability framework demonstrates its potential to inform management and conservation efforts, promote consistent measurement across species and studies, and extend theoretical understanding of concepts like tolerance, which are necessary for human–wildlife coexistence. We discuss these opportunities and remaining needs for improvement before wider adoption.

Human disturbance in riparian areas disrupts predator-prey interactions between grizzly bears and salmon.

Wildlife must increasingly balance trade-offs between the need to access important foods and the mortality risks associated with human-dominated landscapes. Human disturbance can profoundly influence wildlife behavior, but managers know little about the relationship between disturbance-behavior dynamics and associated consequences for foraging. We address this gap by empirically investigating the consequences of human activity on a keystone predator-prey interaction in a region with limited but varied industrial disturbance. Using stable isotope data from 226 hair samples of grizzly bears (Ursus arctos horribilis) collected from 1995 to 2014 across 22 salmon-bearing watersheds (88,000 km2) in British Columbia, Canada, we examined how human activity influenced their consumption of spawning salmon (Oncorhynchus spp.), a fitness-related food. Accounting for the abundance of salmon and other foods, salmon consumption strongly decreased (up to 59% for females) with increasing human disturbance (as measured by the human footprint index) in riparian zones of salmon-bearing rivers. Declines in salmon consumption occurred with disturbance even in watersheds with low footprints. In a region currently among the least influenced by industrial activity, intensification of disturbance in river valleys is predicted to increasingly decouple bears from salmon, possibly driving associated reductions in population productivity and provisioning of salmon nutrients to terrestrial ecosystems. Accordingly, we draw on our results to make landscape-scale and access-related management recommendations beyond current streamside protection buffers. This work illustrates the interaction between habitat modification and food security for wildlife, highlighting the potential for unacknowledged interactions and cumulative effects in increasingly modified landscapes.

Lack of reinforcement is hard to “bear”: Assessing judgment bias in grizzly bears (Ursus arctos horribilis)

ABSTRACT Cognitive biases reveal underlying affective state by indicating optimism and pessimism. This methodology may permit assessment of positive welfare in animals that have few validated positive welfare indicators, such as bears. Our goal was to validate a judgment bias test for assessing optimism in brown bears, using a touchscreen. After training the bears on a conditional discrimination, we compared responses to an ambiguous stimulus in a 2 × 2 nested design involving four experimental conditions representing presence or absence of a behind-the-scenes tour and presence or absence of a keeper training session with food reinforcement. We recorded bears’ behavior during the conditions as a measure of convergent validity. Testing revealed the possibility of pessimism in the absence of reinforcement in one bear. More frustration behaviors were also observed during the no food reinforcement conditions. This is the first experimental demonstration of brown bears using a touchscreen and one of only three reports in which bears have been reported to perform a conditional discrimination. This method of assessing underlying affective state shows promise for the future.

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.

Faulkner’s Renewal of the Figure of the Grizzly Bear in the American West: From Ancestor to Political Symbol

The role of the grizzly bear in many Native American tribes has had a tremendous cultural, spiritual and ecological significance, which was objected by the colonisers’ anthropocentric conception of wildlife as an instrumental value to humans. Literature has been one of the main sources to find traces of this Native American conception of the grizzly bear as deity as well as the colonists’ perspective of the nonhuman animal as threat to be tamed. In this article, I will analyse some folk tales and William Faulkner’s “The Bear” (1942) in order to demonstrate the existence of this conception of the grizzly bear in the American West, as well as the importance of literature for its perpetuation.

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.

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 (Juniperus 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.

Observations of Grizzly Bear (&lt;i&gt;Ursus arctos&lt;/i&gt;) associated with abundance of spawning Kokanee (&lt;i&gt;Oncorhynchus nerka&lt;/i&gt;) at an inland river, British Columbia, Canada

Salmon (Oncorhynchus spp.) are an important food source for Grizzly Bear (Ursus arctos), but many salmon populations are declining. While most research on Grizzly Bear–salmon interactions occurs in coastal ecosystems, declining salmon may also affect Grizzly Bears in inland ecosystems where salmon are also an important part of their diet. We document changes in the number and distribution of observations of Grizzly Bears and changing Kokanee (i.e., landlocked Sockeye Salmon, Oncorhynchus nerka) abundance at an inland river. We hypothesized that reduced abundance of Kokanee would limit the number of Grizzly Bear observations at the river. We compared Kokanee abundance and Grizzly Bear observations (n = 535) between 2012 and 2019 at the Lardeau River, British Columbia, Canada. We used a generalized linear mixed model to test if the number of bear observations changed as a function of Kokanee abundance among four river reaches during eight consecutive years of study. Kokanee abundance was a strong statistical predictor of Grizzly Bear observations (β = 0.52, P = 0.001, CI = 0.12–0.87), and Kokanee abundance and reach explained 73% of the variance. Our results suggest that reduced Kokanee abundance also reduces Grizzly Bear presence, likely because bears seek out other, more available food sources, away from Kokanee spawning habitat. This pattern could limit ecosystem services provided by Grizzly Bears adjacent to spawning areas and it could have implications for bear management and conservation.

Evolution ofanelloviruses from a circovirus-like ancestor through gradual augmentation ofthe jelly-roll capsid protein.

Anelloviruses are highly prevalent in diverse mammals, including humans, but so far have not been linked to any disease and are considered to be part of the 'healthy virome'. These viruses have small circular single-stranded DNA (ssDNA) genomes and encode several proteins with no detectable sequence similarity to proteins of other known viruses. Thus, anelloviruses are the only family of eukaryotic ssDNA viruses currently not included in the realm Monodnaviria. To gain insights into the provenance of these enigmatic viruses, we sequenced more than 250 complete genomes of anelloviruses from nasal and vaginal swab samples of Weddell seal (Leptonychotes weddellii) from Antarctica and a fecal sample of grizzly bear (Ursus arctos horribilis) from the USA and performed a comprehensive family-wide analysis of the signature anellovirus protein ORF1. Using state-of-the-art remote sequence similarity detection approaches and structural modeling with AlphaFold2, we show that ORF1 orthologs from all Anelloviridae genera adopt a jelly-roll fold typical of viral capsid proteins (CPs), establishing an evolutionary link to other eukaryotic ssDNA viruses, specifically, circoviruses. However, unlike CPs of other ssDNA viruses, ORF1 encoded by anelloviruses from different genera display remarkable variation in size, due to insertions into the jelly-roll domain. In particular, the insertion between β-strands H and I forms a projection domain predicted to face away from the capsid surface and function at the interface of virus-host interactions. Consistent with this prediction and supported by recent experimental evidence, the outermost region of the projection domain is a mutational hotspot, where rapid evolution was likely precipitated by the host immune system. Collectively, our findings further expand the known diversity of anelloviruses and explain how anellovirus ORF1 proteins likely diverged from canonical jelly-roll CPs through gradual augmentation of the projection domain. We suggest assigning Anelloviridae to a new phylum, 'Commensaviricota', and including it into the kingdom Shotokuvirae (realm Monodnaviria), alongside Cressdnaviricota and Cossaviricota.

Transcriptome Profiling Reveals Enhanced Mitochondrial Activity as a Cold Adaptive Strategy to Hypothermia in Zebrafish Muscle.

The utilisation of synthetic torpor for interplanetary travel once seemed farfetched. However, mounting evidence points to torpor-induced protective benefits from the main hazards of space travel, namely, exposure to radiation and microgravity. To determine the radio-protective effects of an induced torpor-like state we exploited the ectothermic nature of the Danio rerio (zebrafish) in reducing their body temperatures to replicate the hypothermic states seen during natural torpor. We also administered melatonin as a sedative to reduce physical activity. Zebrafish were then exposed to low-dose radiation (0.3 Gy) to simulate radiation exposure on long-term space missions. Transcriptomic analysis found that radiation exposure led to an upregulation of inflammatory and immune signatures and a differentiation and regeneration phenotype driven by STAT3 and MYOD1 transcription factors. In addition, DNA repair processes were downregulated in the muscle two days' post-irradiation. The effects of hypothermia led to an increase in mitochondrial translation including genes involved in oxidative phosphorylation and a downregulation of extracellular matrix and developmental genes. Upon radiation exposure, increases in endoplasmic reticulum stress genes were observed in a torpor+radiation group with downregulation of immune-related and ECM genes. Exposing hypothermic zebrafish to radiation also resulted in a downregulation of ECM and developmental genes however, immune/inflammatory related pathways were downregulated in contrast to that observed in the radiation only group. A cross-species comparison was performed with the muscle of hibernating Ursus arctos horribilis (brown bear) to define shared mechanisms of cold tolerance. Shared responses show an upregulation of protein translation and metabolism of amino acids, as well as a hypoxia response with the shared downregulation of glycolysis, ECM, and developmental genes.

Examining Visitor Collected Species Data from Denali National Park and Preserve

In citizen science programs, the concept of “participant” is often used as a catch-all without considering how different participants (e.g., young, old, wealthy, poor, differently-abled, local inhabitants, and visitors) affect scientific outcomes of citizen science programs (e.g., the data collection, data analysis, publications, etc.). This research advances the understanding of tourist participants’ ability to produce data comparable to participants who live near the study area. To examine data collected by tourist participants, we performed a case study on wildlife observation data collected through the Map of Life-Denali program in Denali National Park and Preserve in Alaska, USA. The species observation data collected by tourists and Alaska Residents were compared visually using heatmaps and statistically with the Ripley’s K function variation, the L function. Results from the analysis show that the tourist and resident data have similar point patterns for the three species we compared, <em>Ursus arctos</em> (Grizzly Bear), <em>Rangifer tarandus</em> (Caribou), and <em>Alces alces</em> (Moose). Our results indicate that tourists can be effective citizen science participants. And show the potential for leveraging this large pool of untapped participants in popular tourist destinations such as U.S. National Parks.

Using Stable Isotopes to Determine Natal Origin and Feeding Habits of the Army Cutworm Moth, Euxoa auxiliaris (Lepidoptera: Noctuidae).

The army cutworm, Euxoa auxiliaris (Grote), is a migratory noctuid that is both an agricultural pest and an important late-season food source for grizzly bears, Ursus arctos horribilis (Linnaeus, Carnivora: Ursidae), within the Greater Yellowstone Ecosystem. Beyond the confirmation of the moths' seasonal, elevational migration in the mid-1900s, little else has been documented about their migratory patterns. To address this missing ecological component, we examined (1) migratory routes during their spring and fall migratory periods throughout their natal range, the Great Plains, and (2) natal origin at two of their summering ranges using stable hydrogen (δ2H) analyses of wings from samples collected within the areas of interest. Stable carbon (δ13C) and stable nitrogen (δ15N) analyses of wings were used to evaluate larval feeding habits of the migrants and agricultural intensity of natal origin sites, respectively. Results suggest that, rather than migrating exclusively east to west, army cutworm moths are also migrating north to south during their spring migration. Moths did not exhibit natal origin site fidelity when returning to the Great Plains. Migrants collected from the Absaroka Range had the highest probability of natal origin in Alberta, British Columbia, Saskatchewan, the most southern region of the Northwest Territories, and second highest probability of origin in Montana, Wyoming, and Idaho. Migrants collected in the Lewis Range had the highest probability of origin in the same provinces of Canada. Results suggest that migrants of the Absaroka Range fed exclusively on C3 plants as larvae and rarely fed in heavily fertilized agroecosystems.

Investigating the effects of chronic low-dose radiation exposure in the liver of a hypothermic zebrafish model

Mankind’s quest for a manned mission to Mars is placing increased emphasis on the development of innovative radio-protective countermeasures for long-term space travel. Hibernation confers radio-protective effects in hibernating animals, and this has led to the investigation of synthetic torpor to mitigate the deleterious effects of chronic low-dose-rate radiation exposure. Here we describe an induced torpor model we developed using the zebrafish. We explored the effects of radiation exposure on this model with a focus on the liver. Transcriptomic and behavioural analyses were performed. Radiation exposure resulted in transcriptomic perturbations in lipid metabolism and absorption, wound healing, immune response, and fibrogenic pathways. Induced torpor reduced metabolism and increased pro-survival, anti-apoptotic, and DNA repair pathways. Coupled with radiation exposure, induced torpor led to a stress response but also revealed maintenance of DNA repair mechanisms, pro-survival and anti-apoptotic signals. To further characterise our model of induced torpor, the zebrafish model was compared with hepatic transcriptomic data from hibernating grizzly bears (Ursus arctos horribilis) and active controls revealing conserved responses in gene expression associated with anti-apoptotic processes, DNA damage repair, cell survival, proliferation, and antioxidant response. Similarly, the radiation group was compared with space-flown mice revealing shared changes in lipid metabolism.

“And do a Grizzly”: Djuna Barnes and Dancing Animals in the New York Press

ABSTRACT The “Grizzly Bear” animal dance sparked the social dance craze that swept the United States in the 1910s, causing a moral panic about the unseemly movements and erotic energies of this new popular leisure form. Djuna Barnes’s New York journalism on dance serves to connect these animal dances to the “eruption of animality in artistic and cultural texts” that Carrie Rohman has traced in modernism. Exploring social dance, Irene Castle’s career, and Barnes’s journalism, this article examines assemblages of bears and other dancing (human and nonhuman) animals to foreground the intersection of modernist animal ontologies with elusive histories of social dance.

GRIZZLY BEAR DENNING HABITAT AND DEMOGRAPHIC CONNECTIVITY IN NORTHERN IDAHO AND WESTERN MONTANA

Grizzly Bears (Ursus arctos) are protected in the contiguous United States under the federal Endangered Species Act. The conservation strategy for the species encourages population connectivity between isolated Grizzly Bear Recovery Areas through Demographic Connectivity Areas. Another goal is reestablishment of a breeding population in the Bitterroot ecosystem through natural immigration. Using the locations of 362 verified Grizzly Bear den sites and Maxent as a resource selection function, we predicted 21,091 km2 of suitable denning habitats. Terrain features, distance to roads, and land cover best explained suitable denning habitats in northern Idaho and western Montana. The results support the demographic model for population connectivity, and independent of other factors there is suitable denning habitat for hundreds of Grizzly Bears in the Bitterroot analysis area. We suggest additions to the Bitterroot Grizzly Bear Recovery Area, and that more effective motorized-access management be applied to demographic connectivity areas.

Supplementing Environmental Assessments with Cumulative Effects Scenario Modeling for Grizzly Bear Connectivity in the Bow Valley, Alberta, Canada

Persistence of sensitive wildlife in populated regions requires conservation strategies that address gradual expansion of development footprint and human activity. The project-based environmental assessment regime for municipal development is poorly suited to provide necessary strategic perspective, given its focus on local and short-term impacts. We used the ALCES cumulative effects model to strategically assess impacts to grizzly bears (Ursus arctos) in the Bow Valley of Alberta, Canada. Landscape simulation mapped expansion of past and potential future development footprint in the region over multiple decades. Consequences to movement connectivity for grizzly bears were estimated by applying a least cost path analysis to the landscape simulation. An index of recreational activity was derived from fitness tracking data and integrated with the landscape simulation to model change in recreational activity through time. Maps of grizzly bear connectivity and recreational activity were combined to calculate human-bear conflict risk. The analysis suggests that connectivity has been altered through displacement to upslope areas by settlement expansion, such that surrounding natural areas have become important for grizzly bear connectivity. These areas are also popular for outdoor recreation, resulting in elevated human-bear conflict risk which can be expected to increase if development and human activity continue to expand in high connectivity areas. Conservation of wildlife in populated regions will be supported by broadening the scope of environmental assessment to address cumulative effects of development footprint and human activity over large spatial and temporal scales.

Examining the Effects of Hibernation on Germline Mutation Rates in Grizzly Bears.

A male mutation bias is observed across vertebrates, and, where data are available, this bias is accompanied by increased per-generation mutation rates with parental age. While continuing mitotic cell division in the male germline post puberty has been proposed as the major cellular mechanism underlying both patterns, little direct evidence for this role has been found. Understanding the evolution of the per-generation mutation rate among species requires that we identify the molecular mechanisms that change between species. Here, we study the per-generation mutation rate in an extended pedigree of the brown (grizzly) bear, Ursus arctos horribilis. Brown bears hibernate for one-third of the year, a period during which spermatogenesis slows or stops altogether. The reduction of spermatogenesis is predicted to lessen the male mutation bias and to lower the per-generation mutation rate in this species. However, using whole-genome sequencing, we find that both male bias and per-generation mutation rates are highly similar to that expected for a non-hibernating species. We also carry out a phylogenetic comparison of substitution rates along the lineage leading to brown bear and panda (a non-hibernating species) and find no slowing of the substitution rate in the hibernator. Our results contribute to accumulating evidence that suggests that male germline cell division is not the major determinant of mutation rates and mutation biases. The results also provide a quantitative basis for improved estimates of the timing of carnivore evolution.