Justin Teisberg, Wayne Kasworm, Michael Proctor, Thomas Radandt, Jennifer
Fortin-Noreus, Hilary Cooley

Huckleberries (Vaccinium spp.) are a food of nutritional importance to grizzly bears (Ursus
arctos) within interior populations of North America, providing sugar-rich calories in the late
summer and fall seasons prior to denning. We developed a resource selection function of high-
quality huckleberry habitat important to Cabinet-Yaak and Selkirk grizzly bears, using field-
verified huckleberry foraging radiolocations acquired during prime months of huckleberry
fruiting (July 15 – September 15, 2010–2019, from 22 female grizzly bears). Stepwise logistic
regression analysis identified 12 significant variables in predicting huckleberry habitat
important to female grizzly bears; all were included in a predictive model (Somers’ D = 0.729; K-
S statistic = 0.570, P < 0.00001). Most influential variables (P < 0.00001; positive [+] or negative
[-] relationship) include canopy closure (-), moisture deficit (-), time since last wildfire (-), solar
radiation (+), snow water equivalent (-), and growing degree days above 5°C (-). On average, 28
percent of an adult female annual home range includes predicted huckleberry habitat (x̄ = 61 ±
6.4 [SE] square kilometers). Seasonal ranges of females overlap extensively within predicted
huckleberry habitat, and degree of overlap trends with quality of habitat. Mothers and
daughters display similar selection patterns for predicted huckleberry habitat, suggesting
huckleberries are an important component to range expansion of these populations. Using
energetic predictions of huckleberry foraging in these areas, we find that a smaller average
body size of Cabinet-Yaak and Selkirk adult females (x̄ = 94 kilograms lean body mass) lessens
the energetic constraints of a huckleberry-dominant diet and may be a direct outcome of
huckleberries being a primary food resource for these populations.

Csaba Domokos, Sebastian Collet, Carsten Nowak, Ferenc Jánoska, Bogdan
Cristescu

Major road developments are planned or ongoing throughout the range of the Romanian
brown bear (Ursus arctos) population, which is numerically the largest in the European Union.
The planned A8 (Tîrgu Mureș–Iași–Ungheni) highway crosses the Romanian Eastern Carpathians
on their entire width, posing a risk to the Romanian and broader transfrontier Carpathian bear
population. In the summers of 2014, 2017 and 2020, we surveyed an 80 km-long section of the
planned highway using baited hair traps (n = 68 throughout all sessions, with three additional
traps active only in 2020) mounted in pairs along the route. We aimed to assess bear
occurrence, movement, and to estimate the minimum number and sex ratio of bears present in
the area. With an effort of 3,519 hair trapping days (17 days / trap / session), we identified 24
individuals from the collected hair samples (n = 45), with a higher prevalence of female bears
(male:female sex ratio of 1:1.3). We did not document individual bears crossing the planned
highway, but detected functional connectivity across the planned highway through parent-
offspring (4 cases), full-sib (2 cases) and half-sib (24 cases) genetic relationships among sampled
individuals. We analyzed habitat characteristics and human-related covariates associated with
hair trap locations to identify influences on bear presence and found that terrain ruggedness
and longitude were the most important predictors of bear occurrence. Bears consistently
occurred in rugged terrain in the Western part of the study area, and were often detected close
(< 1 km) to human settlements. Even before the construction of the A8 highway, connectivity is
likely already limited by the existing extensive network of settlements, being restricted to a few
important linkage areas still free of developments. Additional threats to bears and other wildlife
in the area include poaching and large numbers of free-ranging dogs. We provide
recommendations to mitigate these threats.

Anthony Pagano, Karyn D. Rode, Kerry L. Nicholson, Nicholas J. Lunn, David
McGeachy, William B. Leacock, Charles T. Robbins

Climate warming is increasing polar bear land use across much of their range. While on land
polar bears are without access to their primary seal prey and have been shown to lose body
mass potentially making them vulnerable to starvation. Yet, in some areas, polar bear land use
overlaps with Arctic grizzly bear habitat, where terrestrial foods are sufficient to sustain grizzly
bears. We measured the energy expenditure, changes in body mass, behavior, diet,
movements, and activity of 12 Arctic grizzly bears on the North Slope of Alaska over 17 – 22
days between August to September to compare to similar measures collected from 20 polar
bears on land in Manitoba, Canada. Across 4 age and sex classes, Arctic grizzly bears largely
gained mass over 3 weeks (mean = 0.2 kg/day, range: -0.20 – 0.65 kg/day), while polar bears
lost mass with the exception of one individual (mean = -0.9 kg/day, range: -1.7 – 1.6 kg/day).
On average, Arctic grizzly bears moved 2.8× greater distances. The mean mass-specific energy
expenditure of two Arctic grizzly bears was 2.7× greater than the mean energy expenditure of
20 polar bears on land and similar to the mean energy expenditure of polar bears on the spring
sea ice. Grizzly bears consumed waterfowl, vegetation, berries, fish, moose, and caribou, while
polar bears consumed waterfowl, vegetation, berries, seal, and beluga. Our findings indicate
that the smaller body size of Arctic grizzlies (50% lower body mass than the polar bears we
sampled) allows them to more efficiently forage on terrestrial foods relative to polar bears.
Nevertheless, although terrestrial foods largely compensated for the energy expended to
acquire them, they provided relatively small energetic surpluses during a period when grizzlies
are typically building fat deposits in advance of winter hibernation. These findings reinforce the
hypothesis that most terrestrial foods within the polar bear’s range are inadequate to prolong
the period they can survive on land.

Shelley Marshall, Dexter Hodder, Matt Scheideman, Kara MacAulay, Clayton Lamb,
David Breault, Adrian Batho, Morgan Anderson

Conservation and stewardship of wildlife requires an understanding of how landscape and
climate change influence the interactions between wildlife and their environment. Grizzly bears
(Ursus arctos) in central B.C. rely primarily on plant-based foods and terrestrial meat sources to
meet their energetic requirements though are known to sometimes consume kokanee salmon.
Abnormal weather patterns can vary food availability through late spring green-up, berry crop
failures, or droughts constraining fish movement. Climate and landscape change can accentuate
effects on temperatures, water flow, and precipitation. Given the effects of landscape and
climate change on fish spawning, managers must understand if kokanee are important to these
grizzly bears to consider appropriate actions to maintain this food source. Through five years of
non-invasive hair sampling along three kokanee streams, we quantified the use of kokanee by
grizzly bears. As predicted, spawning kokanee were an important food source in our study area.
We detected 89 individual grizzly bears at these streams which reside in two of the lowest
density population units of grizzly bears in B.C. Isotope and mercury analysis demonstrated the
importance of this kokanee resource given its relatively short availability (~30 days). Mark-
recapture analysis found a positive relationship between berry abundance and bear use of the
kokanee streams. This may be an example of macronutrient optimization as the habitat in and
around these kokanee spawning streams was a mosaic of riparian retention and cutblocks
supporting both berry production and kokanee spawning habitat. We recommend protection
measures to maintain the integrity of the spawning grounds, identification of nearby kokanee
spawning streams and similar protections considered, and continued monitoring to provide
additional insights into the importance of kokanee beyond the variability in conditions
(drought, fires, high water) captured during this study.

Karyn Rode, Todd Atwood, Ryan Wilson, Jeff Bromaghin, Anthony Pagano, Dave
Douglas

Polar bears are recognized in 19 populations across the circumpolar Arctic. Across their range
they occupy habitats that vary in annual sea ice dynamics, ecology, and rates and degrees of
sea ice loss. Over the past decade, a wide range of studies have been conducted that shed light
on polar bear ecology and their limits to adapting to environmental change. The two adjacent
populations with ranges in Alaska have provided informative case studies. Both populations
occupy habitats in which sea ice is available year-round but retreats northward in the summer.
As sea ice loss has occurred, both populations have increasingly summered on land. In the
southern Beaufort Sea (SBS), bears come onshore in northern Alaska where most bears feed on
the remains of subsistence-harvested bowhead whales. In the Chukchi Sea (CS), the majority of
bears that summer on land come to Wrangel and Herald islands as sea ice retreats, the
northernmost land masses. In contrast to SBS bears, CS bears largely rest along the immediate
coastline. However, despite access to a consistent and predictable food resource on shore in
the SBS, the population declined in recent years whereas the CS population has appeared
stable. Studies of bear behavior and ecology on the sea ice suggest that SBS bears had a series
of years with poor access to prey over the narrow continental shelf leading to low cub survival
and subsequent population decline. In contrast, polar bears in the CS occupy habitat over a
vast, shallow continental shelf that appears to support higher densities, abundance, and wider
distribution of bearded and ringed seals. As summer and spring sea ice loss have occurred in
the CS, bears appear to have maintained access to their prey. This presentation will synthesize
multiple studies conducted in the two populations that suggest that differences in regional
ecology and geography play important roles in determining polar bear sensitivity to sea ice loss.

Louise C Archer, Stephen N Atkinson, Nicholas J Lunn, Stephanie R Penk, Péter K
Molnár

The Arctic is the fastest warming region on Earth, threating the persistence of Artic species.
Polar bears are particularly vulnerable because warming leads to declines in their essential sea-
ice foraging habitat. Longer ice-free periods have been linked with declining metrics of
population health, but a data-validated framework quantifying the processes linking sea-ice
dynamics to polar bear vital rates is lacking, limiting our ability to quantify risk and proactively
manage populations. To determine the quantitative links between physiology, population
dynamics, and environmental change, we developed an individual-based bioenergetic model
that incorporates key energetic processes across a polar bear’s lifecycle. We used the model to
reconstruct the dynamics of polar bears in Western Hudson Bay across four decades under
observed sea-ice conditions. We then compared outputs from model hindcasts to long-term
population monitoring data (1979-2016) and found that the model was able to successfully
capture empirical trends in individual morphometrics, reproduction metrics, and overall
population size. The modelling framework demonstrates that an observed decline in a sentinel
population of polar bears can be mechanistically explained by the effects of sea-ice loss on
individual energy budgets, which scale up to influence population vital rates.

Russell Van Horn, Denisse Mateo Chero, Fernando Hancco Pacha, Flynn B
Vickowski, Ronald R Swaisgood, Mathias W Tobler, Megan A Owen

It is not well known what determines the Andean bear’s current habitat use. Thus, we cannot
predict its future habitat use, because Andean forest composition is shifting under climate
change. In addition, although seasonal habitat use has been predicted for Andean bears, there
have been few data to test this prediction. To begin addressing these questions, we installed
camera traps at 102 locations within the Manu Biosphere Reserve of SE Peru, descending from
treeline (~3750masl) to the Amazon rainforest (532masl). From 2016–2022, across 84,266
camera-days (c-d), we recorded 597 independent detections of 25 adult bears. Although 21%
of sampling effort (18,223 c-d) was below 1500 masl, <1% of bear detections (n=4) were
recorded at that elevation. To begin evaluating seasonal shifts in habitat use, we split data into
the dry season (May–Oct; 42,115 c-d) and the wet season (Nov–Apr; 42,151 c-d). We recorded
249 independent detections of bears in the dry season (0.59 detections/100 c-d), at an average
elevation of 2992 masl (839-3586, SD=664.7). We also recorded 348 independent detections of
bears in the wet season (0.83 detections/100 c-d), at an average elevation of 3031 masl (811-
3586, SD=628.5). Neither the rate of detections (p=0.49), nor their elevations (p=0.46), varied
between seasons. Thus, unless future individual-based analyses show the contrary, we see no
seasonal changes in elevation by bears in this landscape. The entire forested gradient above
1500masl appears to be year-round bear habitat, possibly due to the high diversity and
heterogeneity of these forests. In contrast, although lowland Amazonian forests are more
biodiverse, they appear unsuitable for bears, possibly due to the presence of jaguars, or due to
an unknown combination of abiotic factors. Without knowing what factors restrict these bears,
we cannot predict how their distribution will change, or suggest interventions. Future
collaborative large-scale analyses may guide mitigation plans.

Jennifer Fortin-Noreus, Dan Tyers, Andy Pils, Justin E. Teisberg, Joy Erlenbach,
Hilary Cooley

Grizzly bears in the Greater Yellowstone Ecosystem (GYE) are opportunistic omnivores that
move seasonally within their home ranges depending on food abundance. While grizzly bears
supplement their diet with lower-caloric foods that tend to be widely distributed and readily
available (vegetation, insects, fungi, berries, small mammals), the availability and distribution of
high-caloric foods in the GYE (e.g., ungulates, army cutworm moths, whitebark pine seeds) has
the potential to influence seasonal movements of grizzly bears. Previous studies have
investigated grizzly bear use of whitebark pine seeds and ungulates, yet little is known about
grizzly bear use and availability of army cutworm moths. Some grizzly bears whose home
ranges overlap with army cutworm moth aggregation sites appear to forage extensively on
moths during mid-to-late summer when the moths aggregate on remote, high-elevation talus
slopes, but many questions remain regarding the importance of this food source to the GYE
grizzly bear population. The Interagency Grizzly Bear Study Team annually monitors trends in
grizzly bear presence at confirmed moth sites through aerial observations, providing an indirect
measure of the importance of moths in a given year. Using stable isotope analysis (δ15N, δ13C,
δ2H), we present a method to instead directly estimate the proportion of assimilated diet
composed of army cutworm moths. Likely because of their migratory life history, the hydrogen
isotopic ratio (δ2H) of army cutworm moths at confirmed aggregation sites is unique when
compared to other food items in the GYE. Additionally, hair samples were collected and
analyzed from 1) bears at or near confirmed moth sites and 2) collared bears with no GPS
locations at confirmed moth sites. Moths, other dietary items, and hair samples will be
collected from additional peaks during 2020 for expanded analysis.

Ramona Maraj, Nolan Waters, Emily Gavey, Peter Demontigny, Erin Henderson,
Rachel Stapleton

Expansion of and increase in human modification between 1990 and 2015 resulted in
1.6 million km2 of natural land lost globally. We examined the implications of this on grizzly
bear denning habitat in seven Canadian national parks. We used 417 den locations across seven
western Canadian national parks, ranging through British Columbia, Alberta, the Northwest
Territories and Yukon. Den locations were obtained from aerial sightings, staff or public
sightings, and collared bears. We used MaxEnt to model the influence of 21 covariates on third
order den site selection across the extent of the study area. To model the fundamental niche
for den selection, we considered a model without any anthropogenic influence. We
subsequently considered a realized niche den model that incorporated distance to linear
features and global human modification as explanatory variables. Our fundamental niche model
showed that across grizzly bear range, the visibility of the sky and solar radiation were
important factors that drive den selection. Our models also showed that denning habitat
availability decreases with latitude, until the Arctic coast, where availability becomes
widespread again. Our realized niche model showed that anthropogenic influences were the
most important factor influencing den site selection, with global human modification
contributing almost 50% explanatory power to the model and creating a disproportional loss of
denning habitat across all parks. At current rates of human modifications, availability of denning
habitat may become limiting for bears, even in protected areas.

Tracy McKay and Laura Finnegan

Forest harvesting is a primary agent of change across the boreal forest of Canada, altering black
bear and grizzly bear habitat. Silviculture practices applied after forest harvesting directly
impact forage availability for bears, but there is limited research on how specific silviculture
treatments (preparation, planting, tending) influence bear use of harvest blocks and co-
occurrence with other species. We used camera detections, silviculture data, landscape
characteristics, and vegetation data from 117 harvest blocks sampled in Alberta, Canada during
2018-2020 to assess the influence of silviculture practices, block characteristics, surrounding
habitat, and forage abundance on black bear and grizzly bear occurrence and co-occurrence
with prey species. We found black bear occurrence was higher in blocks that had been planted,
and grizzly bear occurrence was higher in blocks that had been stand tended and with higher
tree-planting densities. Black bear occurrence was higher in smaller blocks, and grizzly bear
occurrence was higher in blocks where the surrounding area had lower densities of linear
disturbances and harvest blocks. Black bear occurrence was higher in blocks with greater
availability of fireweed, and both black and grizzly bear occurrence was higher in blocks with
greater availability of rose. Co-occurrence analysis indicated that black bear occurrence was
higher in blocks where white-tailed deer were detected, and grizzly bear occurrence was higher
where mule deer were detected. Our study indicates that bear use of harvest blocks is driven by
fine-scale block characteristics and silviculture practices as well as the habitat surrounding the
block, and harvest blocks may directly influence predator-prey dynamics. The results of our
study may be used to inform sustainable forest management that considers the impacts of
forest harvesting practices on black bears, grizzly bears, and their prey species.

Anne G. Hertel, Aida Parres, Shane C. Frank, Julien Renaud, Nuria Selva, Andreas
Zedrosser, Niko Balkenhol, Luigi Maiorano, Ancuta Fedorca, Trishna Dutta, Neda
Bogdanović, Silviu Chiriac, Duško Ćirović, Paolo Ciucci, Csaba Domokos, Mihai Fedorca, Stefano
Filacorda, Claudio Groff, Miguel de Gabriel Hernando, Djuro Huber, Georgeta Ionescu, Klemen
Jerina, Alexandros A. Karamanlidis, Jonas Kindberg, Ilpo Kojola, Yorgos Mertzanis, Santiago
Palazon, Mihai I. Pop, Maria Psaralexi, Pierre Yves Quenette, Agnieszka Sergiel, Michaela
Skuban, Diana Zlatanova, Tomasz Zwijacz-Kozica, Marta De Barba

Species often occupy wide-geographical ranges with contrasting environmental conditions that
shape intraspecific variation in space use. Three-quarters of the planet's land surface have been
altered by humans with consequences for animal movement and related ecosystem
functioning. Yet, limited data availability across species' ranges has constrained our
understanding of intraspecific movement variation in highly anthropized landscapes. Leveraging
a unique dataset of 751 brown bear (Ursus arctos) GPS-movement trajectories that included
almost the entire geographical range of this species in Europe, we investigated intraspecific
variation in space use along a gradient of human impact and resource availability. We
quantified individual space use at different temporal scales, from home range sizes to 10-day
and 1-day displacement distances. We found large intraspecific variation in space use across all
temporal scales, with males roaming farther than females. This variation was profoundly
affected by human activity (i.e., human footprint index) and resource availability (i.e., annual
vegetation productivity and forest disturbances). Bears occupied smaller home ranges and
moved less in more anthropized landscapes and in areas of higher resource availability. Bear
home ranges overlapped little with protected areas, e.g., only 8 bears had their entire home
ranges within protected areas, demonstrating that protected areas in Europe are too small to
sustain brown bear populations. On a population level, bears from the Carpathian, Dinaric
Pindos, and Eastern Balkan moved most, followed by bears from Fennoscandia, while bears
from the Alpine and Apennine moved most. Restricted bear movements in areas of high human
footprint hinders connectivity among some populations in south-central Europe which are close
in proximity. In areas of high human footprint, such as the Italian Alps or Serbia, establishing
and maintaining movement corridors is essential to promote connectivity.