Ursus 2024 Volume 35 Articles 16-17

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Grizzly bear and American black bear interactions with people in Yellowstone National Park

Kerry A. Gunther, Kelly M. Atkins, Travis C. Wyman, Eric G. Reinertson

Ursus 2024 (35e16), 1-13, (11 September 2024) https://doi.org/10.2192/URSUS-D-24-00001

KEYWORDS: American black bear, bear attacks, bear–human encounters, bear–human interactions, camping, grizzly bear, hiking, off-trail travel, outdoor recreation, Ursus americanus, Ursus arctos, Yellowstone National Park

Open Access Article

In North America, polar bears (Ursus maritimus), grizzly bears (U. arctos), and American black bears (U. americanus) occasionally injure or kill humans. Although bear-inflicted human injuries are uncommon, they generate media attention that can lead to fear and unreasonable perceptions of the risk of bear attacks. Information on the behavioral responses of grizzly and black bears during interactions with people can provide a factual basis regarding the risks associated with recreating in bear habitats and assist land managers in developing and prioritizing bear safety messages. To address those objectives, we collected 17,171 reports of grizzly and black bear reaction behavior during interactions with people in Yellowstone National Park, USA, between 1991 and 2022. We used Bayesian Multinomial Logistic Regression models to examine the odds of attack, agitation and/or warning, flight, or curious behavioral reactions versus neutral responses in bear–human interactions. We found that reaction behavior depended on both the species involved and the location of the interaction. In developed areas and along roadsides, neutral responses were most likely for both species. On front-country trails, odds of curious or flee reactions were greater than neutral responses for both species. The odds of agitation and/or warning reactions from grizzlies were also greater in this setting. In backcountry campsites, there were marginally higher odds of black bears attacking; whereas, grizzlies had marginally higher odds of attacking during off-trail backcountry interactions. Although bear attacks were uncommon in all locations, grizzlies were ∼3.9× more likely than black bears to injure people in backcountry areas. Bear interactions with people were generally predictable; grizzly and black bears exhibited neutral behaviors or fled during most interactions. Curious approaches, agitation and/or warning behaviors, physical contact, and attacks were uncommon. Safety messages encouraging calm, confident responses during bear–human interactions are warranted, and may have better efficacy than those that generate fear and apprehension.


Sea ice dynamics influence movement patterns of adult female polar bears in southern Hudson Bay

Kevin R. Middel, Martyn E. Obbard

Ursus 2024 (35e17), 1-27, (24 September 2024) https://doi.org/10.2192/URSUS-D-23-00019R1

KEYWORDS: home range, movement patterns, polar bear, sea ice, seasonal movements, Southern Hudson Bay, space use, Ursus maritimus

Open Access Article

To access seals (Pinnipedia), polar bears (Ursus maritimus) move large distances over the sea ice in winter. Already documented declines in ice duration for Hudson Bay, Canada, are predicted to continue, likely affecting polar bear movement patterns. Using data from global positioning system (GPS) collars, 2007–2011, we describe movement patterns of adult female polar bears of the Southern Hudson Bay (SH) subpopulation. We tested effects of season and reproductive class on movement rates, distance travelled, displacement distance and direction, and home range size. Except for denning females, reproductive class had no effect on movement rates, which were greatest during freeze-up and least during summer. Across all reproductive classes and seasons, mean hourly movement rate was 0.63 km/hour. Mean annual distance moved by nondenning females was 4,771 km. During freeze-up, bears moved north-easterly from the Ontario coast toward the Belcher Islands and Québec following the forming ice edge. During breakup, bears moved southerly toward the Ontario coast and away from the residual ice that occurs north of the Ontario coast. In autumn, denning females moved southerly and inland to den. Mean annual minimum convex polygon (MCP) home-range size was 153,866 km2, with no effect of reproductive class nor change over time. Home range estimates from kernel density estimators and Brownian bridge movement models (BBMM) varied by reproductive class and were smaller than MCP ones. The BBMM estimates likely yield more realistic patterns of space use by polar bears. Using data from satellite collars, 1997–2003, we compared travel distance and home range size between periods (1997–2003; 2007–2011). We found weak evidence of a difference in distance moved between periods, perhaps due to a period of ice stability in the 2000s. Our results identified patterns of use of extensive areas of Hudson Bay by SH bears in winter, and results provide benchmarks for future studies of movement patterns.