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Anthropogenic disturbances, including roads, are known to influence animal habitat selection and mortality. In this study, we consider the role of sensory perception in understanding why and how animals respond to disturbances. Our goal was to investigate the effect of visual perception (visibility) around roads on grizzly bear (Ursus arctos horribilis Ord, 1815) habitat selection and mortality in Alberta, Canada. We used detailed topographic and vegetation data from airborne light detection and ranging (lidar) to estimate visibility around roads. We modelled habitat selection as a function of road visibility and environmental variables using GPS telemetry data from 39 grizzly bears and integrated step selection analysis (iSSA). Finally, we assessed mortality risk in visible areas by comparing habitat selection between grizzly bears that died and those that survived. We found that grizzly bears were less likely to select visible areas when moving slowly or resting, but were more likely to select visible areas when travelling. We found that grizzly bears that survived selected for areas farther from roads than grizzly bears that died. However, no difference in selection for visible areas was observed. An exploratory analysis showed that grizzly bear mortalities commonly occurred in visible areas. Our findings highlight the importance of sensory perception in understanding animal behaviour. Key words: anthropogenic disturbance, grizzly bears, habitat selection, integrated step selection analysis, perception, road ecology, Ursus arctos horribilis, visibility. Il est bien etabli que les perturbations d'origine humaine, y compris les routes, influencent la selection d'habitats par les animaux et la mortalite de ces derniers. Nous examinons le role de la perception sensorielle pour comprendre pourquoi et comment les animaux reagissent a des perturbations. L'objectif est d'etudier l'effet de la perception visuelle (la visibilite) autour des routes sur la selection d'habitats et la mortalite de grizzlis (Ursus arctos horribilis Ord, 1815) en Alberta (Canada). Nous utilisons des donnees topographiques et de vegetation detaillees de detection et telemetrie par ondes lumi-neuses (lidar) aeroportees pour estimer la visibilite autour de routes. Nous modelisons la selection d'habitats comme etant une fonction de la visibilite autour des routes et de variables environnementales en utilisant des donnees de telemetrie GPS pour 39 grizzlis et l'analyse de selection de pas integree (iSSA). Enfin, nous evaluons le risque de mortalite dans les secteurs visibles en comparant la selection d'habitats des grizzlis qui meurent et a celle des grizzlis qui survivent. Nous constatons que les grizzlis sont moins susceptibles de choisir des secteurs visibles quand ils se deplacent lentement ou sont au repos, mais plus susceptibles de choisir des secteurs visibles quand ils se deplacent entre differents lieux. Nous constatons que les grizzlis qui survivent choisissent des secteurs plus eloignes de routes que les grizzlis qui meurent. Aucune difference n'est toutefois observee en ce qui concerne la selection de secteurs visibles. Une analyse exploratoire montre que les morts de grizzlis se produisent souvent dans des secteurs visibles. Nos constatations soulignent l'importance de tenir compte de la perception sensorielle pour comprendre les comportements d'animaux. [Traduit par la Redaction] Mots-cles : perturbation d'origine humaine, grizzlis, selection d'habitats, analyse de selection de pas integree, perception, ecologie des routes, Ursus arctos horribilis, visibilite., Introduction The study of animal behaviour is incomplete without considering the overarching effects of human activity. Few wildlife populations are untouched by human activity. In particular, roads are considered the [...]

A study was conducted to determine the accuracy of the method used to determine the number of female grizzly bears with cubs in Yellowstone area. Results showed that the method presented conservative figures but minor changes in the method might give improved results.

I investigated the exploitation of pocket gophers (Thomomys talpoides) by grizzly bears (Ursus arctos horribilis) in the Yellowstone region of the United States with the use of data collected during a study of radiomarked bears in 1977 1992. My analysis focused on the importance of pocket gophers as a source of energy and nutrients, effects of weather and site features, and importance of pocket gophers to grizzly bears in the western contiguous United States prior to historical extirpations. Pocket gophers and their food caches were infrequent in grizzly bear feces, although foraging for pocket gophers accounted for about 20-25% of all grizzly bear feeding activity during April and May. Compared with roots individually excavated by bears, pocket gopher food caches were less digestible but more easily dug out. Exploitation of gopher food caches by grizzly bears was highly sensitive to site and weather conditions and peaked during and shortly after snowmelt. This peak coincided with maximum success by bears in finding pocket gopher food caches. Exploitation was most frequent and extensive on gently sloping nonforested sites with abundant spring beauty (Claytonia lanceolata) and yampah (Perdieridia gairdneri). Pocket gophers are rare in forests, and spring beauty and yampah roots are known to be important foods of both grizzly bears and burrowing rodents. Although grizzly bears commonly exploit pocket gophers only in the Yellowstone region, this behavior was probably widespread in mountainous areas of the western contiguous United States prior to extirpations of grizzly bears within the last 150 years. Key words: excavation, grizzly bears, pocket gophers, Thomomys talpoides, Ursus arctos, Yellowstone

Grizzly bears are important predators of ungulate calves but observations of predation rates are imprecise because of the difficulty in collecting accurate measurements. An investigation of the grizzly bears' predation rates on calves of the internationally important Porcupine Caribou Herd is presented. Continuous aerial observations show predation rates estimated at 2,000-3,000 calves annually, accounting for around 5-7% of the estimated 43,000 calves produced per year.

Ungulates are an important part of the grizzly bears' diet in Yellowstone National Park, particularly during the nondenning period. Much of the ungulate consumption in the spring is through scavenging. A study designed to test bear consumption of carrion and the influence of human activity on their feeding habits shows that grizzly bear behaviour is clearly affected by humans and carcasses near human facilities are underutilized.

Grizzly bears are an endangered species in the US and there is continuing interest in how the species uses available habitat. A study of grizzly bears in the Swan Mountains of Montana examines their use of seven satellite-derived cover types over an eight year period. Results show that avalanche chutes are preferred bear habitats during all seasons, together with slab rock. The least selected habitats are forested areas.

Roots of the biscuitroot (Lomatium cous) are a common food of grizzly bears (Ursus arctos horribilis) in drier parts of their southern range. I used random sampling and locations of radiomarked bears in the Yellowstone ecosystem to investigate the importance of mass and starch content of roots, digability of the site, and density of plants relative to selection of sites by grizzly bears to dig biscuitroots. Where biscuitroots were present, most differences between dug and undug sites were related to digability of the site and mass and starch content of roots. Grizzly bears more often dug in sites where average milligrams of starch per kilogram of pull per root ([approximately equal to]energy gain) was high. Density of biscuitroots was not related to selection of sites by grizzly bears. Mass of biscuitroot stems also provided relatively little information about mass of roots. Distribution of biscuitroots was associated with increased cover of rocks and exposure to wind, and with decreased slopes and cover of forbs. Digs by grizzly bears were associated with the presence of biscuitroots, proximity to edge of forest, and increased cover of rocks. Results were consistent with previously observed tendencies of grizzly bears to concentrate their feeding within 50-100 m of cover. Key words: Ursus arctos, grizzly bears, biscuitroots, habitat selection, optimal foraging, Yellowstone National Park

A study designed to understand the spatial interactions among grizzly bears in northwest Montana is presented. A number of grizzly bears in the Swan Mountain Range, MT, were captured, classified and radiotagged, and the size of their home range was evaluated. It was found that the home ranges of adult females was smaller than those of subadults, while that of the adult males was larger. Home range overlap was more significant in subadult males and adult females. Habitat conditions, home range size and demography was found to influence the size and overlap of home ranges.

We documented one instance of an adult male grizzly bear preying upon a black bear and four instances where circumstantial evidence suggested that grizzly bears (two cubs-of-the-year, one yearling female that was injured, and one adult male) had been preyed upon by conspecifics. We also examined feces of grizzly bears for bear remains. Remains of bears tended to be more common in spring feces and did not differ in frequency between early and late years of the study. Our observations generally support existing hypotheses concerning cannibalism among bears.