General Bear
Characteristics and Behavior

Characteristics

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Scandinavian brown bears are robust, sturdy animals with a strong neck and jaws, round, prominent ears, and a noticeable hump over their shoulders; the hump is composed of powerful muscles that assist them with activities such as digging. The color of their fur varies, ranging from light to dark brown, while individual bears can have different shades of fur, and some may appear almost black or exhibit a lighter, almost blonde coloration. Bear cubs often have a distinctly bright collar that is lost as they age.

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Brown bears have a distinctive facial profile with a prominent snout. Their eyes are relatively small compared to the size of their head. Brown bears eyesight is not as acute as their sense of smell, which they use to detect food and navigate their environment. Bears have strong, long, non-retractable claws that aid in foraging. Their hindfoot makes a track similar to that of a human foot, while the front paw leaves a track that is wider and shorter. Foot size, and therefore track size, vary in relation to body size, while track size can also vary based on the substrate. In general, it is only possible to differentiate between large males (mean front pad = 14 cm; mean back pad = 22.3 cm) and small subadult females (2-3 years old; mean front pad = 10.3 cm; mean back pad = 17.3 cm); track sizes from all other age classes and sexes overlap (1). Bears have teeth that are well-suited for their omnivorous diet, possessing sharp canines for tearing meat and molars for grinding plant material. Over time, the teeth of older bears often show signs of wear due to years of use.

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In Scandinavia, adult males typically weigh between 150 to 350 kg or more (mean = ~250 kg), while adult females are generally smaller, ranging from 80 to 200 kg (mean = ~150 kg) (2). They reach peak body mass at around 7 to 8 years old (2). The large variation in size makes it functionally impossible to distinguish between solitary male and female bears in the field. Interestingly, bears in Scandinavia appear to gain mass during spring compared to bears in southern Europe (Dinara Mountains) which lose mass post hibernation (2). This is perhaps due to the greater availability and use of protein-rich food in Scandinavia during spring (2).

General behavior

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Solitary nature: Scandinavian brown bears are typically considered solitary animals (i.e., nonsocial), especially males. Females seem to be slightly more social than males; adult females have been observed moving together for short periods of time (SBBRP observation). Otherwise, males and females associate during the breeding season, and of course females associate with their cubs during the rearing process. For more details on social and individual behavior see Diet and foraging.

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Communication: Bears use a mixture of vocalizations, body language, and scent marking to communicate with each other. Huffing or low growling sounds are used to assert dominance or warn of aggression when stressed. Stressed bears will also pop their jaws which makes a unique popping sound. Body language also plays a key role in communication. For example, when aggravated or threatened, bears may charge forward and/or stomp on the ground with their front legs and paws. Standing up, however, is generally done to increase their viewshed, rather than used as a warning. Marking behavior, including biting, scratching, stripping bark, and rubbing trees/other objects with their back, shoulders, and head, and scent-marking by urinating at  the base of rub trees, is a key form of communication between bears as it can transfer information to others without direct interaction (3-5). Visual signaling (signs that bears can see) can provide information about whether another bear was present (4), while information conveyed by scent marking (signs that bears can smell) includes individual identification including sex as well as information about reproductive status (3).

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Home ranges: Brown bears are not territorial (i.e., they do not actively defend an area), but rather have overlapping home ranges (6). Males have larger home ranges than females, while female home range size is dependent upon their reproductive status. In other words, females with cubs of the year have smaller home ranges (small cubs are less mobile and more vulnerable), while females with larger cubs and solitary females have comparatively larger home ranges (6). Both females and males will disperse from their natal home range (i.e., their mothers home range), but males disperse more often (7). For more details on what affects home range size see Habitat, movement, dispersal, home range, and space use.

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Movement and activity: Brown bears are generally crepuscular animals, meaning they are most active during dawn and dusk. However, their activity patterns are flexible and vary between individuals, which means they can be active during other parts of the day and night (8). Bears may also be more active at different times of the day depending on the availability of prey or the level of human disturbance (8, 9). For example, bears move more during the night and twilight hours and less during the daytime in areas with more human disturbance (e.g., higher road density; 9). Regardless of the time of day they chose to be active, brown bears are efficient travelers and can move quickly over long distances. Bears are also proficient swimmers and can easily cross bodies of water, including lakes and rivers. For more details on bear movement and activity patterns see Habitat, movement, dispersal, home range, and space use.

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Mating, reproduction, and cub rearing: Brown bears have a polygamous mating system, meaning males mate with several females and females with several males. In Scandinavia, brown bear mating season typically occurs between May and June. Mean age at primiparity for females (i.e., the age that females reproduce for the first time) was estimated at 4.7 (south) and 5.3 (north) years old and ranged between age 4 and 7 (10, 11). Female brown bears have delayed implantation, meaning fertilized eggs remain dormant in the uterus for about five months, prior to implantation in November–December (12). The gestation period is around 6 to 8 months and females give birth to cubs in the den typically between January and March, with an average litter size of about 2.4 (range = 1 to 4) cubs (12, 13). In Scandinavia, female bears care for their cubs for between one and half to two and half years, after which the cubs move away from the female and the female may reproduce again (12, 14). Infanticide is relatively common in the bear population, with males killing young cubs likely to induce the female into estrous sooner (15, 16). For more details on mating, reproduction, and fitness see Mating, reproduction, and fitness.

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Diet: Brown bears are opportunistic omnivores with a highly varied diet that changes seasonally (17). In general, they feed on vegetation, including berries, grasses, roots, fungi, and protein in the form of insects, small mammals, ungulates, and other carrion. Bears are efficient predators of newborn ungulates (e.g., moose and reindeer calves; 18, 19, 20) and are also effective scavengers (21), but only rarely kill adult ungulates (22). During spring and summer, bear diet in Scandinavia is predominantly made up of moose (i.e., newborn calves) and ants (Formica spp. and Camponotus herculeanus) (17, 23). During autumn, berries dominate the diet; the most important are bilberry (Vaccinium myrtillus), followed by crowberry (Empetrum hermaphoditum), and then lingonberry (Vaccinium vitis-idaea). Research suggests the proportion of berries in fall diet is stable between years, but the relative importance of the species varies (i.e., bears switched to crowberries when bilberries were less abundant; 17). For more details on the diet of the Scandinavian brown bear population see Social and individual behavior and intraspecific interactions.

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Denning and hibernation: Scandinavian brown bears hibernate during winter when they remain dormant for several months relying on stored fat for energy. During fall, bears enter into what is known as hyperphagia which is characterized by increased appetite and behavioral changes that help them gain fat reserves before entering hibernation (24). During hibernation, bear’s metabolic rate significantly decreases, leading to a lowered body temperature, heart rate, and respiration rate, and they remain inactive, ingesting no food or water (25). Bears hibernate in dens, of which the most common type in Scandinavia’s southern bear population are made from excavated abandoned anthills (26). Bears also use dens in rock crevices or caves, and between or under boulders and, in rare cases, they use open dens that are made from branches, plants, and moss piled to form something resembling a large nest (26). In Scandinavia, the mean date of den entry is 27 October (5 October-18 November) for males (26) and 28 October (24 September-20 November) for females (27), while mean date of den emergence is 4 April (6 March–25 April) for males (26) and 20 April (6 March–14 June) for females (27). Hibernation can last up to 6 to 7 months in Scandinavia, with females remaining in the den longer than males, and pregnant females staying in the longest (26). For more details on denning and hibernation see Section 6.

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Tolerance towards humans: Brown bears can exhibit varying levels of tolerance and aggression towards humans depending on the ecosystem. In Scandinavia, however, bears tend to be unaggressive and avoid people (28-31). When bears were approached by humans in a series of approach studies performed by the SBBRP, the animals either moved away immediately or stayed in place and hid; no bears ever exhibited aggressive behavior towards humans when approached (28-31). That being said, bears can act aggressively towards humans and injuries and even fatalities can occur, particularly when hunting bears (32). For more details on human-bear interactions see The effects of hunting on the population, behavior, and evolution.

References

1. Mattisson J, Støen O-G, Kindberg J. Bjørnens vandring og områdebruk - Forskjeller mellom kjønn, aldersgrupper og sesong. Norsk institutt for naturforskning; 2019.

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2. Swenson JE, Adamič M, Huber D, Stokke S. Brown bear body mass and growth in northern and southern Europe. Oecologia. 2007;153:37-47.

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3. González-Bernardo E, Bagnasco C, Bombieri G, Zarzo-Arias A, Ruiz-Villar H, Morales-González A, et al. Rubbing behavior of European brown bears: Factors affecting rub tree selectivity and density. Journal of Mammalogy. 2021;102(2):468-80.

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4. Penteriani V, González-Bernardo E, Hartasánchez A, Ruiz-Villar H, Morales-González A, Ordiz A, et al. Visual marking in mammals first proved by manipulations of brown bear tree debarking. Sci Rep-Uk. 2021;11(1):9492.

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5. Jojola SM, Rosell F, Warrington I, Swenson JE, Zedrosser A. Subadult brown bears (Ursus arctos) discriminate between unfamiliar adult male and female anal gland secretion. Mammalian Biology. 2012;77(5):363-8.

6. Dahle B, Swenson JE. Home ranges in adult Scandinavian brown bears (Ursus arctos): Effect of mass, sex, reproductive category, population density and habitat type. Journal of Zoology. 2003;260(4):329-35.

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10. Zedrosser A, Dahle B, Støen O-G, Swenson JE. The effects of primiparity on reproductive performance in the brown bear. Oecologia. 2009;160:847-54.

11. Zedrosser A, Bellemain E, Taberlet P, Swenson JE. Genetic estimates of annual reproductive success in male brown bears: The effects of body size, age, internal relatedness and population density. Journal of Animal Ecology. 2007;76(2):368-75.

12. Steyaert SM, ENDRESTØL A, Hacklaender K, Swenson JE, Zedrosser A. The mating system of the brown bear Ursus arctos. Mammal review. 2012;42(1):12-34.

13. Bischof R, Bonenfant C, Rivrud IM, Zedrosser A, Friebe A, Coulson T, et al. Regulated hunting re-shapes the life history of brown bears. Nature Ecology & Evolution. 2018;2(1):116-23.

14. Dahle B, Swenson JE. Factors influencing length of maternal care in brown bears (Ursus arctos) and its effect on offspring. Behavioral Ecology and Sociobiology. 2003;54:352-8.

15. Bellemain E, Swenson JE, Taberlet P. Mating strategies in relation to sexually selected infanticide in a non‐social carnivore: the brown bear. Ethology. 2006;112(3):238-46.

16. Steyaert SM, Swenson JE, Zedrosser A. Litter loss triggers estrus in a nonsocial seasonal breeder. Ecology and evolution. 2014;4(3):300-10.

17. Stenset NE, Lutnæs PN, Bjarnadóttir V, Dahle B, Fossum KH, Jigsved P, et al. Seasonal and annual variation in the diet of brown bears (Ursus arctos) in the boreal forest of southcentral Sweden. Wildlife Biology. 2016;22:107-16.

18. Swenson JE, Dahle B, Busk H, Opseth O, Johansen T, Soderberg A, et al. Predation on moose calves by European brown bears. Journal of Wildlife Management. 2007;71(6):1993-7.

19. Rauset GR, Kindberg J, Swenson JE. Modeling female brown bear kill rates on moose calves using global positioning satellite data. Journal of Wildlife Management. 2012;76(8):1597-606.

20. Støen O-G, Sivertsen TR, Tallian A, Rauset GR, Kindberg J, Persson L-T, et al. Brown bear predation on semi-domesticated reindeer and depredation compensations. Global Ecology and Conservation. 2022;37:e02168.

21. Tallian A, Ordiz A, Metz MC, Milleret C, Wikenros C, Smith DW, et al. Competition between apex predators? Brown bears decrease wolf kill rate on two continents. P Roy Soc B-Biol Sci. 2017;284(1848).

22. Dahle B, Wallin K, Cederlund G, Persson IL, Selvaag L, Swenson JE. Predation on adult moose Alces alces by European brown bears Ursus arctos. Wildlife Biology. 2013;19(2):165-9.

23. Swenson JE, Jansson A, Riig R, Sandegren F. Bears and ants: Myrmecophagy by brown bears in central Scandinavia. Can J Zool. 1999;77(4):551-61.

24. Fuchs B, Yamazaki K, Evans AL, Tsubota T, Koike S, Naganuma T, et al. Heart rate during hyperphagia differs between two bear species. Biology Letters. 2019;15(1):20180681.

25. Stenvinkel P, Fröbert O, Anderstam B, Palm F, Eriksson M, Bragfors-Helin A-C, et al. Metabolic changes in summer active and anuric hibernating free-ranging brown bears (Ursus arctos). PloS one. 2013;8(9):e72934.

26. Manchi S, Swenson JE. Denning behaviour of Scandinavian brown bears Ursus arctos. Wildlife Biology. 2005;11(2):123-32.

27. Friebe A, Swenson JE, Sandegren F. Denning chronology of female brown bears in central Sweden. Ursus. 2001;12:37-45.

28. Ordiz A, Moen GK, Sæbø S, Stenset N, Swenson JE, Støen O-G. Habituation, sensitization, or consistent behavioral responses? Brown bear responses after repeated approaches by humans on foot. Biological conservation. 2019;232:228-37.

29. Moen GK, Ordiz A, Kindberg J, Swenson JE, Sundell J, Støen O-G. Behavioral reactions of brown bears to approaching humans in Fennoscandia. Écoscience. 2019;26(1):23-33.

30. Ordiz A, Støen OG, Sæbø S, Sahlén V, Pedersen BE, Kindberg J, et al. Lasting behavioural responses of brown bears to experimental encounters with humans. Journal of Applied Ecology. 2013;50(2):306-14.

31. Moen GK, Støen O-G, Sahlén V, Swenson JE. Behaviour of solitary adult Scandinavian brown bears (Ursus arctos) when approached by humans on foot. PloS one. 2012;7(2):e31699.

32. Støen O-G, Ordiz A, Sahlén V, Arnemo JM, Sæbø S, Mattsing G, et al. Brown bear (Ursus arctos) attacks resulting in human casualties in Scandinavia 1977–2016; Management implications and recommendations. PloS one. 2018;13(5):e0196876.