Habitat, Movement, Dispersal,
Home Range, and Space Use

Brown bear home ranges

Brown bears occupy home ranges, or an area where the bear lives and obtains its resources. Unlike territories of group-living species, these areas are not defended and commonly overlap with the home ranges of other individual bears (1). Nevertheless, it is interesting to note that there are areas that seem to be occupied quite exclusively by closely related individuals (2). Adult home range size across the entire bear ‘active period’ (approximately May through September) was preliminarily evaluated in 2003 using VHF technology (1). These results suggest that, in general, average home range size was greater in the north compared to the south (1). Adult male home ranges were larger than adult females’, while solitary female home ranges were larger than those of females with yearlings or females with cubs of the year (see Table) (1). Similarly, subadult males also have larger home ranges than subadult females (3). These home ranges are generally larger than those reported from central and southern Europe, for example Romania (4), Bulgaria (5), Croatia and Bosnia and Herzegovina (6), and Spain (7), but are similar to home range sizes reported for bears in boreal forests in North America (1). Variation in home range size during summer only (May-August) was more recently explored using GPS data in 2019 and the findings are put into context below (8). While the estimates provided below are a general guideline for bear home range size in Scandinavia, it is important to understand that the home range size of individual bears can vary widely depending on their reproductive status and environment, e.g., habitat quality, food availability, bear population density, season, and human disturbance.

Factors affecting bear home range size include:

Female reproductive status: Female with cubs of the year generally have smaller home ranges than solitary females or females with yearlings (see Table) (1, 9). Newborn cubs are small and have limited mobility which likely restricts the mothers’ movements directly after den emergence. The home range size of females with cubs of the year slowly increases throughout the rest of the season after the risky mating period ends and as the cubs become more mobile (8, 9). Females with larger cubs and solitary females have comparatively larger home ranges (1).

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Mating season: Adult males increase their range during mating season (May-June), when they roam broader areas in search of females (8). For example, a recent report shows that mean adult male home range size was 865 and 1022 km2 in May and June, which then decreased to 725 and 547 km2 in July and August (8). Like males, solitary females increase their range size during the mating season while in search of mates, although their range size is still small compared to males (190 and 266 km2 in May and June and 167 and 151 km2 in July and August) (8). On the other hand, females with cubs of the year restrict their ranges during mating season to avoid contact with infanticidal males (10), which is an important cause of cub mortality (9).

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Food availability: Food availability is often a primary driver of brown bear home range size with the general rule being that a high amount of food decreases home range size, while less food increases home range size. Although this is likely true to some extent in Scandinavia, we find little evidence for this. For example, bear home range size does not increase during years with low berry production, their primary fall food source, as might be expected (11). This is likely because there is a relatively continuous distribution of berries across the Scandinavian landscape. This indicates that bears are not very food limited during the hyperphagia season in Scandinavia (11). An earlier study from 2006 also found that subadult home range size was not linked to variation in local food condition, which is intuitive as dispersing bears would likely not be limited by food availability (3). However, this should be interpreted with caution as climate change may create greater swings in berry and other food availability which may affect bear home ranges in the future.

Population density: In general, a high bear population density can lead to smaller home ranges as bears compete for limited resources. This is true in Scandinavia, where we observed that home range size estimates for both sexes and age classes (male/female and adult/subadult) of bears in the south decreased as local bear density increased (1, 3).

Habitat quality and human disturbance: The type and quality of available habitat can also play a significant role in bear home range size. As described below, bears in Scandinavia generally prefer rugged forested terrain and avoid human‐related infrastructure (12). Human activities, such as logging, road construction, and recreational activities may degrade habitat and lead to larger home ranges as bears move to avoid these disturbances, but this remains unknown.

Habitat selection and space use

The majority of what we know about bear habitat selection in Scandinavia comes from the Southern Study Area. At a broad scale, bears in Scandinavia primarily dwell in the boreal forest, largely preferring rugged forested terrain compared to flatter forested terrain and bogs. However, it is important to understand that the types of habitats bears use is driven by both human activities as well as the time of day and seasonal pulses of different foods.

Factors affecting bear habitat selection and space use include:

Time of day: Habitat selection naturally varies between resting periods (when bears seek cover) and active periods (when bears are foraging for food). In general, bears choose habitats with relatively dense vegetation and limited visibility when they rest, especially during daytime and in summer, when there is more human activity in the forest (13). For example, when resting during the day, bears are more likely to use dense patches of forest or forested bogs and avoid open areas such as clearcuts (14). When they are active during the morning and dusk, however, they use habitats that provide access to food resources.

Seasonal food availability: Bears use habitats differently at different times of year and in a way that coincides with the availability of seasonal food sources. For example, during the spring ungulate birthing period when bears prey on both newborn moose and/or reindeer, bears use habitats where they are more likely to find newborn calves. Bears in Scandinavia primarily prey on newborn moose and, during the birthing season, they use areas closer to old clear cuts and deciduous forests; moose commonly use deciduous forests during the birthing period (15). With bears that overlap reindeer areas in Scandinavia, they generally use more rugged terrain, closer to wetlands and coniferous forests during this period where they are more likely to find reindeer with newborns (15). During the prime berry season, on the other hand, bears move to areas with either high probability of blueberry occurrence and high abundance, or a high probability of lingonberry abundance, which generally included mature or missed forests or clear cuts (14, 16).

Reproductive status and individual variation: The choice of resting area also differs between females according to their reproductive status. For example, compared to solitary females, females with cubs of the year rest in habitats that have more open vegetation, i.e., tall dense forest with more tall pine trees and fewer spruce and broadleaved trees (17). These tall trees are excellent for cubs to climb to avoid danger, thus this choice of habitat is likely a strategy to avoid infanticide from male bears during the mating period (17). We also see consistent individual variation in habitat selection among brown bears. For example, when controlling for availability of the habitat, some bears are more likely to use boggy areas and clear cuts than others (18).

Human disturbance: Like other large carnivores in Scandinavia, bears generally avoid areas with a lot of human activity and human‐related infrastructure including cities, towns and cabin fields, houses, and roads (especially large roads) (14, 18, 19) although there are exceptions to this. They also alter their fundamental behavior when they are in closer proximity to humans (12, 13, 20, 21) For more details on the effects of human disturbance on habitat selection and space use see Human disturbance and brown bear behavior.

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Movement and Dispersal

Movement and circadian rhythm: Bears in Scandinavia are generally the most active during two different time periods over the course of a day – early in the morning (~400-800) and during the evening/night (~1800-2200) (22). However, how far they move and how much they move can vary depending on their age, sex, and the season. For example, males tend to move greater distances than females (1), a pattern that is even more pronounced during the mating season (8). Females also change their movement patterns based on season. For example, they tend to be relatively inactive right after they emerge from their den, with short active periods during morning and evening (22). Activity picks up after that and remains high during the mating, post-mating, and hyperphagia periods (22). Females with cubs of the year tend to move more during the daylight hours right after den emergence and during the mating season, compared to other females, likely in an attempt to avoid infanticide (22). During the mating season, however, solitary females in estrous will travel farther than at other times of the year, likely in search of mates. This period also coincides with the spring predation period, however, and it is possible that females travel further during this time to increase the chances of running into newborn moose, not just to maximize the chances of finding mates. Bear movement patterns can also be affected by humans and in general, bear movements generally peak in the hours without outdoor human activity (23). For example, bears move most in the nocturnal and twilight hours and less during daytime in areas with higher road density compared to more roadless areas (24).

Dispersal and resettlement: Dispersal is defined as an animal leaving the home range of their mother (i.e., their natal home range), traveling a certain distance, and settling their own home range. In general, male bears are more likely to disperse than females. Data from the Northern and Southern Study Areas in Scandinavia showed that 32% (N) and 46% (S) of females and 81% (N) and 92% (S) of males dispersed before reaching the age of 5 (25). Furthermore, males have a 94% probability of leaving their natal home range, while females only have a 41% probability (26). The majority of males disperse when they are two years old, while the majority of females disperse when they are three (25). Male dispersal often occurs within a single year whereas female dispersal may occur over multiple years (25). Males also tend to move further away from their natal home ranges than females (see graph). For example, the longest dispersal distance recorded was 90 km for females and 467 km for males (25).

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The likelihood that a bear disperses, and how far they eventually go, can be affected by a number of factors other than sex. For example, high local bear density increases the likelihood that a bear will disperse as well as the eventual distance they travel. This implies that bears in northern Scandinavia, where bear density is lower, are less likely to disperse. Bears in the southern Scandinavia population, on the other hand, are more likely to disperse and also tend to move further away (25). At the family-unit level, competition between parents and siblings can also drive dispersal patterns. For example, daughters settled twice as far away from their natal range when their mother was alive compared to when she was dead (27). A type of ‘dominance hierarchy’ among female siblings from the same litter, which is based on body size, may cause the subordinate sisters to disperse (26). The presence of human-related disturbance has also been shown to affect dispersal movement patterns in male bears (28).

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The dispersal and resettlement patterns of bears is important to understand because these patterns affect population range expansion and internal and external connectivity, i.e., connectivity within Scandinavia’s three subpopulations and connectivity with other populations such as those in Finland and Russia. Internal and external population connectivity affects gene flow, and therefore the genetic health of the population (29, 30). Bear dispersal patterns should be continuously monitored due to their important effect on the population’s expansion front, connectivity, and genetic health.