Human Disturbance and
Brown Bear Behavior

Like most large carnivores, brown bears require a lot of space to fulfill their biological needs. Although the number of people living in the rural Scandinavia has been declining, the number of roads and amount of infrastructure has remained steady or increased. This includes a wide network of forestry roads and activities and the construction of new recreational cabins, cabin fields, and recreational areas, especially around national parks. The brown bear population has functionally recovered in Scandinavia (1) after a period of steady growth, and exists alongside human development and activities. Although bears could benefit from human activities in some ways, e.g., via scavenging on hunter-killed remains, any close proximity to humans or the use of human-derived resources may create problems for both bears and people. Brown bear behavioral responses to human disturbance and other anthropogenic pressures might lead to indirect habitat loss, decreased ability to forage, and lower reproductive success (2). These effects could ultimately have population-level consequences (2). Thus, it is important to understand how the presence of people and the associated infrastructure affects bear behavior and thereby potentially affect population dynamics.

Activity patterns, movement, and habitat use

Brown bears generally avoid encounters with people (3) and exhibit a physiological stress response to humans; i.e. they are more stressed when they are near human settlements (4). Like other large carnivores in Scandinavia, bears typically avoid areas with high human activity and human‐related infrastructure including cities, towns and cabin developments, houses, recreational areas, and roads (5-8). Bears also become more nocturnal in response to human disturbance, avoiding human presence during daylight hours (9). Although some bears may use smaller roads to facilitate movement, for example during mating season (10), roads are usually an impediment to bear movement in Scandinavia which may ultimately affect bear behavior, dispersal, and gene flow and (11). In areas where there are many roads, bears also tend to be more nocturnal and move more often during the dark and twilight hours compared to more roadless areas (12). In general, bears also tend to select daytime bed sites in denser vegetation that offers concealment when they are close to human settlements (3).

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The summer/fall seasons are particularly busy in the forests of Scandinavia when people are out hunting and collecting berries. Bears are hunted in Scandinavia (see The effects of hunting on the population, behavior, and evolution), but bear hunting is not the only type of hunting activity that bears respond to. Moose hunting occurs during fall and evidence suggests that this creates a ‘landscape of fear’ that bears respond to by avoiding areas with high moose hunting activity (2). Mortality risk was greater for bears that selected higher-risk areas than those that selected low-risk areas when foraging for bilberries during the hunting season (13). During summer and fall bears are more likely to select places on the landscape that offer more concealment, such as young regenerating coniferous forests, as well as areas further away from roads and human access (2, 3). Day beds tend to be the most concealed during this time of year (3).

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Female bears tend to use areas within their home range that offer high-quality food while also avoiding the risk of human disturbance (14). For example, female bears generally avoid disturbed areas and select for more rugged terrain (or steeper slopes) during times when human activity in the forest is high, such as summer and fall (14). However, not all female bears avoid human areas. During the spring mating season, females with cubs of the year use areas that are less rugged and more open as well as closer to humans (15). This creates a type of ‘human-shield’ effect whereby females with cubs of the year trade off potential disturbance from people in order to avoid infanticidal males and decrease their chances of losing their cubs (16). Females who lose their cubs prior to or during mating season move away from human areas, apparently no longer needing to make that trade-off (17).

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Male bears also seem to respond to human activity in different ways depending on their life stage, for example whether they are a resident with a home range or in the dispersal phase (10). Resident males avoid areas that are near buildings or large public roads, but they used smaller forestry roads to facilitate their movements, i.e., they moved through the landscape faster when they were near smaller roads (10). Dispersers, on the other hand, only avoid human infrastructure moving through the landscape, likely because they were unfamiliar with the terrain in front of them and unable to avoid it on a broad scale (10).

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When directly approached by people, bears tend to either flee or hide (18-20). Well hid bears may stay in their hideout if the people pass more than approximately 100 m away; if people come closer bears move away silently and often unnoticed by the people to avoid encounters. However, both these types of encounters affect the bears behavior in the days following the event. For example, following encounters with people, bears that flee move on average 1 km away, and then reduce their movements after reaching a different location (18, 21). Bears also alter their foraging and resting routines from about 2 days and up to a week after the encounter occurred, moving more during the nighttime and less during the daytime than normally, presumably to avoid encountering humans again (19, 21).

Foraging behavior

Human alteration of habitat, especially through forestry practices, can change the availability of food and brown bear foraging patterns. For example, ants are more prevalent in clear cuts, which bears select for in order to utilize that resource (22). Forestry practices also have a large effect on berry occurrence and abundance, resulting in brown bears foraging more in mature forests and clearcuts where berries occur more often and in greater abundance (23). Unlike in North America, bears in Scandinavia do not generally approach human settlements to obtain anthropogenic food sources; bear diets are generally the same whether they are near settlements or in more remote areas (24).

Mating and reproduction

It is possible that human disturbance could disrupt normal mating behaviors and interactions between bears. For example, females with dependent young select areas near humans, presumably to avoid potentially infanticidal males; this is commonly called the ‘human shield effect’ (16). Consequently, female bears that select for more human-related areas increase the probability that their cubs survive (16). Additionally, females who remain with their offspring an additional year (until they are 2 ½) tend to use areas closer to buildings and towns while males tend to avoid these areas (25). Again, this is possibly due to a human shield effect, meaning females may use these areas to avoid interactions with males during mating season that might result in them weaning their cubs (25).

Denning behavior

Bears also tend to select their dens in a way that avoids potential human disturbance. In general, brown bears select den sites at least 2 km from infrastructure with regular human activity, e.g., main roads and buildings (26). Bears in Scandinavia also tend to select dens that are more concealed and in more difficult to access terrain when the potential for human disturbance is higher, e.g., when they are closer to roads and villages (27). Furthermore, adult males tend to den further away from main roads and houses than other bears, suggesting they are less tolerant of human activities (28). It has been suggested that human activity around the den site is the main reason bears will abandon, or switch, dens in Scandinavia (29). Several studies have since demonstrated that bears select their den sites to reduce such risks of disturbance (28, 30). For example, abandoned dens are more likely to be located closer to plowed roads, which might increase the potential for human disturbance (28). Bear often abandon dens when people visit the area, especially if they visit early in the denning period or approach within 200 m of the den site (26, 31). It is not ideal, but not uncommon for bears to have to abandon the den and select a new one. The energy used to wake up and find and prepare a new den can decrease their body condition after den emergence as well as have fitness consequences. For example, of pregnant females that abandoned their dens, 60% lost cubs compared to only 6% of pregnant females that lost cubs and did not abandon their den (29).