Bears and their Influence
on the Environment

Bears as apex predators

 

An apex predator is a species at the top of a food chain that has no natural predators, preying on other species without being preyed upon itself. Large carnivores, including brown bears, can therefore play an important role in ecosystem function through the direct and indirect effects of predation; direct effects include directly decreasing the number of prey on the landscape through predation, while indirect effects include shifting prey behavior. Also known as ‘top down control’, these shifts in prey behavior and population size can have trickle down effects within the ecosystem, generally via the altered or decreased foraging of plants by the prey species, which can subsequently affect a wide range of other plant and animal species.

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The baseline ecosystem that bears live in in Scandinavia is primarily driven by human activities, ranging from large-scale forestry, agriculture and farming, villages, roads, and other infrastructure. Forestry is a prime example of this, with forestry practices in Scandinavia indirectly increasing the moose population by providing more forage than would otherwise be on the landscape. On the other hand, the annual moose hunt in Scandinavia has the opposite effect and helps to control or decrease the moose population. Bears are also hunted, which can affect both the population size as well as their fundamental behavior. Hunted carnivores also behave differently (see The effects of hunting on the population, behavior, and evolution for more details) which may alter predation patterns and indirectly affect moose population dynamics (1). In Scandinavia our research suggests that the brown bears functional role as an apex predator is likely dampened by anthropogenic effects in a variety of ways (1, 2). For example, the combination of human-driven alterations to the forest landscape, moose management and harvest practices, and the altered behavior of the hunted bear population means humans likely usurp top down control from the bear population, and that bears are only one small portion of what drives moose population dynamics and the subsequent effects those have on the ecosystem in Scandinavia.

 

Predation on ants

 

Red wood ants (Formica rufa) are an anthill building keystone species in the Scandinavian forests, meaning they have a large impact on their ecosystem through nutrient cycling, seed dispersal and removal, and their predation on other invertebrates (3). Ants are an important part of brown bear diet in Scandinavia, and they consume them the most during spring and summer period (4, 5). Interestingly, bear predation on ants may have a cascading effect on ecosystem function in ways we still do not yet understand. For example, anthill size is an indicator of ant numbers, and we know that anthills are smaller in areas with a high density of bears compared low bear density (6). However, the effect of bears is yet again tampered down by humans; even in areas with high bear density, anthill sizes are larger near human settlements that bears avoid (6).

 

Bears and plants

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There is some evidence that bears may affect plant dynamics in the Scandinavian forests by eating, passing, and spreading berry seeds in their feces. For example, a recent study in 2019 found that berry seeds suffered no damage when passing through a bear’s gut (7). Furthermore, seeds that were still encased in the berry (i.e., did not pass through the bear) germinated almost one month later than seeds that were releases from the fruit (e.g., seeds that had passed through the bear) (7). Thus, alongside the other forest animals that rely on berries, bears in Scandinavia may facilitate blueberry seed dispersal and germination (7).