Brown Bear

The brown bear is a single species with many faces — the grizzly of the Rocky Mountains, the salmon-fat giants of the Alaskan coast, the shy forest bears of Scandinavia and the Carpathians, and the Kodiak, the largest brown bear of all. Wherever it lives, it is the largest land predator in the region and a powerful shaper of its ecosystem.

Overview

Brown bears once ranged across most of the Northern Hemisphere. Persecution cleared them from much of Western Europe and the contiguous United States, but they remain widespread in Russia, Scandinavia, the mountains of southern Europe, Central Asia, western Canada, and Alaska. Today around 200,000 survive worldwide, roughly half in Russia.

Physical characteristics

Size varies enormously with food supply. An interior grizzly might weigh 150–250 kg; a coastal Alaskan or Kodiak bear gorging on salmon can top 600 kg and stand three metres tall on its hind legs. All brown bears share a distinctive shoulder hump — a mass of muscle that drives the forelimbs, making them superb diggers — long front claws, a dished facial profile, and small rounded ears.

Despite their bulk, brown bears can sprint at over 50 km/h, climb (young bears especially), and swim well.

Diet

Brown bears are omnivores, and most of their diet is plant matter: grasses and sedges in spring, roots and bulbs they dig up, and huge quantities of berries in late summer as they fatten for winter. They also eat insects — tearing apart logs and ant nests — scavenge carcasses, prey on newborn elk, moose, and caribou calves, and, along salmon rivers, catch spawning fish by the dozen. Bears that carry salmon carcasses into the forest fertilise the trees with marine nutrients, a link between ocean and forest.

Hibernation

In autumn a brown bear enters hyperphagia, eating up to 20 hours a day to add a thick fat layer, then digs a den — usually on a north-facing slope where snow will insulate it. Through the winter it enters torpor: heart rate down to as few as 8 beats per minute, metabolism roughly halved, no food, water, or waste elimination for months, yet muscle and bone barely wasting. Understanding how bears avoid the muscle loss and organ damage that would kill an inactive human is an active area of medical research.

Reproduction and life cycle

Brown bears breed in early summer, but development is delayed: the embryo only implants in autumn, and only if the female has stored enough fat. Cubs are born in the den mid-winter, tiny and helpless, and stay with their mother for two to three years — one of the longest periods of maternal care among land mammals. Females breed only every three or four years, so populations grow slowly.

Threats and conservation

Globally the brown bear is Least Concern and stable, but that hides a split picture. Large northern populations in Russia, Alaska, and Canada are secure, while small, isolated groups — the last few dozen bears in the Pyrenees or the Cantabrian Mountains, for example — are highly vulnerable. The main pressures everywhere are habitat fragmentation by roads and development, and conflict with people over livestock, beehives, and rubbish. Where bears are protected and given connected habitat, as in Scandinavia and the northern Rockies, they have recolonised former range.