Bears are classified as omnivores or carnivores, but nearly all species readily consume carrion (dead animals). Scavenging is a frequent and important behavior across many bear populations, providing a reliable source of protein and fat that supplements their varied diets. This opportunistic strategy allows bears to maximize caloric intake throughout the year, especially when other food sources are scarce.
The Role of Carrion in Bear Diets
Scavenging dead animals is an energetically efficient strategy for bears. A large carcass, such as a winter-killed elk or deer, provides concentrated calories without the energy expenditure or injury risk associated with hunting. This is particularly valuable in early spring after bears emerge from hibernation, helping them quickly replenish lost body mass. Carrion is a rich food source, especially important during the fall period known as hyperphagia, when bears consume massive amounts of food to build fat reserves for winter. Bears in environments lacking consistent vegetation and fish rely heavily on this found protein.
Scavenging Behavior by Species
The frequency and intensity of scavenging vary significantly among bear species, reflecting their size, dominance, and ecological niche.
Grizzly Bears
Grizzly bears (brown bears) are dominant scavengers. Their immense size and strength allow them to regularly engage in kleptoparasitism—stealing a kill from another predator, such as a wolf pack or mountain lion. For a grizzly, usurping a freshly killed ungulate is often more profitable than hunting itself.
Black Bears
Black bears are more opportunistic and less dominant scavengers. While they readily consume carrion, their diet focuses more on vegetation, insects, and smaller prey. They are less likely to confront large predators over a carcass and often retreat if threatened by a grizzly or wolf pack. Although they scavenge large prey like ungulates or marine mammals, these events are less central to their overall diet compared to grizzlies.
Polar Bears
Polar bears, the most carnivorous species, rely on marine mammal carcasses when hunting seals is not feasible. When sea ice retreats in the summer, they are forced onto land and become dependent on washed-up remains. Scavenging large whale carcasses, such as bowhead or gray whales, provides a massive food source that can sustain dozens of bears for weeks. Polar bears often consume only the energy-dense blubber and abandon the rest of the carcass.
Locating and Protecting Carcasses
The primary tool a bear uses to locate a dead animal is its extraordinary sense of smell. A bear’s olfactory bulb, the area of the brain responsible for processing scents, is about five times larger than a human’s, giving them a sense of smell estimated to be over 2,000 times more sensitive than ours. This acute sense allows them to detect decaying matter from miles away, particularly if the carcass is upwind. Black bears have been tracked traveling several miles in a straight line toward a dead animal, demonstrating the efficiency of their nose as a foraging mechanism.
Once a bear secures a large carcass, it often exhibits “caching” behavior by burying the remains. This involves covering the food with dirt, leaves, or snow to deter other scavengers and slow decomposition. Caching is most frequently reported in brown bears and preserves the large food source for subsequent meals over several days. A bear protecting a cached carcass is highly territorial and aggressive, and this is one of the primary contexts for unexpected and dangerous human encounters.