Bears are large terrestrial carnivores and omnivores that occupy a high position in their ecosystems. Their size, powerful musculature, and defensive aggression allow them to dominate most interactions with other wildlife. A healthy adult bear, such as a Polar bear or Kodiak brown bear, rarely faces a natural threat other than humans. The question of what animals eat bears is complex, shifting dramatically based on the bear’s age, size, health, and location. While healthy adults are largely invulnerable, younger or deceased bears provide sustenance for a wide range of animals.
Predators of Bear Cubs and Juveniles
Cubs and subadults are the most common targets for predation across all bear species, as their vulnerability is inversely proportional to their age. The primary defense for a cub is the presence of its mother, forcing predators to rely on speed and stealth to separate the offspring. North American predators include coordinated pack hunters like gray wolves, which distract the mother while others target the cub. Solitary ambush predators, such as mountain lions and cougars, strike quickly at isolated cubs before the mother can react.
Larger raptors, specifically Golden Eagles, also pose a threat to the smallest cubs or yearlings. However, the most significant threat comes from infanticide by adult male bears. This behavior is a reproductive strategy where a male kills unrelated cubs to induce the female to re-enter estrus, allowing him to mate. Infanticide can account for a considerable portion of cub mortality, sometimes up to 45% in brown bear populations. The size disparity makes this intraspecific predation an effective mechanism of population control.
Rare Predation of Adult Bears
Predation on a healthy adult bear is rare, requiring massive size, superior hunting coordination, or environmental advantage. The Siberian (Amur) tiger is one of the few predators capable of regularly hunting and killing adult bears, including Asiatic black bears and Ussuri brown bears, in their overlapping range. Bear remains can constitute a measurable portion of the tiger’s diet, sometimes up to 10% in localized areas. The tiger relies on a stealthy ambush, targeting the bear’s spine or throat with a precise bite before the bear can use its strength in a direct confrontation.
In North America, a large, coordinated wolf pack can occasionally bring down a smaller adult bear, usually black bears or subadult brown bears. Wolves rely on numbers and endurance to exhaust and harass the bear, inflicting debilitating injuries. Intraspecific predation also occurs among adults; larger, dominant male bears sometimes kill and consume smaller bears, typically females or subadults, in territorial disputes. Additionally, the larger grizzly bear is a known predator of the smaller American black bear, especially when the black bear leaves dense forested areas. These fatal encounters are usually predicated on specific circumstances, such as the victim being injured, old, or surprised, rather than routine hunting.
Scavenging Bear Carcasses
The distinction between active predation and scavenging is crucial, as a far wider range of animals will consume a bear’s carcass than will actually kill one. Once a bear dies from natural causes, injury, or is killed by a vehicle, its body becomes an important source of sustenance. This ecological cleanup is performed by mammals and birds that cannot hunt a live bear.
In the Arctic and sub-Arctic regions, scavengers include the Arctic fox, which often follows polar bears, along with gulls, hawks, and wolves. In forested regions, smaller carnivores such as wolverines, coyotes, and foxes consume the remains. Birds, including ravens, crows, and vultures, are often the first to locate a carcass due to their keen sense of smell and aerial vantage point. These scavengers play a necessary role by consuming carrion and preventing the spread of pathogens.