The American Black Bear (Ursus americanus) is the most widespread bear species on the continent, ranging from Alaska and Canada down into central Mexico. They are highly adaptable omnivores that occupy diverse forested habitats, establishing themselves as near-apex predators. While a healthy adult black bear has few natural enemies, it is still vulnerable to predation, particularly during its early life stages.
The Primary Targets: Predation on Cubs and Juveniles
The vast majority of black bear mortality due to predation occurs among individuals less than two years old, specifically cubs and yearlings. These young bears are vulnerable due to their small size, limited defensive capabilities, and complete reliance on the sow for protection. For the first 16 to 18 months of life, the mother bear’s presence and vigilance serve as the most effective defense mechanism.
Cubs born during the winter denning period are safest, but vulnerability sharply increases when the family emerges in the spring. If separated from their mother, they are small enough to be easily overpowered by a wide variety of carnivores. Even under the sow’s protection, predators like coyotes, bobcats, and cougars have been documented preying on small cubs.
Studies suggest that approximately 60% of cubs successfully live past their first year, illustrating the high-risk period of their juvenile phase. An adult female black bear is highly protective, often chasing away larger animals, but she cannot be everywhere at once. The brief moments when a mother is distracted while foraging or traveling are often when an opportunistic predator can successfully isolate and attack a cub.
Major External Predators
A few larger carnivores pose a significant threat to black bears, specifically targeting sub-adults, injured individuals, or, in rare cases, healthy adults. The most formidable external threat is the Grizzly Bear (Ursus arctos), a larger and more aggressive species that dominates black bears where their ranges overlap. Grizzly bears actively kill black bears due to resource competition, particularly over concentrated food sources like salmon runs or large carcasses.
Fatal interactions frequently occur when a grizzly invades a black bear’s den during the winter, often targeting a sow and her cubs. The grizzly’s greater size and strength give it a decisive advantage in a direct conflict. Black bears often avoid confrontation by using their superior climbing ability, which is a primary anti-predator defense against grizzlies and other terrestrial threats.
Cougars, or mountain lions, are capable predators of black bears, though they typically only succeed against younger or smaller sub-adults. Their hunting strategy relies on a powerful ambush, which may bypass the black bear’s ability to defend itself. However, larger black bears often exhibit behavioral dominance over cougars, frequently displacing them from recent kills in a process known as kleptoparasitism.
Gray wolves, which hunt in coordinated packs, also pose a threat, particularly in areas where they are numerous. While a single wolf rarely attacks an adult black bear, a pack can overwhelm a bear, especially if the bear is surprised or focused on a food source. Wolves have been documented killing black bears, including instances of digging denning bears out of their winter shelters. Black bears are generally subordinate to wolf packs at a contested carcass, choosing to retreat rather than engage in a prolonged fight.
Intraspecific Mortality: Cannibalism
A significant source of mortality for black bears is intraspecific predation, or cannibalism, which primarily manifests as infanticide. This behavior is most often perpetrated by adult male bears, or boars, who kill cubs that are not their own. Infanticide can account for a large portion of cub deaths in some populations, sometimes reaching up to 50% of cub mortality.
The motivation behind this behavior is usually reproductive, known as sexually selected infanticide. By killing the dependent cubs, the male can hasten the female’s return to estrus, allowing him an opportunity to mate. While the primary goal is reproductive advantage, the subsequent consumption of the cub provides a nutritional benefit, making the event a form of cannibalism.
This intraspecific threat forces female black bears to be highly vigilant, often avoiding areas where large adult males are known to roam. Female bears will sometimes abort a pregnancy or abandon a den if they sense a significant threat from a large male. This internal pressure from conspecifics is a major factor shaping the survival and behavior of young black bears.