The grizzly bear is a large, powerful North American omnivore that occupies a high position in its ecological niche across its range in western Canada and the United States. For a healthy, mature grizzly, true natural predation is extremely rare. The threats that lead to mortality are almost entirely focused on young bears or result from interactions with humans.
The Apex Predator Status
The adult grizzly bear maintains its position at the top of the food chain due to its physical attributes and assertive behavior. A large male grizzly can weigh between 400 to over 600 pounds, an immense size that deters confrontation. This mass is supported by a muscular hump above the shoulders, which provides the power needed for digging and delivering powerful forelimb strikes.
A grizzly’s defense includes non-retractable claws up to four inches long and a bite force estimated at 1,000 pounds per square inch. Despite their bulk, grizzlies are surprisingly fast, capable of short sprints up to 35 miles per hour. These traits make preying upon a healthy adult highly dangerous for other large carnivores.
Wildlife Threats Targeting Cubs and Subadults
Predation within the grizzly population itself is the most significant non-human threat to young bears. Adult male grizzlies frequently engage in infanticide, killing cubs to bring the sow back into estrus. This sexually selective behavior allows the male to mate with the female earlier, as raising a litter can take up to three years.
Cubs and subadults are the only age classes vulnerable to other large predators, though such attacks are uncommon. Coordinated packs of gray wolves or a cougar may occasionally attempt to prey on an isolated cub. However, the sow fiercely defends her offspring, meaning these conflicts are usually avoided by other predators. The high mortality rate for young grizzlies is often attributed to natural causes, including disease, starvation, and these rare acts of predation.
Mortality Caused by Human Interaction
Since natural predation on adult grizzlies is negligible, human activity is the dominant factor controlling their survival rates. Studies show that between 71 and 90 percent of independent adult grizzly bear deaths across their range are caused by humans.
These deaths include regulated hunting and defense-of-life kills, where a bear is destroyed following a perceived threat to human safety or property. Habitat fragmentation forces bears to cross human infrastructure, leading to frequent fatalities from vehicular and train collisions. Management removal and poaching also contribute to this high rate, making human interaction the primary influence on grizzly population dynamics.