Adult grizzly bears have no regular natural predators. They sit at the top of the food chain in every North American ecosystem they inhabit, classified as apex predators by wildlife agencies and ecologists alike. That said, grizzly bears are not completely invulnerable. Cubs face significant threats, adult males kill other bears, and in one corner of the world, a big cat occasionally takes down a brown bear.
Why Adults Have No Natural Predators
A full-grown grizzly is simply too large and too dangerous for other animals to hunt. Males typically weigh 400 to 700 pounds, with some coastal populations exceeding 1,000 pounds. Their claws can reach four inches long, and their bite force measures around 1,160 psi, enough to crush a bowling ball. No predator in North America can reliably take down an animal with that combination of size, strength, and aggression.
Wolves share habitat with grizzlies across much of their range, and the two species regularly compete over kills. Wolf packs will harass a grizzly to drive it off a carcass, and grizzlies will steal wolf kills. But wolves do not hunt adult grizzly bears. The risk of injury is too high and the odds of success too low for wolves to treat grizzlies as prey.
The Biggest Threat: Other Grizzly Bears
The most dangerous predator a grizzly bear faces is another grizzly. Adult males are documented killing cubs, juveniles, adult females, and occasionally other males. This behavior, called intraspecific predation, is well studied and plays a significant role in grizzly population dynamics.
Infanticide is the most common form. Males kill unrelated cubs because it brings the mother back into breeding condition sooner, giving the infanticidal male a chance to sire his own offspring. Female grizzlies are well aware of this risk. Research on denning behavior shows that mothers choose den sites at higher elevations and on steeper slopes than males, specifically to put distance between their cubs and dangerous males. Juvenile bears also avoid areas frequented by dominant adult males, segregating themselves in space and time to reduce their chances of a fatal encounter.
This threat shapes grizzly bear society in fundamental ways. It influences where females feed, where they den, and how they move through the landscape, all organized around avoiding large males.
Cub Survival Is Remarkably Low
Grizzly cubs are vulnerable in a way adults are not. In Denali National Park, only about 35% of cubs survive their first year. Out of 148 cubs tracked in one long-term study, 99 died. Yearling survival was better but still harsh, with roughly 40% of yearlings dying before reaching age two. Two-thirds of cub deaths occurred before July, during the period when cubs are smallest and most defenseless.
In 54% of monitored litters, mothers lost every single cub. These numbers are consistent across non-hunted populations: Katmai National Park in Alaska recorded 34% cub survival, while Yellowstone came in at 49%. Researchers believe most of these deaths result from starvation or predation, though the exact cause is usually impossible to confirm because cubs are so small that little evidence remains.
The predation that does occur likely comes primarily from adult male grizzlies, though wolves and other bears could also be responsible in some cases. The key point is that while adult grizzlies are nearly untouchable, their offspring face intense mortality pressure from multiple sources.
The One Exception: Siberian Tigers
In the Russian Far East, the Amur tiger is the only animal on Earth that regularly preys on brown bears (the same species as the grizzly, just a different population). Research conducted in the Sikhote-Alin Nature Reserve between 1992 and 2013 found that bears made up 2.2% of all confirmed tiger kills, and bear remains appeared in 8.4% of tiger scat samples. Brown bears specifically can account for up to 5% of a tiger’s diet.
These encounters are not one-sided, though. Among 45 documented aggressive encounters between tigers and brown bears, the bear died 51% of the time, the tiger died 27% of the time, and both animals survived in 22% of cases. Most brown bears killed by tigers are young animals or females, and the kills are typically made by male tigers. Adult male brown bears are rarely targeted, likely because they are large enough to seriously injure or kill the tiger.
This dynamic does not apply to North American grizzlies, which share no habitat with tigers. But it is the clearest example in nature of a predator that can and does hunt brown bears with some regularity.
Humans Are the Primary Cause of Death
In practical terms, humans are the closest thing adult grizzly bears have to a predator. Data from the Selkirk Mountains recovery area shows that over a 44-year period from 1980 to 2024, 79 out of 95 known grizzly bear deaths were human-caused. Only 12 were attributed to natural causes. Recent data from 2019 to 2024 puts human-caused mortality at an average of 3.9% of the population per year, roughly two bears annually in that area.
The causes break down into several categories: management removals (bears killed by wildlife agencies after conflicts), vehicle and train collisions, poaching, mistaken identity during other hunting seasons, and self-defense killings. In the Selkirk data, management removals and vehicle collisions were the most common. Males were killed at three times the rate of females, likely because males range more widely and encounter human infrastructure more often.
Prehistoric Predators That No Longer Exist
The story was different thousands of years ago. When grizzly bear ancestors first colonized North America, they shared the landscape with predators that could have posed a genuine threat. The giant short-faced bear was larger than any modern brown bear and built for speed on the open grasslands. American lions, saber-toothed cats, and dire wolves also roamed the continent. In that predator-rich environment, early brown bears were not automatically dominant.
All of those competitors went extinct by the end of the last ice age, roughly 11,000 years ago. With their disappearance, the brown bear inherited the role of North America’s top land predator, a position it has held unchallenged by any other animal species ever since.