Brown Bear

The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from 300 to 780 kilograms (660 to 1,700 lb) and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator. There are several recognized subspecies within the brown bear species. In North America, two types are generally recognized, the coastal brown bear and the inland grizzly, and the two types could broadly define all brown bear subspecies. Grizzlies weigh as little as 350 lb (159 kg) in Yukon, while a brown bear, living on a steady, nutritious diet of spawning salmon, from coastal Alaska and Russia can weigh 1,500 lb (682 kg). The exact number of overall brown subspecies remains in debate.
Brown bears often use their large size for intimidation when a kill or a territory is in dispute with another large predator and they are normally dominant in such interactions. Sometimes, the conflict will escalate to the point of violence, but usually threat displays are sufficient, since most animals try to avoid potential bodily harm. However, the massive strength and size of the brown bear will usually result in it winning violent conflicts, even against wolf packs and Siberian Tigers. In situations where the interspecies conflict turns deadly, brown bears may also eat the competitor, despite it not being the primary reason for attack.
Brown bears regularly intimidate wolves away from their kills. In Yellowstone National Park, brown bears pirate wolf kills so often, Yellowstone's Wolf Project Director Doug Smith wrote, "It's not a matter of if the bears will come calling after a kill, but when." Though conflict over carcasses is common, on rare occasions the two predators tolerate each other on the same kill. Given the opportunity, both species prey on the other's cubs. Conclusively, the individual power of the bear against the collective strength of the wolf pack usually results in a long battle for kills or domination. In some areas, the brown bear also regularly displaces cougars from their kills.
Adult bears are generally immune from predatory attacks from anything other than other bears. Some bears emerging from hibernation seek tigers to steal their kills. Indeed, Russian researchers have identified "satellite bears" who "follow tigers over extensive periods of time, sequentially usurping kills"; these bears were observed tracking tigers in spring snow and regularly usurped their kills. In the Russian Far East, brown bears along with smaller Asiatic black bears constitute 5–8% of the diet of Siberian tigers. In particular, the brown bear's input is estimated to be 1.0–1.5% in one source. However, another source states that such attacks are rare and do not have any actual significance because Siberian tigers are almost extinct. Siberian tigers most typically attack brown bears in the winter or in the late autumn and early spring, and when ungulate populations decrease. Adult bears, generally smaller ones, are sometimes vulnerable to tiger attacks and have been killed in their dens in winter, with the tiger taking advantage of the bear's hibernating condition. There are also records of bears killing tigers, including fully grown adult males and tigers whose sex and age were not specified, either in self-defense, or in disputes over kills or for consumption.
Brown bears usually dominate other bear species in areas where they coexist. Due to their smaller size, American black bears are at a competitive disadvantage to brown bears in open, unforested areas. Although displacement of black bears by brown bears has been documented, actual interspecific killing of black bears by brown bears has only occasionally been reported. Confrontation is mostly avoided due to the black bear's diurnal habits and preference for heavily forested areas, as opposed to the brown bear's largely nocturnal habits and preference for open spaces. Brown bears may attack Asian black bears. They will eat the fruit dropped by the latter species from trees, as they themselves are too large and cumbersome to climb.
There has been a recent increase in interactions between brown bears and polar bears, theorized to be caused by climate change. Brown bears have been seen moving increasingly northward into territories formerly claimed by polar bears. Brown bears tend to dominate polar bears in disputes over carcasses, and dead polar bear cubs have been found in brown bear dens.