One way to identify a brown bear is by the hump at the top of its shoulder. The hump, which is made of muscle, is believed to make it easier for the bear to dig a den. No other extant species of bear has this hump. Adult bears have short tails and sharp teeth with curved lower canines. Their skulls are heavy and concave. The brown bear’s range includes northern North America and Eurasia, including the United States, Canada, Russia, China, Central Asia, Scandinavia, Romania, Caucasus, and Anatolia. At one time, it was also found throughout Europe, in northern Africa, and as far south as Mexico in North America. Brown bears’ claws are large, curved, and blunt. Their claws are straighter and longer than those of black bears. Unlike the black bear, which readily climbs trees, the brown bear climbs less frequently due to its weight and claw structure. Brown bear size is highly variable, depending both on subspecies and food availability. Males are about 30% larger than females. An average-sized bear might range from 5 to 8 feet in length and weigh 700 pounds, however, much smaller and much larger specimens occur. On average, polar bears are larger than brown bears, but a large grizzly and a polar bear are comparable. You might guess from their name that brown bears are brown. However, these bears can be brown, red, tan, cream, bicolored, or nearly black. Sometimes the tips of their fur are colored. Fur length varies according to the season. In the summer, their fur is shorter. In the winter, some brown bears’ fur can reach 4 to 5 inches in length. Brown bears inhabit a wide range of environments. They have been recorded living at altitudes ranging from sea level to 5000 m (16000 ft). They inhabit temperature forests, preferring semi-open regions, but also live on the tundra, prairies, and estuaries. Bears that live near people may prey on pets and livestock and scavenge for human food. Brown bears eat up to 90 pounds of food per day in autumn and weigh twice as much as when they emerge from their dens in the spring. Adult brown bears face few predators. Depending where they live, they may be attacked by tigers or other bears. Brown bears dominate gray wolves, cougars, black bears, and even polar bears. Large herbivores rarely threaten the bears, but may fatally wound one in self-defense or protecting calves. Although brown bears have a reputation as fierce carnivores, they actually obtain as much as 90% of their calories from vegetation. Bears are omnivorous and naturally curious about eating nearly any creature. Their preferred food is anything abundant and easy to obtain, which varies according to the season. Their diet includes grass, berries, roots, carrion, meat, fish, insects, nuts, flowers, fungi, moss, and even pine cones.