The Grizzly Bear, sometimes called the Silvertip Bear, has traditionally been treated as a subspecies Ursus arctos horribilis of the Brown Bear, living in North America. more...
However, DNA analysis has recently revealed that the subspecies of brown bears, both Eurasian and North American, are genetically quite homogeneous, and that their genetic phylogeography does not correspond to their traditional taxonomy. Therefore, the common name grizzly bear can be appropriately used to refer to interior North American Brown Bears, whereas the coastal bears of North America are referred to as Kodiak Bears or Kodiak Brown Bears, and those of Europe, the European Brown Bear.
Grizzly Bears reach weights of 180-680 kg (400-1500 lbs); the male is on average 1.8 times as heavy as the female, an example of sexual dimorphism. Their coloring ranges widely across geographic areas, from blond to deep brown or black. These differences, once attributed to subspeciation, are now thought to be primarily due to the different environments these bears inhabit, particularly with regard to diet and temperature.
The grizzly has a large hump over the shoulders which is a muscle mass used to power the forelimbs in digging. The head is large and round with a concave facial profile. In spite of their massive size, these bears can run at speeds of up to 55 km/h (35 mph).
Normally a solitary, nocturnally active animal, in coastal areas the grizzly congregates alongside streams and rivers during the salmon spawn. Every other year females (sows) produce 1-4 young (most commonly 2) which are small and weigh only about 500 g (1 pound). Sows are very protective of their offspring.
Being omnivores, grizzlies feed on a variety of plants and berries including roots or sprouts and fungi, as well as fish, insects and small mammals. The larger bears have been known to predate large mammals such as moose, sheep and caribou. Bears with access to a protein-rich diet, such as the coastal bears which feed on salmon, can grow much larger than their herbivorous cousins.
In preparation for winter, bears will gain hundreds of kilogrammes of fat before going into a state of false hibernation. There is some debate amongst professionals as to whether or not grizzly bears technically hibernate. Much of this debate revolves around body temperature and the ability for the bears to move around during hibernation on occasion. One interesting adaptation is that Grizzly Bears have the ability to partially recycle their body wastes during this period. In some areas where food is plentiful all year round, Grizzly Bears will forgo hibernation altogether.
The Grizzly Bear is listed as threatened in the contiguous United States, and endangered in parts of Canada. It is currently slowly repopulating areas where it was previously extirpated.
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