Ursus arctos horribilis
Oso plateado, Oso grizzly (Sp), Grizzlybär (G), Ours grizzly (F). "Grizzly" is derived from the grizzled appearance of the white-tipped guard hairs in many individuals.
DESCRIPTION (male) Head and body length 6-8 feet (1.8 to 2.4 m). Tail length 3-4 inches (7.6 to 10.2 cm). Shoulder height 3-4 feet (0.9 to 1.2 m). Weight as much as 500-750 pounds (225-340 kg). Females are much smaller. Chromosome count is 74.
The grizzly is a powerfully built bear with long, thick hair that varies in color from dark brown to pale yellowish-brown. (The so-called Toklat grizzly from the Alaska Range is a striking pale golden color with chocolate-colored lower parts.) The body is massive and thick, with a prominent hump on the shoulders and a huge head supported by a short, muscular neck. The facial profile is concave. The front claws often exceed 3-3/4 inches (95 cm) in length, and are used primarily for digging and as weapons.
BEHAVIOR Except when mating, or in the case of a mother with cubs, grizzlies are solitary and unsociable. Males, especially, are great wanderers. Grizzlies mate from late May till the end of June. The female breeds every 2-3 years, with 1-4 cubs, but generally two, born in the den during January or February. She is a good mother and keeps the cubs with her for two years, or often longer. Full grown at 8-10 years, with a life expectancy of 25-30 years.
Except for polar bears, grizzlies are the most carnivorous of bears. They kill animals as large as moose and elk, dig rodents from their burrows, and eat spawning fish and carrion. Nonetheless, the grizzly cannot obtain enough meat to sustain itself, and must rely on vegetable matter for much of its intake, eating grasses, sedges, roots, tubers, buds, berries and nuts. It dens in the fall and sleeps until April; however, if its sleep is disturbed, it can come to life quickly. Senses of smell and hearing are excellent, eyesight not as good, but able to make out moving objects at a considerable distance. Surprisingly agile, it can run 30 mph (48 km/h) on the flat, and can gallop for miles over steep mountain slopes. An excellent swimmer, it crosses large rivers and lakes that are many miles in width. Cubs can climb trees, but mature bears cannot because their claws are too long and their bodies too heavy.
HABITAT Adaptable to a wide range of terrain and climate, including tundra, forests, mountains, and semi-deserts.
DISTRIBUTION In pioneer times, grizzly bears were common in most of western North America from Alaska to northern Mexico, and from the western coastal mountains eastward to the Great Plains. The largest remaining populations today are in Alaska and Canada. Grizzlies are found in all parts of Alaska except for the range of the Alaska brown bear (Game Management Units 1-10 and 14-18). In Canada, they are found mainly in British Columbia and the Yukon, but also in western Alberta and southwestern Northwest Territories, particularly in the Mackenzie Mountains. (The common grizzly gives way to the barren-ground grizzly east of the Mackenzie River Delta and north of the tree line in the Northwest Territories and Nunavut.) There are a few isolated populations in the 48 conterminous United States, especially in Montana, Wyoming and Idaho, plus Yellowstone and Glacier national parks. Survivors may still exist in a remote area of Mexico's Sierra Madre Occidental.
REMARKS The grizzly is one of the finest hunting trophies on the North American continent. (Theodore Roosevelt considered it the top trophy.) For a big bear with a big skull, one should search the salmon rivers of British Columbia or of Alaska north of Unit 18. Interior or mountain grizzlies run smaller than the coastal salmon-eaters because they have less to eat. (Observing a grizzly eating berries on a mountainside, one wonders how the nourishment obtained can possibly compensate for the energy expended.) Interior grizzlies make up for their lack of size by having a beautiful coat of long, thick hair that comes in a variety of colors. A highly satisfactory way of hunting grizzlies is the classic fall horseback hunt for several species. Here, the sheep rifle is generally used for the bear as well; while a bit light, it will suffice with good bullets and good shooting. A grizzly is smaller than an Alaska brown bear, but just as tough and probably more dangerous.
TAXONOMIC NOTES Classification of grizzly bears in North America needs updating. The most recent lists 60 or so species and/or subspecies within the SCI boundaries for grizzly bear, which is far too many. All except those we have consigned to the barren-ground grizzly are combined here, with horribilis Ord, 1815 having priority.
STATUS The grizzly can survive only in wilderness, because it coexists poorly with man. Considered dangerous to humans, and with a history of feeding on livestock, it has been exterminated over large areas.
The Mexican grizzly (subspecies nelsoni), formerly of northern Mexico and southwestern New Mexico, but now probably extinct, was listed as endangered by the USF&WS (1970) and the IUCN, and is on Appendix I of CITES (1975).