Courtship and copulation occur mid-May through early July; embryo implantation is delayed until fall. In delayed implantation the embryo develops slowly, while floating in the uterus. Eventually, it becomes attached to the wall of the uterus and development continues normally until birth.
Grizzly BearThe grizzly bear (Ursus arctos) is a large MAMMAL of the order CARNIVORA. The grizzly or brown bear differs from other North American carnivores in that, like other BEARS, it eats primarily PLANT matter. Grizzlies opportunistically kill or scavenge animals, especially ungulates, ground squirrels and insects. Coastal populations feed heavily on fish and shellfish. They are also attracted to edible garbage. In fall they dig dens and begin a 4-7 month dormant period during which they usually do not eat, urinate or defecate.
DescriptionGrizzlies have longer front claws and are larger than BLACK BEARS. Large males may weigh 250-400 kg; large females, 150-200 kg. Grizzlies have a hump on the back and a dish-shaped facial profile. They range from black through brown to blond. Often the ends of hair on the flanks, back and shoulders are grizzled (eg, have white or grey flecks).
Reproduction and Development
Courtship and copulation occur mid-May through early July; embryo implantation is delayed until fall. In delayed implantation the embryo develops slowly, while floating in the uterus. Eventually, it becomes attached to the wall of the uterus and development continues normally until birth. Young are born in January and February. Newborns weigh about 0.5 kg, are very immature, and are nursed inside dens for up to 3 months. Litters average 2 young (range 1-4). Females breed about once every 3 years (range 2-5 years). Grizzlies thus have few young and HUNTING must be carefully regulated to maintain a population. In the wild most die before reaching adulthood; 15-25 years is considered old.
Mothers may defend their young and males may fight, especially during breeding season. Occasionally, aggression is directed toward humans: in Canada's NATIONAL PARKS, about 1 visitor in 2 million is injured by a grizzly. Grizzlies may stand on their hind legs when sensing their environment. They typically charge on 4 legs and can run at least 50 km/h.