ANIMAL WORLD
Grizzly bear
(Ursus arctos)
Evolution:
The origins of Family Ursidae can be traced back to Cephalogale, a small, dog-like animal which lived in Europe during the early to mid-Tertiary. Cephalogale was the ancestor to Ursavus elmensis, the first bear-like carnivore. From this origin came the Ursidae family.
Members of Ursidae dispersed throughout the world. The spectacled bear diverged from other members of Ursidae approximately 12-13 million years ago, which is close to the time of divergence of the ancestral giant panda. The sloth bear lineage diverged later, approximately 7 million years ago.
Speciation and Isolation Mechanism:
There are many subspecies of brown bears (U. arctos sspp.) worldwide. However, the exact number and classification of subspecies is not widely agreed upon (Nowak 1991). Some early taxonomists have suggested that there are as many as 90 subspecies in North America and 271 subspecies of brown bears in Eurasia. However, many consider this to be a case of excessive over-splitting (Talbot & Shields 1996a). More recent findings indicate that there are two to nine subspecies of brown bears in Eurasia, and seven Eurasian subspecies (Nowak 1991, Rausch 1963, Waits et al. 1998).
Geographic Isolation- Polar bears are a relatively new species, and actually a subspecies, of Ursus arctos. Scientific evidence has found that the grizzly bears is a “precursor” to polar bears, which then went on to develop specializations for inhabiting the harsh Arctic. Proving their genetic compatibility, brown bears and polar bears can mate and produce viable, or fertile, offspring (Sterility).
Biogeography:
The brown bear is a very widespread species, originally native to much of the Northern Hemisphere . The brown bear once occupied most of Western North America, from the Great Plains to California and from Mexico to Alaska. In Eurasia, brown bears originally occurred from northern Africa, Spain, and Italy northward into Scandinavia and eastward through Asia to Japan.
Habitat:
Grizzly bears are specially adapted to survive the changing seasons. North America, grizzly bears are found in western Canada, Alaska, Wyoming, Montana, Idaho and a small population in Washington. Historically, they could be found from Alaska to Mexico and from California to Ohio.
Diet:
As omnivores, grizzlies will eat anything nutritious they can find, gorging on nuts, fruit, leaves, roots, fungi, insects, and a variety of animals including salmon and other fish, rodents, sheep, and elk. Their diet varies depending on what foods are available for the season.
Reproduction:
Grizzly bears are one of the slowest reproducing land mammals. Females do not typically reproduce until they are four or five years old. Grizzly bears mate between May and July, but the female’s body delays implantation of their eggs in the uterus until October or November. The mating season early may through mid-July. The cubs stay under their mother’s care for 2-3 years. While mother grizzlies are fiercely protective of their cubs.
Extition:
Grizzly bears have few enemies except other bears and humans, when they go wandering into camp grounds. Grizzlies are hunted primarily as game animals throughout Western Canada in spring and fall. They are illegally hunted by both the landowners seeing the bears as a threat to their livestock, and poachers interested in their hides, teeth, claws and internal organs for the Asian medical market. For many years across North America, there has been voiced concern about the illegal killing of grizzlies, but there is a growing world medical market for bear parts, especially gall bladders; some poachers even film the death of the bear to show that the gall bladders are real. In 1985, estimated populations of the grizzly were 1,200 in Alberta, 6,500 in British Columbia, and 4,000 to 5,000 in the Northwest Territories. Unfortunately, 95% of the grizzly bears who live past age 2 in North America die at the hands of humans from gunshot. People are the biggest threat to grizzlies not only because of hunters, but also because of the increasing human population and the resulting erosion of grizzly habitat.
Ecology:
The grizzly bear has several relationships with its ecosystem. One such relationship is a mutualistic relationship with fleshy-fruit bearing plants. After the grizzly consumes the fruit, the seeds are dispersed and excreted in a germinable condition. So, they are important predators and seed dispersers in the ecosystems in which they live. Today, there are an estimated 1,800 grizzly bears remaining in five populations in the lower 48 states. Behavior: Grizzly bears are normally solitary animals. However, they are not very territorial and they may be seen feeding together where food is abundant, such as at salmon streams. During warmer months, they eat a massive amount of food so they can live off body fat during the winter, when food is scarce. They may intake 40 kg (90 lbs.) of food each day, gaining over 1 kg (2.2 lbs.) of body weight a day. The grizzly bear usually forages for food in the early morning and evening and rests during the day.
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
