Ursidae is a family of mammals in the order Carnivora, which includes the giant panda, brown bear, and polar bear, and many other extant or extinct mammals. A member of this family is called a bear or an ursid. They are widespread across the Americas and Eurasia. Bear habitats are generally forests, though some species can be found in grassland and savana regions, and the polar bear lives in arctic and aquatic habitats. Most bears are 1.2–2 m (4–7 ft) long, plus a 3–20 cm (1–8 in) tail, though the polar bear is 2.2–2.44 m (7–8 ft) long, and some subspecies of brown bear can be up to 2.8 m (9 ft). Weights range greatly from the sun bear, which can be as low as 35 kg (77 lb), to the polar bear, which can be as high as 726 kg (1,600 lb). Population sizes vary, with six species classified as vulnerable with populations as low as 500, while the brown bear has a population of over 100,000 and the American black bear around 800,000. Many bear species primarily eat specific foods, such as seals for the polar bear or termites and fruit for the sloth bear, but with the exception of the giant panda, which exclusively eats bamboo, ursids are omnivorous when necessary. No ursid species have been domesticated, though some bears have been trained for entertainment.[1]
The eight species of Ursidae are split into five genera in three subfamilies: the monotypic Ailuropodinae, the panda bears; Tremarctinae, the short-faced bears; and Ursinae, containing all other extant bears. Extinct species have also been placed into all three extant subfamilies, as well as three extinct ones: Agriotheriinae, Hemicyoninae, and Ursavinae. Over 100 extinct Ursidae species have been found, though due to ongoing research and discoveries the exact number and categorization is not fixed.