Subspecies of brown bear

Formerly or currently considered subspecies or populations of brown bears have been listed as follows:

Ecotypes or regional populations
Brown bear size, most often measured in body mass, is highly variable and is correlated to extent of food access. Therefore, bears whose range in areas with access to openings, cover, and moisture or water are on average larger, whereas those bears that range into enclosed forested areas or arid, sparsely vegetated regions, both of which tend to be suboptimal foraging habitat for brown bears, average smaller. The brown bear in northern Europe (i.e., Scandinavia, eastern Europe, western Russia), Yellowstone National Park or interior Alaska seasonally weigh on average between 115 and 360 kg, from mean low adult female weights in spring to male bear mean high weights in fall. Brown bears from the Yukon Delta, interior British Columbia, Jasper National Park and southern Europe (i.e., Spain, the Balkans) can weigh from 55 to 175 kg on average. These mass variations represent only two widespread subspecies, the grizzly bear in North America and the Eurasian brown bear in Europe. Due to the lack of genetic variation within subspecies, the environmental conditions in a given area likely plays the largest part in such weight variations.

The grizzly is especially variable in size, as grizzlies from the largest populations, i.e., interior Alaska, with the heaviest weights recorded in Nelchina, Alaska, nearly three times heavier in males than the smallest grizzlies from Alberta, Canada's Jasper National Park. Between the sexes, the grizzlies of Nelchina average around 207 kg, whereas the Jasper grizzlies averaged about 74 kg. The enclosed taiga habitat of Jasper presumably is sub-optimal foraging habitat for grizzlies, requiring them to range widely and feed sparsely, thus reducing body weights and putting bears at risk of starvation, while in surfaces areas in the tundra and prairie are apparently ideal for feeding. Even elsewhere in Alberta, weights averaging more than twice those of Jasper grizzlies have been recorded. A gradual diminishment in body size is noted in grizzly bears from the sub-Arctic zone, from the Brooks Range to the Mackenzie Mountains, presumably because food becomes much sparser in such regions, although perhaps the most northerly recorded grizzly bears ever, in the Northwest Territories, was a large and healthy male weighing 320 kg, more than twice as much as an average male weighs near the Arctic Circle. Data from Eurasia similarly indicates a diminished body mass in sub-Arctic brown bears, based on the weights of bears from northern Finland and Yakutia.

Head-and-body length in grizzly bears averages from 1.8 to 2.13 m while in Eurasian brown bears it similarly averages from 1.7 to 2.1 m. Adult shoulder height averaged 95.2 cm in Yellowstone (for any bear measured five or more years old) and a median of 98.5 cm (for adults only 10 or more years old) in Slovakia. Standing on its hindlegs, a posture only assumed occasionally, typically-sized brown bears can reportedly range from 1.83 to 2.75 m in standing height. Exceptionally large inland specimens have been reported in several parts of North America, Europe, Russia and even Hokkaido. The largest recorded grizzlies from Yellowstone and Washington both weighed approximately 500 kg and Eastern European bears have been weighed in Slovakia and Bulgaria of up to 400 kg, about double the average weight for male bears in these regions. Among the grizzly and Eurasian brown bear subspecies, the largest reportedly shot from each being 680 kg and 481 kg, respectively. The latter bear, from Western Russia, reportedly measured just under 2.5 m in head-and-body length.

In Eurasia, the size of bears roughly increases from the west to the east, with the largest bears there native to Eastern Russia. Even in the nominate subspecies, size increases in the eastern limits, with mature male bears in Arkhangelsk Oblast and Bashkortostan commonly exceeding 300 kg. Other bears of intermediate size may occur in inland populations of Russia. Much like the grizzly bear and Eurasian brown bear, populations of the Ussuri brown bear (U. a. lasiotus) and the East Siberian brown bear (U. a. collaris) may vary widely in size. In some cases, the big adult males of these populations may have matched the Kodiak bear in size. East Siberian brown bears from outside the sub-Arctic and mainland Ussuri brown bears average about the same size as the largest-bodied populations of grizzly bears, i.e., those of similar latitude in Alaska, and have been credited with weights ranging from 100 to 400 kg throughout the seasons. On the other hand, the Ussuri brown bears found in the insular population of Hokkaido are usually quite small, usually weighing less than 150 kg, exactly half the weight reported for male Ussuri brown bears from Khabarovsk Krai. This is due presumably to the enclosed mixed forest habitat of Hokkaido. A similarly diminished size has been reported in East Siberian brown bears from Yakutia, as even adult males average around 145 kg, thus about 40% less than the average weight of male bears of this subtype from central Siberia and the Chukchi Peninsula.

In linear measurements and mean body mass, several subspecies may vie for the title of smallest subtype, although thus far, their reported body masses broadly overlaps with those of the smaller-bodied populations of Eurasian brown bears and grizzly bears. Leopold (1959) described the now-extinct Mexican grizzly bear (U. a. nelsoni) that, according to Rausch (1963), as the smallest subtype of grizzly bear in North America, although the exact parameters of its body size are not known today. Bears of the Syrian subspecies (U. a. syriacus) will reportedly weigh around 100 to 160 kg in adulthood. The Himalayan brown bear (U. a. isabellinus) is another rival for the smallest subspecies; in Pakistan, this subtype averages about 70 kg in females and 135 kg in males. Himalayan brown bear females were cited with an average head-and-body length of merely 1.4 m. Brown bears of the compact Gobi Desert population, which is not usually listed as a distinct subspecies in recent decades, weigh around 90 to 138 kg between the sexes, so they are similar in weight to bears from the Himalayas and even heavier than grizzlies from Jasper National Park. However, the Gobi bear has been reported to measure as small as 1 m in head-and-body length, which, if accurate, would make them the smallest known brown bear in linear dimensions. These smallest brown bear subtypes are characteristically found in "barren-ground" type habitats, i.e., sub-desert in bears of the Syrian subspecies and the Gobi subtype and arid alpine meadow in Himalayan brown bears. The largest subspecies are the Kodiak bear (U. a. middendorffi) and the questionably-distinct peninsular giant bear or coastal brown bear (U. a. gyas). Also, the extinct California grizzly bear (U. a. californicus) was rather large. Once mature, the typical female Kodiak bear can range in body mass from 120 to 318 kg and from sexual maturity onward, males range from 168 to 675 kg. According to the Guinness Book of World Records the average male Kodiak bear is 2.44 m in total length (head-to-tail) and has a shoulder height of 1.33 m. When averaged between their spring low and fall high weights from both localities, males from Kodiak island and coastal Alaska weighed from 312 to 389 kg with a mean body mass of 357 kg while the same figures in females were 202 to 256 kg with a mean body mass of 224 kg. By the time they reach or exceed eight to nine years of age, male Kodiak bears tend to be much larger than newly mature six-year-old males, potentially tripling their average weight within three years' time, and can expect to average between 360 and 545 kg. The reported mean adult body masses for both sexes of the polar bear are very similar to the peninsular giant and Kodiak bears. Due to their roughly corresponding body sizes, the two subtypes and the species can both legitimately be considered the largest living member of the bear family Ursidae and the largest extant terrestrial carnivores. The largest widely accepted size for a wild Kodiak bear, as well as for a brown bear, was for a bear killed in English Bay on Kodiak Island in fall 1894 as several measurements were made of this bear, including a body mass of 751 kg, and a hind foot and a voucher skull were examined and verified by the Guinness Book of World Records. Claims have been made of larger brown bears, but these appear to be poorly documented and unverified and some, even if recited by reputable authors, may be dubious hunters' claims. The largest variety of brown bear from Eurasia is the Kamchatkan brown bear (U. a. beringianus). In the Kamchatkan brown bears from past decades, old males have been known to reach a body mass of 500 - 685 kg by fall, putting the subtype well within Kodiak bear sizes and leading it to be considered the largest of the extant Russian subtypes. However, a diminishment in body size of U. a. berigianus has been noted, mostly likely in correlation with overhunting. In the 1960s and 1970s, most adult Kamchatkan brown bears weighed merely between 150 and 285 kg; however, mean weights of mature male bears have been reported as averaging 350 to 450 kg in 2005.