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Brown Bear

Ursus arctos

Description 12

Brown bears are often not fully brown. They have long, thick fur, with a moderately long mane at the back of the neck which varies somewhat across the types. In India, brown bears can be reddish with silver tips, while in China, brown bears are bicolored with a yellow-brown or whitish cape across the neck, chest, and shoulders. North American grizzlies can be dark brown (almost black) to cream (almost white) or yellowish brown and often have darker colored legs. The common name grizzly stems from their typical coloration, with the hairs on their back usually being brownish-black at the base and whitish-cream at the tips, giving them their distinctive "grizzled" color. The winter fur is very thick and long, especially in northern subspecies, and can reach 11 to 12 centimetres (4 to 5 in) at the withers. The winter hairs are thin, yet rough to the touch. The summer fur is much shorter and sparser, and its length and density varies geographically.

Brown bears have very large and curved claws, those present on the forelimbs being longer than those on the hind limbs. They may reach 5 to 6 centimetres (2.0 to 2.4 in) and may measure 7 to 10 centimetres (2.8 to 3.9 in) along the curve. They are generally dark with a light tip, with some forms having completely light claws. Brown bear claws are longer and straighter than those of American black bears (Ursus americanus). The claws are blunt, while those of a black bear are sharp. Due to their claw structure, in addition to their excessive weight, adult brown bears cannot typically climb trees as can both species of black bear, although in rare cases adult female brown bears have been seen in trees. The claws of a polar bear are also quite different, being notably shorter but broader with a strong curve and sharper point, presumably both as an aid to traveling over ice (sometimes nearly vertically) and procuring active prey. The paws of the brown bear are quite large. The rear feet of adult bears have been found to typically measure 21 to 36 cm (8.3 to 14.2 in) long, while the forefeet tend to measure about 40% less in length. All four feet in average sized brown bears tend to be about 17.5 to 20 cm (6.9 to 7.9 in) in width. In large coastal or Kodiak bear males, the hindfoot may measure up to 40 cm (16 in) in length, 28.5 cm (11.2 in) in width, while outsized Kodiak bears having had confirmed measurements of up to 46 cm (18 in) along their rear foot. Brown bears are the only extant bears with a hump at the top of their shoulder, which are made entirely of muscle, this feature having developed presumably for imparting more force in digging, which is habitual during foraging for most bears of the species and also used heavily in den construction prior to hibernation.

Adults have massive, heavily built concave skulls, which are large in proportion to the body. The forehead is high and rises steeply. The projections of the skull are well developed when compared to those of Asian black bears (Ursus thibetanus): the latter have sagittal crests not exceeding more than 19–20% of the total length of the skull, while the former have sagittal crests comprising up to 40–41% of the skull's length. Skull projections are more weakly developed in females than in males. The braincase is relatively small and elongated. There is a great deal of geographical variation in the skull, and presents itself chiefly in dimensions. Grizzlies, for example, tend to have flatter profiles than European and coastal American brown bears. Skull lengths of Russian bears tend to be 31.5 to 45.5 centimetres (12.4 to 17.9 in) for males, and 27.5 to 39.7 centimetres (10.8 to 15.6 in) for females. The width of the zygomatic arches in males is 17.5 to 27.7 centimetres (6.9 to 11 in), and 14.7 to 24.7 centimetres (5.8 to 9.7 in) in females. Brown bears have very strong teeth: the incisors are relatively big and the canine teeth are large, the lower ones being strongly curved. The first three molars of the upper jaw are underdeveloped and single crowned with one root. The second upper molar is smaller than the others, and is usually absent in adults. It is usually lost at an early age, leaving no trace of the alveolus in the jaw. The first three molars of the lower jaw are very weak, and are often lost at an early age. The teeth of brown bears reflect their dietary plasticity and are broadly similar to other bears excluding the two most herbivorous living bears, the giant panda (Ailuropoda melanoleuca) and spectacled bear (Tremarctos ornatus), which have blunt, small premolars (ideal for grinding down fibrous plants) compared to the jagged premolars of ursid bears that at least seasonally often rely on flesh as a food source. The teeth are reliably larger than American black bears but average smaller in molar length than polar bears. Brown bears have the broadest skull of any extant ursine bear, only the afforementioned most herbivorous living bears exceed them in relative breadth of the skull. Another extant ursine bear, the sloth bear (Melursus ursinus), has a proportionately longer skull than the brown bear and can match the skull length of even large brown bear subtypes, presumably as an aid for foraging heavily on insect colonies for which a long muzzle is helpful as an evolved feature in several unrelated mammalian groups.

The size of brown bears is the most variable of modern bears. The typical size depends upon which population it is from, and most accepted subtypes vary widely in size. This is in part due to sexual dimorphism, as male brown bears average at least 30% larger in most subtypes. Individual bears also vary in size seasonally, weighing the least in spring due to lack of foraging during hibernation, and the most in late fall, after a period of hyperphagia to put on additional weight to prepare for hibernation. Therefore, a bear may need to be weighed in both spring and fall to get an idea of its mean annual weight.

The normal range of physical dimensions for a brown bear is a head-and-body length of 1.4 to 2.8 m (4 ft 7 in to 9 ft 2 in) and a shoulder height of 70 to 153 cm (2 ft 4 in to 5 ft 0 in). The tail is relatively short, as in all bears, ranging from 6 to 22 cm (2.4 to 8.7 in) in length. The smallest brown bears, females during spring among barren-ground populations, can weigh so little as to roughly match the body mass of males of the smallest living bear species, the sun bear (Helarctos malayanus), while the largest coastal populations attain sizes broadly similar to those of the largest living bear species, the polar bear. Interior brown bears are generally smaller than is often perceived, being around the same weight as an average Southern African lion, at an estimate average of 180 kg (400 lb) in males and 135 kg (298 lb) in females, whereas adults of the coastal populations weigh about twice as much. The average weight of adult male bears from 19 populations, from around the world and various subspecies (including both large and small bodied subspecies), was found to 217 kg (478 lb) while adult females from 24 populations were found to average 152 kg (335 lb).

Brown bear size, most often measured in body mass, is highly variable and is correlated to extent of food access. Therefore, bears who range in ecozones that include have access to openings, cover and moisture or water tend to average larger whereas those bears that range into ecozones with enclosed forested areas or arid, sparsely vegetated regions, both of which tend to be sub-optimal 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 (254 and 794 lb), from mean low adult female weights in spring to male bear mean high weights in fall. 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 (121 to 386 lb) 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 (456 lb), whereas the Jasper grizzlies averaged about 74 kg (163 lb). 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 the Alberta province, 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 (710 lb), 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 (5 ft 11 in to 7 ft 0 in) while in Eurasian brown bears it similarly averages from 1.7 to 2.1 m (5 ft 7 in to 6 ft 11 in). Adult shoulder height averaged 95.2 cm (3 ft 1 in) in Yellowstone (for any bear measured five or more years old) and a median of 98.5 cm (3 ft 3 in) (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 (6 ft 0 in to 9 ft 0 in) 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 state both weighed approximately 500 kg (1,100 lb) and eastern European bears have been weighed in Slovakia and Bulgaria of up to 400 kg (880 lb), 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 (1,500 lb) and 481 kg (1,060 lb), respectively. The latter bear, from western Russia, reportedly measured just under 2.5 m (8 ft 2 in) 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 (660 lb). Other bears of intermediate size may occur in inland populations of Russia. Much like the grizzly 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 bear, i.e. those of similar latitude in Alaska, and have been credited with weights ranging from 100 to 400 kg (220 to 880 lb) 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 (330 lb), 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 (320 lb), 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 and grizzly bears. Leopold (1959) described the now extinct Mexican grizzly bear 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 from the Syrian (U. a. syriacus) subspecies will reportedly weigh around 100 to 160 kg (220 to 350 lb) in adulthood. The Himalayan brown bear (U. a. isabellinus) is another rival for smallest subspecies, in Pakistan this subtype averages about 70 kg (150 lb) in females and 135 kg (298 lb) in males. Himalayan brown bear females were cited with an average head-and-body length of merely 1.4 m (4 ft 7 in). 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 (198 to 304 lb) between the sexes, so 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 (3 ft 3 in) 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 from the Syrian and Gobi subtype and arid alpine meadow in Himalayan bears.

The largest subspecies are the Kodiak bear (U. a. middendorffi) and the questionably distinct peninsular 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 (265 to 701 lb) and while from sexual maturity onward male ranges from 168 to 675 kg (370 to 1,488 lb). According to Guinness Records the average male Kodiak bear is 2.44 m (8 ft 0 in) in total length (head-to-tail) and has a shoulder height of 1.33 m (4 ft 4 in). 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 (688 to 858 lb) with a mean body mass of 357 kg (787 lb) while the same figures in females were 202 to 256 kg (445 to 564 lb) with a mean body mass of 224 kg (494 lb). By the time they reach or exceed eight to nine years of age, male Kodiak bears tend to be much larger than newly mature 6-year-old males, potentially tripling their average weight within three years’ time, and can expect to average between 360 and 545 kg (794 and 1,202 lb). The reported mean adult body masses for both sexes of polar bear are very similar to the peninsular 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 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 (1,656 lb), 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 Kamchatka brown bear (U. a. beringianus). In the Kamchatka brown bear in past decades, old males have been known to reach body mass of 500–685 kg (1,102–1,510 lb) by fall, putting the subtypes 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 Kamchatka brown bears weighed merely between 150 and 285 kg (331 and 628 lb), however, mean weights of mature male bears have been reported as averaging 350 to 450 kg (770 to 990 lb) in 2005.

Subspecies 13

  1. Ursus arctos arctos
  2. Ursus arctos beringianus
  3. Ursus arctos collaris
  4. Ursus arctos crowtheri †
  5. Ursus arctos isabellinus
  6. Ursus arctos pruinosus
  7. Ursus arctos lasiotus
  8. Ursus arctos syriacus
  9. Ursus arctos alascensis
  10. Ursus arctos californicus †
  11. Ursus arctos dalli
  12. Ursus arctos gyas
  13. Ursus arctos horribilis
  14. Ursus arctos middendorffi
  15. Ursus arctos sitkensis
  16. Ursus arctos stikeenensis

Sources and Credits

  1. (c) Aleksandar, some rights reserved (CC BY-SA), uploaded by Aleksandar
  2. (c) Soldatnytt, some rights reserved (CC BY), http://commons.wikimedia.org/wiki/File:Ursus_arctos_-_Norway.jpg
  3. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Ursus_arctos_01_MWNH_145.JPG
  4. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Ursus_arctos_02_MWNH_145.JPG
  5. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Ursus_arctos_03_MWNH_145.JPG
  6. (c) Gunnar Ries, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:B%C3%A4renspurP1050395.jpg
  7. (c) Jan van der Crabben, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Bear-footprint.jpg
  8. Forest Service Northern Region, no known copyright restrictions (public domain), http://commons.wikimedia.org/wiki/File:Grizzly_Bear_Tracks_(7205001304).jpg
  9. Yellowstone National Park, no known copyright restrictions (public domain), http://commons.wikimedia.org/wiki/File:Grizzly_bear_tracks_(24405502311).jpg
  10. (c) ŠJů, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Medv%C4%9Bd%C3%AD_v%C3%BDkal.jpg
  11. (c) Walter Siegmund, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Scat_8616.JPG
  12. (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Brown_bear
  13. (c) Aleksandar, some rights reserved (CC BY-SA)

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