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Captive Brown Bear [Urso Pardo] (2019)

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Lisbon Zoological garden, Sete Rios, Lisbon, Portugal

ABOUT THE BROWN BEAR

The brown bear (Ursus arctos) is a bear that is found across much of northern Eurasia and North America. In North America, the populations of brown bears are often called grizzly bears. It is one of the largest living terrestrial members of the order Carnivora, rivalled in size only by its closest relative, the polar bear (Ursus maritimus), which is much less variable in size and slightly larger on average.

The brown bear’s principal range includes parts of Russia, Central Asia, China, Canada, the United States, Hokkaido, Scandinavia, and the Carpathian region, especially Romania, Anatolia and the Caucasus. The brown bear is recognized as a national and state animal in several European countries.

While the brown bear’s range has shrunk and it has faced local extinctions, it remains listed as a least concern species by the International Union for Conservation of Nature (IUCN) with a total population of approximately 200,000. As of 2012, this and the American black bear are the only bear species not classified as threatened by the IUCN. However, the California grizzly bear, Atlas bear and Mexican grizzly bear were hunted to extinction in the 19th and early 20th centuries and many of the southern Asian subspecies are highly endangered. One of the smaller-bodied subspecies, the Himalayan brown bear, is critically endangered, occupying only 2% of its former range and threatened by uncontrolled poaching for its body parts. The Marsican brown bear of central Italy is one of several currently isolated populations of the Eurasian brown bear and believed to have a population of just 40 to 50 bears.

EVOLUTION AND TAXONOMIC HISTORY

The brown bear is sometimes referred to as the bruin, from Middle English. This name originated in the fable, History of Reynard the Fox, translated by William Caxton, from Middle Dutch bruun or bruyn, meaning brown (the colour). In the mid-19th century the United States, the brown bear was termed "Old Ephraim" and sometimes as "Moccasin Joe".

The scientific name of the brown bear, Ursus arctos, comes from the Latin "Ursus", meaning "bear", and ἄρκτος "arktos", from the Greek word forbear.

GENERALIZED BROWN BEAR NAMES AND EVOLUTION

Brown bears are thought to have evolved from Ursus Etruscans in Asia. The brown bear, per Kurten (1976), has been stated as "clearly derived from the Asian population of Ursus savini about 800,000 years ago; spread into Europe, to the New World." Genetic analysis indicated that the brown bear lineage diverged from the cave bear species complex approximately 1.2–1.4 million years ago, but did not clarify if U. Savini persisted as a para species for the brown bear before perishing. The oldest fossils positively identified as from this species occur in China from about 0.5 million years ago. Brown bears entered Europe about 250,000 years ago and North Africa shortly after. Brown bear remains from the Pleistocene period are common in the British Isles, where it is thought they might have outcompeted cave bears (Ursus spelaeus). The species entered Alaska 100,000 years ago, though they did not move south until 13,000 years ago. It is speculated that brown bears were unable to migrate south until the extinction of the much larger giant short-faced bear (Arctodus simus).

Several palaeontologists suggest the possibility of two separate brown bear migrations: inland brown bears, also known as grizzlies, are thought to stem from narrow-skulled bears which migrated from northern Siberia to central Alaska and the rest of the continent, while Kodiak bears descend from broad-skulled bears from Kamchatka, which colonized the Alaskan peninsula. Brown bear fossils discovered in Ontario, Ohio, Kentucky and Labrador show the species occurred farther east than indicated in historic records. In North America, two types of the subspecies Ursus arctos horribilis are generally recognized—the coastal brown bear and the inland grizzly bear; these two types broadly define the range of sizes of all brown bear subspecies.

SCIENTIFIC BROWN BEAR TAXONOMY

There are many methods used by scientists to define bear species and subspecies as no one method is always effective. Brown bear taxonomy and subspecies classification have been described as "formidable and confusing" with few authorities listing the same specific set of subspecies. Genetic testing is now perhaps the most important way to scientifically define brown bear relationships and names. Generally, genetic testing uses the word clade rather than species because a genetic test alone cannot define a biological species. Most genetic studies report on how closely related the bears are (or their genetic distance). There are hundreds of obsolete brown bear subspecies, each with its own name, and this can become confusing; Hall (1981) lists 86 different types and even as many as 90 have been proposed. However, recent DNA analysis has identified as few as five main clades which contain all extant brown bears, while a 2017 phylogenetic study revealed nine clades, including one representing polar bears. As of 2005, 15 extant or recently extinct subspecies were recognized by the general scientific community.

As well as the exact number of overall brown bear subspecies, its precise relationship to the polar bear also remains in debate. The polar bear is a recent offshoot of the brown bear. The point at which the polar bear diverged from the brown bear is unclear, with estimations based on genetics and fossils ranging from 400,000 to 70,000 years ago, but most recent analysis has indicated that the polar bear split somewhere between 250,000 and 130,000 years ago. Under some definitions, the brown bear can be construed as the para species for the polar bear.

DNA analysis shows that, apart from recent human-caused population fragmentation, brown bears in North America are generally part of a single interconnected population system, with the exception of the population (or subspecies) in the Kodiak Archipelago, which has probably been isolated since the end of the last Ice Age. These data demonstrate that U. a. gyas, U. a. horribilis, U. a. sitkensis and U. a. stikeenensis are not distinct or cohesive groups, and would more accurately be described as ecotypes. For example, brown bears in any particular region of the Alaska coast are more closely related to adjacent grizzly bears than to distant populations of brown bears, the morphological distinction seemingly driven by brown bears having access to a rich salmon food source, while grizzly bears live at higher elevation, or further from the coast, where plant material is the base of the diet. The history of the bears of the Alexander Archipelago is unusual in that these island populations carry polar bear DNA, presumably originating from a population of polar bears that were left behind at the end of the Pleistocene, but have since been connected with adjacent mainland populations through movement of males, to the point where their nuclear genomes are now more than 90% of brown bear ancestry.

THE SUBSPECIES HAVE BEEN LISTED AS FOLLOWS:

PALEARCTIC REALM (EURASIA AND NORTH AFRICA)

URSUS ARCTOS ARCTOS – EURASIAN BROWN BEAR

Represents every population found in Europe as well as their range in western Russia and the Caucasus. May be found as far east in Russia as the Yenisei River in Yamalo-Nenets Autonomous Okrug to Novosibirsk Oblast in the south, where the subspecies intergrade into U. a. collars. A predominantly dark, richly brown coloured (with rare light-coloured individuals), moderately-sized subspecies with dark claws, the Eurasian brown bears occurring in Russia are larger than their European counterparts, which may be in part because they are hunted less.

URSUS ARCTOS BERINGIANUS – KAMCHATKA BROWN BEAR (OR FAR EASTERN BROWN BEAR)

Found in the coastal lands surrounding the Sea of Okhotsk down as far as the Shantar Islands, Kolyma, all the land around the Shelikhov Gulf, the Kamchatka Peninsula and Paramushir Island.

A very large bear with a broad muzzle. Overall has dark colouring, some animals appearing almost blackish-brown but will usually be paler at the top of the back. It may overlap with U. a. collars extensively a few miles inland. It is thought to be the ancestor of the polar bear, the Kodiak bear, and the peninsular brown bears of Alaska. Middendorf described it from Greater Shantar Island with its distribution range comprising the eastern coast of Siberia and Japan.

URSUS ARCTOS COLLARIS – EAST SIBERIAN BROWN BEAR

A majority of Siberia from the Yenisei River to as far south as the Altai Mountains in northern Mongolia, northernmost Xinjiang and northeastern Kazakhstan. Ranges as far north as the southwestern Taymyr Peninsula and the Anabar River. As the farthest east ranging of all Eurasian brown bear populations, it is found in Chukotka as far as the coast of the Bering Strait to the east and the coast of the Chukchi Sea in the north.

Most bears of this type are fairly dark, but some are as pale as grizzly bears. It is intermediate in size between U. a. arctos and U. a. beringianus, with a proportionately larger skull than the nominate subspecies. In the sub-Arctic region of Yakutia, bears are reportedly quite small compared to other regions.

URSUS ARCTOS CROWTHERI – †ATLAS BEAR (EXTINCT)

Habitat, while still extant, was the Atlas Mountains and adjacent areas in North Africa, from Morocco to Libya. The last surviving Atlas bear is thought to have been killed by hunters in 1890.

URSUS ARCTOS ISABELLINUS – HIMALAYAN BROWN BEAR

Northern Nepal, Northern and Northeastern India and Northern Pakistan, most continuous current range in Jammu and Kashmir.Quite distinctive physically, as it possesses a reddish-brown or sandy-brown coat colour with silver-tipped hairs and relatively large ears. This bear is smaller than most other brown bears found on the Asian continent. Prefers high altitude forests and alpine meadows. Critically Endangered.

URSUS ARCTOS PRUINOSUS – TIBETAN BLUE BEAR

Tibetan Plateau; some of the bears found in the Himalayas are reportedly actually wandering individuals from the more robustly populated Tibetan subspecies.[41][46]This is a moderately-sized subspecies with long, shaggy fur. Both dark- and light-colored variants are encountered, with intermediate colors predominating. The fur around the neck, chest and shoulders is yellowish-brown or whitish and frequently forms a collar which no other brown bear subspecies typically possesses in a mature state. Like the Himalayan brown bear, the ears are relatively prominent. The skull is distinguished by its relatively flattened choanae, an arch-like curve of the molar row and large teeth, probably in correlation to its, particularly carnivorous habits.[41]
Ursus arctos lasiotus – Ussuri brown bear (or Amur brown bear, black grizzly or horse bear)Ursus arctos lasiotus – Beijing Zoo 3.JPGRussia: the southern Kuril Islands, Sakhalin, the Maritime Territory and the Ussuri/Amur River region south of the Stanovoy Range, China (former Manchuria): Heilongjiang, Japan: Hokkaidō, Honshu (in the last glacial period), the Korean Peninsula: North Korea[41] Became extinct on Rebun and Rishiri Islands in the 13th century.[47]Ursus arctos lasiotus is quite variable in size. Skull dimensions from mainland Russia (i.e. the Primorsky and the Khabarovsk) indicate they can rival Kamchatka brown bears in size.[41][43] By contrast, the population found in Hokkaido is one of the smallest northern forms of the brown bear. Nonetheless, individuals from Hokkaido can reportedly get larger than expected and have reached 400 to 550 kg (880 to 1,210 lb).[48] in weight by feeding on cultivations.[49][50] This bear is thought to be the ancestor of U. a. horribilis.[17] It is perhaps the darkest-coloured population on average and some specimens are almost fully black in colour, although lighter brown and intermediate forms are known. Due to its colouring, this subspecies is sometimes informally referred to as the "black grizzly".
Ursus arctos syriacus – Syrian brown bearUrsus arctos syriacus.jpgTranscaucasia, Iraq, Turkey (Asia Minor), Iran, western Afghanistan, eastern Lebanon, Pakistan, western Himalayas and the Pamir-Alay and Tien Shan mountains.[41] Despite a historical presence in Israel and the Syrian Arab Republic (the subspecies’ namesake), it is believed to be extinct in these countries now.[1]The Syrian brown bear is a moderate- to small-sized subspecies with light claws. This population tends to be a whitish-blond color with less noticeable black-based hairs than grizzly bears have.[41]
Ursus arctos priscus – Steppe brown bear (extinct)UnavailableEurasiaThe steppe brown bear was a extinct prehistoric brown bear subspecies that lived in places like Slovakia.
Nearctic realm (North America)[edit]
Subspecies nameImageDistributionDescription/comments
Ursus arctos californicus – †California grizzly bear (extinct)Monarch the bear.jpgCalifornia, mainly in the Sierra Nevadas and some areas of coastal California.The last known California grizzly bear was shot in California in 1922. Museum specimens illustrate that this population was golden-blonde overall typically without the contrasting black fur base of true grizzly bears. It also appeared to have been considerably larger, with a broader muzzle than true grizzly bears.[51]
Ursus arctos dalli – Dall Island brown bearDall Island, Alaska.Poorly described; possibly merely a coastal variation of other North American brown bears, but any such alliance is genetically ambiguous.[52][53]
Ursus arctos gyas – Alaska Peninsula brown bearBrown bear.jpgCoastal Alaska from the Aleutian Islands as far west as Unimak, the Alaska Peninsula to the Kenai Peninsula.Considered by some biologists to be the same subspecies as U. a. middendorffi.[54] Based on known size of adult males, if it is a true subspecies, it may match or exceed the Kodiak bear in size.[55][56]
Ursus arctos horribilis – Grizzly bearGrizzly Bear Yellowstone.jpgMost of Alaska, Yukon, the Northwest Territories, British Columbia, western Alberta, northern Idaho, western Montana, and northwestern Wyoming.The grizzly bear is identified by a medium to dark brown coat with gray or blond "grizzled" tips on the fur, which contrast with the black base. Highly variable in size, based largely on environmental conditions.[57] It is also highly adaptable: it can live in montane pine forests, temperate rainforest, semi-arid scrubland, tundra and shortgrass prairie.[58]
Ursus arctos middendorffi – Kodiak bearBear Square.JPGKodiak, Afognak and Shuyak Islands (Alaska), arguably includes other coastal Alaskan forms, which occur in most of the coasts of the western and southern parts of the state.This is the largest distinct subspecies of the brown bear, though the coastal-living members of other brown bear subspecies potentially rival it in size. It is medium-hued, typically not as dark as most forms from eastern Asia, but distinctly darker than grizzly bears.
Ursus arctos sitkensis – Sitka brown bearSitka brown bear.jpgAdmiralty Island, Baranof Island and Chichagof Island, the "ABC Islands" of Alaska.Appearing to be more closely related to the polar bear than to other brown bears, although it is on average the most dark-colored population in North America, with similar body size to grizzly bears from interior Alaska.[38][53] This subspecies is called "clade II" by Waits and others and is part of the former subspecies identified as U. a. sitkensis by Hall and as U. a. dalli by Kurtén.
Ursus arctos stikeenensis – Stickeen brown bearNorthwestern British Columbia[59] from the Stikine River to the Skeena River.[60]Variously recognised as a distinct subspecies[30][59] or as belonging to the subspecies U. a. horribilis.[38][51] Larger than most other grizzly bear populations, with males approaching the great bears of coastal Alaska in size.[61][62]
Ursus arctos (Ungava population) – †Ungava brown bear (extinct)Ungava Cabot 1910 Cropped.jpgNorthern Quebec and Labrador[63]Historical reports of brown bears in Quebec were typically dismissed by modern biologists. In 1975, anthropologist Steven Cox discovered a brown bear skull in Labrador, confirming that the population did once exist.[64]
Hybrids[edit]
Main article: Grizzly–polar bear hybrid
A grizzly–polar bear hybrid (known either as a pizzly bear or a grolar bear) is a rare ursid hybrid resulting from a crossbreeding of a brown bear and a polar bear. It has occurred both in captivity and in the wild. In 2006, the occurrence of this hybrid in nature was confirmed by testing the DNA of a strange-looking bear that had been shot in the Canadian Arctic, and seven more hybrids have since been confirmed in the same region, all descended from a single female polar bear.[65] Previously, the hybrid had been produced in zoos and was considered a "cryptid" (a hypothesized animal for which there is no scientific proof of existence in the wild).

Analyses of the genomes of bears have shown that introgression between species was widespread during the evolution of the genus Ursus,[66][67][68] including the introgression of polar bear DNA introduced to brown bears during the Pleistocene.

Formerly considered subspecies[edit]
Former
subspecies nameImageDistributionDescription
Ursus arctos gobiensis – Gobi bearUrsus arctos gobiensis.jpgGobi DesertAn extremely rare bear found in the Gobi Desert, this bear is adapted to desert life, dwelling in oases and rocky outcrops. It is rather small and pale and it appears to lack the whitish collar characteristic of Tibetan blue bears.[69][70] Phylogenetic analysis suggests they represent a relict population of the Himalayan brown bear.[71][29] At one time, Gobi bears probably overlapped and possibly interbred with Tibetan blue bears in western China, but the bears are now extinct in this area.[72]
Ursus arctos marsicanus – Marsican brown bear or Apennine brown bear[73]Orso bruno marsicano.jpgMarsica, central ItalyThere are an estimated 40 to 50 bears remaining in the Marsican area. This is an unrecognized subspecies that is now considered to be a population of the nominate subspecies.[30]
Ursus arctos nelsoni – †Mexican grizzly bear (extinct)Mexico grizzlies.pngThe smallest North American brown bear, formerly from northern Mexico, including Chihuahua, Coahuila and Sonora and southwestern United States, including the southern regions of Arizona, New Mexico and TexasThis bear is believed to have been hunted to extinction due to its interference with cattle ranching in both the United States and Mexico. Scarce by the 1930s, the last recorded sighting was in 1962.[74] Distinct in its ability to survive arid conditions, it could live in both montane pine forests of Mexico and canyonlands adjacent to the Sonoran Desert.
Ursus arctos pyrenaicus – Cantabrian brown bear or Iberian brown bear, now considered to be the same subspecies as the Eurasian brown bear (Ursus arctos arctos)See photographs in Eroski article (in Spanish, also available in Catalan, Basque and Galician) and in Fauna Ibérica. Oso pardo ibérico (Ursus arctos pyrenaicus), in SpanishIberian Peninsula, primarily the Cantabrian Mountains and hills in Galicia, and the Pyrenees.[75] Rare, sporadic sightings in northern Portugal.[76]Until recently, this bear was considered a separate subspecies. Today, it is considered to belong to the subspecies U. a. arctos. Scientific evidence based on DNA studies would furthermore indicate the Eurasian brown bear can be divided into two distinct lineages. "There is a clear division into two main mitochondrial lineages in modern Eurasian brown bear populations. These populations are divided into those carrying an eastern lineage (clade IIIa, Leonard et al. 2000), which is composed of Russian, northern Scandinavian and eastern European populations, and those carrying a western lineage (clade I, Leonard et al. 2000), which is composed of two subgroups, one believed to originate from the Iberian Peninsula, including southern Scandinavian bears and the Pyrenean populations; and the other from the Italian–Balkan peninsulas (Taberlet et al. 1994; see however Kohn et al. 1995). In addition, based on the subfossil record in northwestern Moldova and mitochondrial DNA data from modern populations, a Carpathian refuge has also been proposed (Sommer & Benecke 2005; Saarma et al. 2007)."[77]
The Cantabrian brown bear is the largest wild animal on the Iberian Peninsula, although it is also one of the smallest of the brown bears, weighing between 92 and 180 kg (203 and 397 lb) as an adult.[78] Its fur varies from pale cream to dark brown, but always with a distinctively darker, nearly black tone at the paws and a yellowish tinge at the tip of each hair. The Cantabrian brown bear population in Spain is considered endangered.

The Cantabrian brown bear population in the Pyrenees stems mostly from bears reintroduced from Slovenia, with one or two remaining original males.[75][77][79][80][81]

Description[edit]

Brown bear claws are longer and less curved than those of black bears
Color of brown bears[edit]

Brown bear on a rock
Brown bears are often not fully brown.[82] They have long, thick fur, with a moderately long mane at the back of the neck which varies somewhat across the types.[83] In India, brown bears can be reddish with silver-tipped hairs, while in China brown bears are bicolored, with a yellowish-brown or whitish collar across the neck, chest and shoulders.[82][84] Even within well-defined subspecies, individuals may show highly variable hues of brown. 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. Apart from the cinnamon subspecies of the American black bear (U. americanus cinnamonum), the brown bear is the only modern bear species to typically appear truly brown.[44] 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.[41]

Claws and feet[edit]

Front paws of a brown bear
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.[85] They are generally dark with a light tip, with some forms having completely light claws.[41] Brown bear claws are longer and straighter than those of American black bears (Ursus americanus).[44] 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.[86] 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.[21][87] 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.[88][89][90] Brown bears are the only extant bears with a hump at the top of their shoulder, which is 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.[44][91]

Cranial morphology and size[edit]

Brown bear skull
Adults have massive, heavily built concave skulls, which are large in proportion to the body. The forehead is high and rises steeply.[44] 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.[41] Grizzlies, for example, tend to have flatter profiles than European and coastal American brown bears.[92] Skull lengths of Russian brown 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.[41] 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.[41] 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 the 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.[93][94] The teeth are reliably larger than American black bears, but average smaller in molar length than polar bears.[95][96] Brown bears have the broadest skull of any extant ursine bear; only the aforementioned most herbivorous living bears exceed them in relative breadth of the skull.[7][97][98] 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.[44][98]

Body size[edit]

Brown bears are highly variable in size. Eurasian brown bears often fall around the middle to low sizes for the species.
The brown bear is the most variable in size 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.[99][100]

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.[101][102] 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.[5][7][103] Interior brown bears are generally smaller than is often perceived, being around the same weight as an average 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.[7][104] 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).[7][97][105][106]

Ecotypes or regional populations[edit]
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.[7][97][107] 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. 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 (121 to 386 lb) on average.[7][105][108][109][110] 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.[7]

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.[97][111] Even elsewhere in Alberta, weights averaging more than twice those of Jasper grizzlies have been recorded.[112] 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.[7][97][113] 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.[43][114][115]

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).[90][116] 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.[117][118] 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.[119] 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.[9][89][117][118] 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.[89]

An Ussuri brown bear of Hokkaido, a relatively small-bodied population, in the snow
In Eurasia, the size of bears roughly increases from the west to the east, with the largest bears there native to eastern Russia.[120] 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).[121][122] 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.[41][43] In some cases, the big adult males of these populations may have matched the Kodiak bear in size.[41] 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.[53][123] 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.[124][125] 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.[43]

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.[26] Bears from the Syrian subspecies (U. a. syriacus) will reportedly weigh around 100 to 160 kg (220 to 350 lb) in adulthood.[126] The Himalayan brown bear (U. a. isabellinus) is another rival for the smallest subspecies, in Pakistan this subtype averages about 70 kg (150 lb) in females and 135 kg (298 lb) in males.[127] Himalayan brown bear females were cited with an average head-and-body length of merely 1.4 m (4 ft 7 in).[128] 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.[7][70] These smallest brown bear subtypes are characteristically found in "barren-ground" type habitats, i.e. sub-desert in bears from the Syrian subspecies and the Gobi subtype and arid alpine meadow in Himalayan brown bears.[7][70][127]

Considering pinnipeds[129] and polar bears[5][7][103] to be marine, the Kodiak bear is the largest[130][131] of the living, land-based, mammalian predators.
The largest subspecies are the Kodiak bear (U. a. middendorffi) and the questionably-distinct peninsular or coastal brown bear (U. a. gyas).[7][132][133][133] Also the extinct California grizzly bear (U. a. californicus) was rather large.[26][134] Once mature, the typical female Kodiak bear can range in body mass from 120 to 318 kg (265 to 701 lb) and from sexual maturity onward males range from 168 to 675 kg (370 to 1,488 lb).[7][133][135][136] According to the Guinness Book of World 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).[89] 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).[97][136][137][138][139] 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 (794 and 1,202 lb).[89][90][135] 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 largest extant terrestrial carnivores.[89][140][141] 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.[5][89][142] 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.[44][143]

The largest variety of brown bear from Eurasia is the Kamchatka brown bear (U. a. beringianus). In the Kamchatka brown bears from 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.[144][145][146] 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.[123][144][145]

Distribution[edit]
Brown bears were once native to much of Asia, some parts of the Atlas Mountains of Africa and perhaps most of Europe and North America,[147] but are now extinct in some areas and their populations have greatly decreased in other areas.[2][83] There are approximately 200,000 brown bears left in the world.[148] The largest populations are in Russia with 120,000,[149] the United States with 32,500, Canada with around 25,000 and Romania with around 5,000. The brown bear currently occurs in the countries of Afghanistan, Albania, Andorra (recently reoccupied), Armenia, Azerbaijan, Belarus, Bhutan (possibly extinct), Bosnia and Herzegovina, Bulgaria, Canada, China, Croatia, Czech Republic (possibly only vagrants), Estonia, Finland, France, Georgia, Greece, India, Iran, Iraq, Italy, Japan, Kazakhstan, Kyrgyzstan, Latvia (extinct before World War II; possibly vagrants from Estonia or Russia after World War II), North Macedonia, Mongolia, Montenegro, India, Nepal, North Korea, Norway, Pakistan, Poland, Romania, Russia, Serbia, Slovakia, Slovenia, Spain, Sweden, Tajikistan, Turkey, Turkmenistan, Ukraine, the United States and Uzbekistan.[1]

Brown bear at Brooks Falls in Katmai National Park
North America[edit]
The brown bear is usually called the grizzly bear in North America. It once ranged throughout much of the western part of the continent.[2][150]

Canada[edit]
As many as 20,000 brown bears range throughout Yukon, the Northwest Territories, British Columbia and in the majority of Alberta. Canada has one of the most stable brown bear populations today. They reach their current eastern limits of their distribution in North America in a majority of Nunavut, northeastern Saskatchewan and northern Manitoba, where they range as far east as the west coast of the Hudson Bay from around Rankin Inlet south to Southern Indian Lake.[1][2][150]

United States[edit]
The brown bear has lost 98% of its habitat in the lower 48 states. About 95% of the brown bear population in the United States is in Alaska, though in the lower 48 states, they are repopulating gradually but steadily along the Rockies and the western Great Plains.[151][152] The Alaskan population is estimated at 32,000 individuals.[153] The largest populations of brown bears in the lower 48 states are found in the 23,300 square kilometre Greater Yellowstone Ecosystem and the 24,800-square kilometre Northern Continental Divide Ecosystem.[154] The Greater Yellowstone Ecosystem of northwest Wyoming is estimated to hold about 674–839 grizzly bears, followed slightly by the Northern Continental Divide Ecosystem of northwest Montana with about 765 animals, the Cabinet-Yaak Ecosystem of northwest Montana and northeast Idaho with about 42–65 animals, the Selkirk Ecosystem of northeast Washington and northwest Idaho with only about 40–50 animals, and (even less) the North Cascades Ecosystem of north-central Washington with about five to 10 animals.[155][156][157][158]

Group of brown bears at Brooks Falls
These five ecosystems combine for a total of a maximum 1,729 wild grizzlies still persisting in the contiguous United States. Unfortunately, these populations are isolated from each other, inhibiting any genetic flow between ecosystems and creating low genetic diversity in remaining populations which can have negative long-term effects.[154][159] This isolation poses one of the greatest threats to the future survival of the grizzly bear in the contiguous United States.[154] Although there is no record of their existence in the United States east of the Rocky Mountain and Great Plains regions (except for a relic population in the Ungava Peninsula which survived until the dawn of the 20th century) in human history, fossil records from Kentucky do in fact show that grizzly bears once roamed in eastern North America.[160]

Mexico[edit]
Although many people believe some brown bears may be present in Mexico, they are almost certainly extinct there.[161] The last Mexican grizzly bear was shot in 1976.[162] Prior to the 1976 record, none have been seen since at least 1962.

Europe[edit]

Bear watching hut in Alutaguse, Estonia. There are around 700 bears in Estonia and they are especially numerous in the Alutaguse forests.
In Europe, there are 14,000 brown bears in 10 fragmented populations. They are extinct in the British Isles, extremely threatened in France and Spain and in trouble over most of Central Europe.[9][83]

Brown bears reach their western limits in Spain. In the Cantabrian Mountains of northwestern Spain, some 210 bears were found to dwell in Asturias, Cantabria, Galicia and León, in the Picos de Europa and adjacent areas in 2013.[163] As of 2015, this population was estimated at around 250 individuals, but only due to it being a more extensive survey and their numbers may be declining rather than increasing.[164] However, the population of brown bears in the Pyrenees Mountains, in a range shared between France, Spain and Andorra, is much lower, estimated at 14 to 25, with a shortage of breeding females.[1][165][166][167] Their rarity in this area has led biologists to release bears, mostly females, from Slovenia in spring 2006 to reduce the imbalance and preserve the species’ presence in the area. The bears were released despite protests from French farmers.[168][169] By 2017 the bears in the Pyrenean region had increased to 39, including 10 cubs.[170]

A small population of brown bears (formerly assigned to the subspecies Ursus arctos marsicanus, which is now considered part of the nominate subspecies) still lives in central Italy (the Apennine Mountains, Abruzzo and Latium), with no more than 70 individuals, protected by strong laws, but endangered by the human presence in the area.[73][171]

In eastern and northern Europe, the range of the brown bear currently extends more broadly. Among the most populous countries for brown bears in the eastern region are Romania, which has approximately 4,000–5,000 brown bears, Bulgaria with 900–1,200, Slovakia at about 600–800 bears, Slovenia at approximately 500–700 animals and Greece at about 450[172] animals in the south. The Carpathian brown bear population of Romania is the largest in Europe outside of Russia. Despite the relatively large size of the country’s bear population, the species’ numbers there were declining alarmingly due to overhunting before Romania’s EU membership (which also depended on the protection of the brown bear in the country).[173] Reported annual population growth rates were frequently greater than maximum published growth rates, which could lead to unsustainable hunting.[174] In July 2017, the Romanian Ministry of Environment released an order for the hunting of 175 bears that year because of either the increasing bear population or changes in animal behavior because of destruction of habitat by deforestation, causing an increase in attacks on humans and damage caused by bears to local communities.[175] There is also a smaller brown bear population in the Carpathian Mountains in Ukraine (estimated at about 200 in 2005), Slovakia and Poland (estimated at about 170 in 2009 in the latter country).[176] The total Carpathian population is estimated at about 8,000.[177]

Northern Europe is home to a large brown bear population, with an estimated 2,500 (range 2,350–2,900) in Sweden, about 2,200 in Finland,[178] about 700 in Estonia and 70 in Norway, totaling to nearly 5,000 individuals in the wild. Another large and relatively stable population of brown bears in Europe, consisting of 2,500–3,000 individuals, is the Dinaric-Pindos (Balkans) population, with contiguous distribution in northeast Italy, Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, North Macedonia, Albania, Bulgaria and Greece.[179][180] Brown bears inhabited the mountains of Austria until as recently as 2011, after a reintroduction effort failed and the species became extinct again. There is currently no effort to reintroduce the species into Austria.[181] The entire alpine population of brown bears includes about 50 individuals, most of them living in the Adamello Brenta nature park in Italy. Reintroduction of 10 Slovenian brown bears to the Trentino area in 1998 and 2002 produced occasional visitors to the South Tirol, the Swiss Eastern Alps, Bavaria and isolated sightings in the Central Alps. The small group of brown bears living in the Slovenian Alps is connected to the larger Dinaric-Pindos population.[182]

Asia Minor, the Caucasus, the Middle East and Central Asia[edit]
In this part of the world, the brown bear occurs from Georgia, Armenia and Azerbaijan southbound spottily through Turkey, northernmost Iraq, western and northern Iran, thence discontinuously in northeastern Kazakhstan, southeastern Uzbekistan and north to Kyrgyzstan. The populations in these countries are generally very small and fragmented, thus they are at high risk of genetic isolation and they occupy only small segments of their former range here.[1][183] At least 20-30 were present in Central Alborz Protected Area in northern Iran as of 2015.[184][185]

South Asia[edit]
In the Nepal Himalayas, the brown bear occurs in Manaslu Conservation Area.[186] It possibly persists in northern Bhutan and northern Myanmar, but is not confirmed to be present in these nations today.[187][188]

East Asia[edit]
In Asia, brown bears are found in nearly every part of Russia, thence to the southeast in a small area of Northeast China, western China and parts of North Korea. Further west, they reach the southern limits of their worldwide distribution, dwelling spottily in northern Pakistan, Afghanistan and the northern areas of India particularly in Jammu and Kashmir and Himachal Pradesh.[1]

Three distinct lineages of the Hokkaido brown bear (formerly Ursus arctos yesoensis; now considered the same subspecies as the Ussuri brown bear (U. a. lasiotus)) can also be found on the Japanese island of Hokkaido.[189][190] Hokkaido has the largest number of non-Russian brown bears in eastern Asia with about 2,000–3,000 animals,[88] although, in 2015, the Biodiversity Division of the Hokkaido government estimated the population as being as high as 10,600.[191]

Africa north of the Sahara Desert[edit]
Many people hold the belief that some brown bears may be present in the Atlas Mountains of Morocco, but there have been none sighted since the 19th century.[192] In addition to the native Atlas bear (U. a. crowtheri), the Romans apparently imported bears from Spain for spectacles with some escaping and founding a population in Africa, though it is doubtful that they still persist today.[28]

Habitat[edit]

Eurasian brown bears are often adapted to wooded and montane habitats
This species inhabits the broadest range of habitats of any living bear species.[88] They seem to have no altitudinal preferences and have been recorded from sea level to an elevation of 5,000 m (16,000 ft) (the latter in the Himalayas).[88][193] In most of their range, brown bears generally seem to prefer semi-open country, with a scattering of vegetation that can allow them a resting spot during the day. However, they have been recorded as inhabiting every variety of northern temperate forest known to occur.[88] North American brown bears, or grizzly bears, generally seem to prefer open or semi-open landscapes, with the species once having been common on the Great Plains and continue to occur in sizeable numbers in tundra and coastal estuaries and islands. Variable numbers still occur in prairie areas of the northern Rocky Mountains (mostly in Canada, but some in the contiguous United States). Where continuous and protected, such as the Greater Yellowstone Ecosystem, the prairie is near-ideal interior habitat for the species.[21][88]

In western Eurasia, they inhabit mostly mountainous woodlands, in ranges such as the Alps, the Pyrenees and the Caucasus, though they may have been driven into more wooded, precipitous habitats due to the prior extensive persecution of the species in some regions.[143] [194] Desolate parts of northern and eastern Europe, like large patches of Scandinavia and the Carpathian Mountains, have always been quite heavily forested and have maintained relatively stable populations of brown bears, indicating that the bears here are well-adapted to forest-dwelling, although they generally seek foraging opportunities in forest openings such as bogs.[88][195] In general, enclosed forest is sub-standard foraging habitat for brown bears and so they occur irregularly in true taiga lands, despite the boreal forest falling at the middle of their circumpolar distribution.[196]

In Central Asia, human disturbances are minimal as this area has a harsher environment and is more sparsely populated. In this part of the world, bears may be found in steppe, which is sparser and more desert-like than grassland habitats in North America that occur at similar latitudes and some bears may live out their lives even in desert edge, such as those that live in the Middle East (Syrian brown bears) and the rare Gobi bear which is native only to the Chinese-Mongolian desert of its name and isolated from other populations.[83][146][185][197] Alpine meadows are the typical habitat in the Himalayan brown and Tibetan blue subspecies of brown bear.[193][198][199] In Siberia, the species seems well-adapted to living in almost all parts of the extensive pine forests, usually coming to waterways or poorly drained openings and bogs while feeding and sheltering in broad roots and trunks in the interior.[145][146] Eastern Russian forests hold arguably the largest number of brown bears in the world, outside of possibly Alaska and northwestern Canada.[88][146] The brown bears of Hokkaido are also largely forest-dwelling, but dwell in mixed forests dominated by broadleaf trees such as beech.[189][200]

It is thought the Eurasian brown bears which colonized America were tundra-adapted (as many grizzlies are today in North America) and the species is sometimes found around sub-Arctic ice fields. This is indicated by brown bears in the Chukotka Peninsula on the Asian side of the Bering Strait, which are the only Asian brown bears to live year-round in lowland tundra like their North American cousins.[201][202][203] Genetics relay that two separate radiations led to today’s North American brown bears, one a coastal form that led to the Kodiak bear (from U. a. beringianus or a common ancestor) and one an interior form that led to the grizzly bear (from U. a. lasiotus or a common ancestor).[17] In Arctic areas, the potential habitat of the brown bear is increasing. The warming of that region has allowed the species to move farther north into what was once exclusively the domain of the polar bear (potentially another offshoot of a radiation of coastal brown bears). In non-Arctic areas, habitat loss is blamed as the leading cause of endangerment, followed by hunting.[204][205][206]

Conservation status[edit]
While the brown bear’s range has shrunk and it has faced local extinctions, it remains listed as a Least concern species by the IUCN, with a total population of approximately 200,000. As of 2012, this and the American black bear are the only bear species not classified as threatened by the IUCN.[1][2] However, the California grizzly bear, Atlas bear and Mexican grizzly bear, as well as brown bear populations in the Pacific Northwest, were hunted to extinction in the 19th and early 20th centuries and many of the southern Asian subspecies are highly endangered.[51] The Syrian brown bear (Ursus arctos syriacus) is very rare and it has been extirpated from more than half of its historic range.[207] One of the smallest-bodied subspecies, the Himalayan brown bear (Ursus arctos isabellinus), is critically endangered, occupying only 2% of its former range and threatened by uncontrolled poaching for its body parts.[11] The Marsican brown bear in central Italy is believed to have a population of just 30-40 bears.

Regional extinctions[edit]
The brown bear is extinct in Algeria, Belgium, Denmark, Egypt, Germany, Hungary, Ireland, Israel, Jordan, Lebanon, Liechtenstein, Lithuania, Luxembourg, Libya, Mexico, Moldova, Monaco, Morocco, the Netherlands, San Marino, Switzerland, Syria, Tunisia and the United Kingdom. It is possibly extinct in Bhutan.[1]

Behavior and life history[edit]

Like all bears, brown bears can stand on their hindlegs and walk for a few steps in this position, usually motivated to do so by curiosity, hunger or alarm
The brown bear is often described as nocturnal. However, it frequently seems to peak in activity in the morning and early evening hours.[208] Studies have shown that activity throughout the range can occur at nearly any time of night or day, with bears who dwell in areas with more extensive human contact being more likely to be fully nocturnal. Furthermore, yearling and newly independent bears are more likely to be active diurnally and many adult bears in low-disturbance areas are largely crepuscular.[209][210][211] In summer through autumn, a brown bear can double its weight from the spring, gaining up to 180 kg (400 lb) of fat, on which it relies to make it through winter, when it becomes very lethargic.[212][213] Although they are not full hibernators and can be woken easily, both sexes like to den in a protected spot during the winter months. Hibernation dens may consist of any spot that provides cover from the elements and that can accommodate their bodies, such as a cave, crevice, cavernous tree roots, or hollow logs.[214][215]

Brown bears have one of the largest brains of any extant carnivoran relative to their body size and have been shown to engage in tool use (e.g., using a barnacle-covered rock to scratch its neck), which requires advanced cognitive abilities.[216] This species is mostly solitary, although bears may gather in large numbers at major food sources (e.g., moth colonies, open garbage dumps or rivers holding spawning salmon) and form social hierarchies based on age and size.[217][218] Adult male bears are particularly aggressive and are avoided by adolescent and subadult males, both at concentrated feeding opportunities and chance encounters. Female bears with cubs rival adult males in aggression and are much more intolerant of other bears than single females. Young adolescent males tend to be least aggressive and have been observed in nonantagonistic interactions with each other.[219][220] Dominance between bears is asserted by making a frontal orientation, showing off canines, muzzle twisting and neck stretching to which a subordinate will respond with a lateral orientation, by turning away and dropping the head and by sitting or lying down.[221] During combat, bears use their paws to strike their opponents in the chest or shoulders and bite the head or neck. In his Great Bear Almanac, Gary Brown lists 11 different sounds bears produce in nine different contexts. Sounds expressing anger or aggravation include growls, roars, woofs, champs and smacks, while sounds expressing nervousness or pain include woofs, grunts and bawls. Sows will bleat or hum when communicating with their cubs.[44]

Home ranges[edit]
Brown bears usually occur over vast home ranges; however, they are not highly territorial. Several adult bears often roam freely over the same vicinity without issue, unless rights to a fertile female or food sources are being contested.[7][220] Males always cover more area than females each year. Despite their lack of traditional territorial behavior, adult males can seem to have a "personal zone" in which other bears are not tolerated if they are seen.[222] Males always wander further than females, due to both increasing access to females and food sources, while females are advantaged by smaller territories in part since it decreases the likelihood of encounters with male bears who may endanger their cubs.[7][91][97][223] In areas where food is abundant and concentrated, such as coastal Alaska, home ranges for females are up to 24 km2 (9.3 sq mi) and for males are up to 89 km2 (34 sq mi). Similarly, in British Columbia, bears of the two sexes travel relatively compact home ranges of 115 km2 (44 sq mi) and 318 km2 (123 sq mi). In Yellowstone National Park, home ranges for females are up to 281 km2 (108 sq mi) and up to 874 km2 (337 sq mi) for males. In Romania, the largest home range was recorded for adult males (3,143 km2, 1214 sq mi).[224] In the central Arctic of Canada, where food sources are quite sparse, home ranges range up to 2,434 km2 (940 sq mi) in females and 8,171 km2 (3,155 sq mi) in males.[7][88][91][220]

A study of male-inherited Y chromosome DNA sequence found that brown bears, over the past few 10,000 years, have shown strong male-biased dispersal.[225] That study found surprisingly similar Y chromosomes in brown bear populations as far apart as Norway and coastal Alaska, indicating extensive gene flow across Eurasia and North America. Notably, this contrasts with genetic signals from female-inherited mitochondrial DNA (mtDNA), where brown bears of different geographic regions typically show strong differences in their mtDNA, a result of female philopatry.

REPRODUCTION

Pair of mating brown bears at the Ähtäri Zoo in Ähtäri, Finland
The mating season is from mid-May to early July, shifting later the further north the bears are found.[88][97][226] Being serially monogamous, brown bears remain with the same mate from a couple of days to a couple of weeks.[7][227] Outside of this narrow time frame, adult male and female brown bears show no sexual interest in each other.[7] Females mature sexually between the age of four and eight years of age, with an average age at sexual maturity of 5.2–5.5 years old, while males first mate about a year later on average, when they are large and strong enough to successfully compete with other males for mating rights.[158][222][228] Males will try to mate with as many females as they can; usually a successful one mates with two females in a span of one to three weeks.[102][228] The adult female brown bear is similarly promiscuous, mating with up to four, rarely even eight, males while in heat and potentially breeding with two males in a single day. Females come into oestrus on average every three to four years, with a full range of 2.4 to 5.7 years. The urine markings of a female in oestrus can attract several males via scent.[91][97][127][223][229] Paternity DNA tests have shown that up to 29% of cubs in a litter will be from two to three different males.[223] Dominant males may try to sequester a female for her entire oestrus period of approximately two weeks, but usually are unable to retain her for the entire time.[97][223] Copulation is vigorous and prolonged and can last up to an hour, although the mean time is about 23–24 minutes.[97][230]

Grizzly bear cubs often imitate their mothers closely
Males take no part in raising their cubs – parenting is left entirely to the females.[220][231] Through the process of delayed implantation, a female’s fertilized egg divides and floats freely in the uterus for six months. During winter dormancy, the fetus attaches to the uterine wall. The cubs are born eight weeks later while the mother sleeps. If the mother does not gain enough weight to survive through the winter, the embryo does not implant and is reabsorbed into the body.[158][232][233] There have been cases of brown bears with as many as six cubs, although the average litter size is one to three, with more than four being considered uncommon.[158][234][235] There are records of females sometimes adopting stray cubs or even trading or kidnapping cubs when they emerge from hibernation (a larger female may claim cubs away from a smaller one).[88][236][237] Older and larger females within a population tend to give birth to larger litters[238] The size of a litter also depends on factors such as geographic location and food supply.[239] At birth, the cubs are blind, toothless and hairless and may weigh from 350 to 510 g (0.77 to 1.12 lb), again reportedly based on the age and condition of the mother.[240] They feed on their mother’s milk until spring or even early summer, depending on climate conditions. At this time, the cubs weigh 7 to 9 kg (15 to 20 lb) and have developed enough to follow her over long distances and begin to forage for solid food.[116][241]

Kodiak bear cubs play-fighting
The cubs are fully dependent on the mother and a close bond is formed. During the dependency stage, the cubs learn (rather than inherit as instincts from birth) survival techniques, such as which foods have the highest nutritional value and where to obtain them; how to hunt, fish and defend themselves; and where to den.[91] Increased brain size in large carnivores has been positively linked to whether a given species is solitary, as is the brown bear, or raises their offspring communally, thus female brown bears have relatively large, well-developed brains, presumably key in teaching behavior.[242] The cubs learn by following and imitating their mother’s actions during the period they are with her.[243] Cubs remain with their mother for an average of 2.5 years in North America, uncommonly being independent as early as 1.5 years of age or as late as 4.5 years of age.[97] The stage at which independence is attained may generally be earlier in some parts of Eurasia, as the latest date which mother and cubs were together was 2.3 years, most families separated in under two years in a study from Hokkaido and in Sweden most cubs on their own were still yearlings.[124][244] Brown bears practice infanticide, as an adult male bear may kill the cubs of a female bear.[223] When an adult male brown bear kills a cub, it is usually because he is trying to bring the female into oestrus, as she wil