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Brief Summary

    Bear: Brief Summary
    provided by wikipedia
    This article is about the carnivoran mammals. For other uses, see Bear (disambiguation).

    Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Northern Hemisphere and partially in the Southern Hemisphere. Bears are found on the continents of North America, South America, Europe, and Asia. Common characteristics of modern bears include large bodies with stocky legs, long snouts, small rounded ears, shaggy hair, plantigrade paws with five nonretractile claws, and short tails.

    While the polar bear is mostly carnivorous, and the giant panda feeds almost entirely on bamboo, the remaining six species are omnivorous with varied diets. With the exception of courting individuals and mothers with their young, bears are typically solitary animals. They may be diurnal or nocturnal and have an excellent sense of smell. Despite their heavy build and awkward gait, they are adept runners, climbers, and swimmers. Bears use shelters, such as caves and logs, as their dens; most species occupy their dens during the winter for a long period of hibernation, up to 100 days.

    Bears have been hunted since prehistoric times for their meat and fur; they have been used for bear-baiting and other forms of entertainment, such as being made to dance. With their powerful physical presence, they play a prominent role in the arts, mythology, and other cultural aspects of various human societies. In modern times, bears have come under pressure through encroachment on their habitats and illegal trade in bear parts, including the Asian bile bear market. The IUCN lists six bear species as vulnerable or endangered, and even least concern species, such as the brown bear, are at risk of extirpation in certain countries. The poaching and international trade of these most threatened populations are prohibited, but still ongoing.

Comprehensive Description

    Bear
    provided by wikipedia
    This article is about the carnivoran mammals. For other uses, see Bear (disambiguation).

    Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Northern Hemisphere and partially in the Southern Hemisphere. Bears are found on the continents of North America, South America, Europe, and Asia. Common characteristics of modern bears include large bodies with stocky legs, long snouts, small rounded ears, shaggy hair, plantigrade paws with five nonretractile claws, and short tails.

    While the polar bear is mostly carnivorous, and the giant panda feeds almost entirely on bamboo, the remaining six species are omnivorous with varied diets. With the exception of courting individuals and mothers with their young, bears are typically solitary animals. They may be diurnal or nocturnal and have an excellent sense of smell. Despite their heavy build and awkward gait, they are adept runners, climbers, and swimmers. Bears use shelters, such as caves and logs, as their dens; most species occupy their dens during the winter for a long period of hibernation, up to 100 days.

    Bears have been hunted since prehistoric times for their meat and fur; they have been used for bear-baiting and other forms of entertainment, such as being made to dance. With their powerful physical presence, they play a prominent role in the arts, mythology, and other cultural aspects of various human societies. In modern times, bears have come under pressure through encroachment on their habitats and illegal trade in bear parts, including the Asian bile bear market. The IUCN lists six bear species as vulnerable or endangered, and even least concern species, such as the brown bear, are at risk of extirpation in certain countries. The poaching and international trade of these most threatened populations are prohibited, but still ongoing.

    Etymology

    The English word "bear" comes from Old English bera and belongs to a family of names for the bear in Germanic languages, such as Swedish björn, also used as a first name, that originate from an adjective meaning "brown". "Bear" therefore originally meant "the brown one." This terminology for the animal originated as a taboo avoidance term: proto-Germanic tribes replaced their original word for bear – arkto – with this euphemistic expression out of fear that speaking the animal's true name might cause it to appear.[1][2]

    Bear taxon names such as Arctoidea and Helarctos come from the ancient Greek word ἄρκτος (arktos), meaning bear,[3] as do the names "arctic" and "antarctic", from the constellation Ursa Major, the "Great Bear", prominent in the northern sky.[4]

    Bear taxon names such as Ursidae and Ursus come from Latin Ursus/Ursa, he-bear/she-bear.[4] The female first name "Ursula", originally derived from a Christian saint's name, means "little she-bear" (diminutive of Latin ursa). In Switzerland, the male first name "Urs" is especially popular, while the name of the canton and city of Bern is derived from Bär, German for bear. The Germanic name Bernard (including Bernhardt and similar forms) means "bear-brave", "bear-hardy", or "bold bear".[5][6] The Old English name Beowulf is a kenning, "bee-wolf", for bear, in turn meaning a brave warrior.[7]

    Taxonomy and phylogeny

    The family Ursidae is one of nine families in the suborder Caniformia, or "doglike" carnivorans, within the order Carnivora. Bears' closest living relatives are the pinnipeds, canids, and musteloids.[8] Modern bears comprise eight species in three subfamilies: Ailuropodinae (monotypic with the giant panda), Tremarctinae (monotypic with the spectacled bear), and Ursinae (containing six species divided into one to three genera, depending on the authority). Nuclear chromosome analysis show that the karyotype of the six ursine bears is nearly identical, with each having 74 chromosomes, whereas the giant panda has 42 chromosomes and the spectacled bear 52. These smaller numbers can be explained by the fusing of some chromosomes, and the banding patterns on these match those of the ursine species, but differ from those of procyonids, which supports the inclusion of these two species in Ursidae rather than in Procyonidae, where they had been placed by some earlier authorities.[9]

    Evolution

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    Plithocyon armagnacensis skull, a member of the extinct subfamily Hemicyoninae from the Miocene

    The earliest members of Ursidae belong to the extinct subfamily Amphicynodontinae, including Parictis (late Eocene to early middle Miocene, 38–18 Mya) and the slightly younger Allocyon (early Oligocene, 34–30 Mya), both from North America. These animals looked very different from today's bears, being small and raccoon-like in overall appearance, with diets perhaps more similar to that of a badger. Parictis does not appear in Eurasia and Africa until the Miocene.[10] It is unclear whether late-Eocene ursids were also present in Eurasia, although faunal exchange across the Bering land bridge may have been possible during a major sea level low stand as early as the late Eocene (about 37 Mya) and continuing into the early Oligocene.[11] European genera morphologically very similar to Allocyon, and to the much younger American Kolponomos (about 18 Mya),[12] are known from the Oligocene, including Amphicticeps and Amphicynodon.[11] There has been various morphological evidence linking amphicynodontines with pinnipeds, as both groups were semi-aquatic, otter-like mammals.[13][14][15] In addition to the support of the pinniped–amphicynodontine clade, other morphological and some molecular evidence supports bears being the closet living relatives to pinnipeds.[16][17][18][14][19][14][15]

    The raccoon-sized, dog-like Cephalogale is the oldest-known member of the subfamily Hemicyoninae, which first appeared during the middle Oligocene in Eurasia about 30 Mya.[11] The subfamily includes the younger genera Phoberocyon (20–15 Mya), and Plithocyon (15–7 Mya). A Cephalogale-like species gave rise to the genus Ursavus during the early Oligocene (30–28 Mya); this genus proliferated into many species in Asia and is ancestral to all living bears. Species of Ursavus subsequently entered North America, together with Amphicynodon and Cephalogale, during the early Miocene (21–18 Mya). Members of the living lineages of bears diverged from Ursavus between 15 and 20 Mya,[20][21] likely via the species Ursavus elmensis. Based on genetic and morphological data, the Ailuropodinae (pandas) were the first to diverge from other living bears about 19 Mya, although no fossils of this group have been found before about 5 Mya.[22]

    The New World short-faced bears (Tremarctinae) differentiated from Ursinae following a dispersal event into North America during the mid-Miocene (about 13 Mya).[22] They invaded South America (≈1 Ma) following formation of the Isthmus of Panama.[23] Their earliest fossil representative is Plionarctos in North America (~ 10–2 Ma). This genus is probably the direct ancestor to the North American short-faced bears (genus Arctodus), the South American short-faced bears (Arctotherium), and the spectacled bears, Tremarctos, represented by both an extinct North American species (T. floridanus), and the lone surviving representative of the Tremarctinae, the South American spectacled bear (T. ornatus).[11]

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    Fossil of the cave bear (Ursus spelaeus), a relative of the brown bear and polar bear from the Pleistocene epoch in Europe

    The subfamily Ursinae experienced a dramatic proliferation of taxa about 5.3–4.5 Mya, coincident with major environmental changes; the first members of the genus Ursus appeared around this time.[22] The sloth bear is a modern survivor of one of the earliest lineages to diverge during this radiation event (5.3 Mya); it took on its peculiar morphology, related to its diet of termites and ants, no later than by the early Pleistocene. By 3–4 Mya, the species Ursus minimus appears in the fossil record of Europe; apart from its size, it was nearly identical to today's Asian black bear. It is likely ancestral to all bears within Ursinae, perhaps aside from the sloth bear. Two lineages evolved from U. minimus: the black bears (including the sun bear, the Asian black bear, and the American black bear); and the brown bears (which includes the polar bear). Modern brown bears evolved from U. minimus via Ursus etruscus, which itself is ancestral to the extinct Pleistocene cave bear. Species of Ursinae have migrated repeatedly into North America from Eurasia as early as 4 Mya during the early Pliocene.[24][25] The polar bear is the most recently evolved species and descended from the brown bear around 400,000 years ago.[26]

    Phylogeny

    The bears form a clade within the Carnivora. The red panda is not a bear but a musteloid. The cladogram is based on molecular phylogeny of six genes in Flynn, 2005.[27] .mw-parser-output table.clade{border-spacing:0;margin:0;font-size:100%;line-height:100%;border-collapse:separate;width:auto}.mw-parser-output table.clade table.clade{width:100%}.mw-parser-output table.clade td{border:0;padding:0;vertical-align:middle;text-align:center}.mw-parser-output table.clade td.clade-label{width:0.8em;border:0;padding:0 0.2em;vertical-align:bottom;text-align:center}.mw-parser-output table.clade td.clade-slabel{border:0;padding:0 0.2em;vertical-align:top;text-align:center}.mw-parser-output table.clade td.clade-bar{vertical-align:middle;text-align:left;padding:0 0.5em}.mw-parser-output table.clade td.clade-leaf{border:0;padding:0;text-align:left;vertical-align:middle}.mw-parser-output table.clade td.clade-leafR{border:0;padding:0;text-align:right}

    Carnivora  

    Feliformia Ocelot

    Caniformia

    Canidae African golden wolf

    Arctoidea

    Hemicyonidae Hemicyon sansaniensis

       

    Ursidae Brown bear

           

    Pinnipedia Common seal

    Musteloidea

    Ailuridae, inc. red panda Ailurus fulgens - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam -(white background).jpg

       

    Other musteloids Steppe polecat

               

    There are two phylogenetic hypotheses on the relationships among extant and fossil bear spcies. One is all species of bears are classified in seven subfamilies as adopted here and related articles: Amphicynodontinae, Hemicyoninae, Ursavinae, Agriotheriinae, Ailuropodinae, Tremarctinae, and Ursinae.[28][29][30][31] Below is a cladogram of the subfamilies of bears after McLellan and Reiner (1992)[28] and Qiu et a. (2014):[31]

    Ursidae

    Amphicynodontinae Kolponomos newportensis .jpg

         

    Hemicyoninae Hemicyon sansaniensis

         

    Ursavinae

         

    Agriotheriinae

         

    Ailuropodinae Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg

         

    Tremarctinae Spectacled bear (1829).jpg

       

    Ursinae Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

                 

    The second alternative phylogenetic hypothesis was implemented by McKenna et al. (1997) is to classify all the bear species into the superfamily Ursoidea, with Hemicyoninae and Agriotheriinae being classified in the family "Hemicyonidae".[32] Amphicynodontinae under this classification were classified as stem-pinnipeds in the superfamily Phocoidea.[32] In the McKenna and Bell classification both bears and pinnipeds in a parvorder of carnivoran mammals known as Ursida, along with the extinct bear dogs of the family Amphicyonidae.[32] Below is the cladogram based on McKenna and Bell (1997) classification:[32]

    Ursida    

    Amphicyonidae Daphoenodon superbus by R. B. Horsfall (coloured).png

            Phocoidea

    Amphicynodontidae Kolponomos newportensis .jpg

       

    Pinnipedia Common seal

            Ursoidea   †Hemicyonidae

    Hemicyoninae Hemicyon sansaniensis

       

    Agriotheriinae

            Ursidae

    Ursavinae

           

    Ailuropodinae Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg

           

    Tremarctinae Spectacled bear (1829).jpg

       

    Ursinae Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

                         

    The phylogeny of extant bear species is shown in a cladogram based on complete mitochondrial DNA sequences from Yu et al., 2007.[33] The giant panda, followed by the spectacled bear are clearly the oldest species. The relationships of the other species are not very well resolved, though the polar bear and the brown bear form a close grouping.[9]

    Ursidae          

    Brown bear Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

       

    Polar bear Lossy-page1-2518px-Ursus maritimus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

             

    Asian black bear Ursus thibetanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam -(white background).jpg

       

    American black bear Ursus americanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

         

    Sun bear Ursus malayanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

           

    Sloth bear Tremarctos ornatus 1824 (flipped).jpg

         

    Spectacled bear Spectacled bear (1829).jpg

         

    Giant panda Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg

       

    Classification

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    Restoration of Kolponomos a large marine bear.
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    Restoration of Hemicyon by Jay Matternes
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    Mandible of Agriotherium. This genus that existed from the Miocene to the Pleistocene is the only known ursid to have lived in sub-Saharan Africa.[34]
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    Skull of Indarctos atticus. Indarctos was a Miocene genus found across the northern hemisphere.[35]
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    Giant panda (Ailuropoda melanoleuca) eating bamboo leaves.
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    Restoration of Arctotherium, a South American Pleistocene genus from a lineage whose only survivor is the spectacled bear. It is the largest bear ever found and contender for the largest carnivorous land mammal known.[36][37]
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    A sun bear (Helarctos malayanus) sitting upright.
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    Ice age cave bear (Ursus spelaeus) from 150,000 BCE
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    A brown bear (Ursus arctos) surveying the landscape.
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    Some evidence of a bear found along a popular hiking trail in British Columbia, Canada
    • Family Ursidae (G. Fischer de Waldheim, 1817)
      • Subfamily †Amphicynodontinae (Simpson, 1945)
        • Amphicticeps (Matthew and Granger, 1924)
          • Amphicticeps makhchinus (Wang et al., 2005)
          • Amphicticeps dorog (Wang et al., 2005)
          • Amphicticeps shackelfordi (Matthew and Granger, 1924)
        • Parictis (Scott, 1893)
          • Parictis primaevus (Scott, 1893)
          • Parictis personi (Chaffee, 1954)
          • Parictis montanus (Clark & Guensburg, 1972)
          • Parictis parvus (Clark & Beerbower, 1967)
          • Parictis gilpini (Clark & Guensburg, 1972)
          • Parictis dakotensis (Clark, 1936)
        • Kolponomos (Stirton, 1960)
          • Kolponomos newportensis (Tedford et al., 1994)
          • Kolponomos clallamensis (Stirton, 1960)
        • Allocyon (Merriam, 1930)
          • Allocyon loganensis (Merriam, 1930)
        • Pachycynodon (Schlosser, 1888)
          • Pachycynodon tedfordi (Wang & Qiu, 2003)
          • Pachycynodon tenuis (Teilhard de Chardin, 1915)
          • Pachycynodon filholi (Schlosser, 1888)
          • Pachycynodon boriei (Filhol, 1876)
          • Pachycynodon crassirostris (Schlosser, 1888)
        • Amphicynodon (Filhol, 1881)
          • Amphicynodon mongoliensis (Janovskaja, 1970)
          • Amphicynodon teilhardi (Matthew and Granger, 1924)
          • Amphicynodon typicus (Schlosser, 1888)
          • Amphicynodon chardini (Cirot and De Bonis, 1992)
          • Amphicynodon cephalogalinus (Teilhard, 1915)
          • Amphicynodon gracilis (Filhol, 1874)
          • Amphicynodon crassirostris (Filhol, 1876)
          • Amphicynodon brachyrostris (Filhol, 1876)
          • Amphicynodon leptorhynchus (Filhol, 1874)
          • Amphicynodon velaunus (Aymard, 1846)
      • Subfamily †Hemicyoninae (Frick, 1926)
        • Tribe †Cephalogalini (de Bonis, 2013)
          • Adelpharctos (de Bonis, 1971)
            • Adelpharctos ginsburgi (de Bonis, 2011)
            • Adelpharctos mirus (de Bonis, 1971)
          • Cyonarctos (de Bonis, 2013)
            • Cyonarctos dessei (de Bonis, 2013)
          • Phoberogale (Ginsburg & Morales, 1995)
            • Phoberogale minor (Filhol, 1877)
            • Phoberogale bonali (Helbing, 1928)
            • Phoberogale depereti (Viret, 1929)
            • Phoberogale gracile (Pomel, 1847)
          • Filholictis (de Bonis, 2013)
            • Filholictis filholi (Munier-Chalmas, 1877)
          • Cephalogale (Jourdan, 1862)
            • Cephalogale shareri (Wang, et al., 2009)
            • Cephalogale gergoviensis (Viret, 1929)
            • Cephalogale ginesticus (Kuss, 1962)
            • Cephalogale geoffroyi (Jourdan, 1862)
        • Tribe †Phoberocyonini (Ginsburg & Morales, 1995)
          • Plithocyon (Ginsburg, 1955)
            • Plithocyon armagnacensis (Ginsburg, 1955)
            • Plithocyon statzlingii (Frick, 1926)
            • Plithocyon bruneti (Ginsburg, 1980)
            • Plithocyon barstowensis (Frick, 1926)
            • Plithocyon ursinus (Cope, 1875)
          • Phoberocyon (Ginsburg, 1955)
            • Phoberocyon hispanicus (Ginsburg & Morales, 1998)
            • Phoberocyon dehmi (Ginsburg, 1955)
            • Phoberocyon huerzeleri (Ginsburg, 1955)
            • Phoberocyon aurelianensis (Mayet, 1908)
            • Phoberocyon youngi (Xiang et al., 1986)
            • Phoberocyon johnhenryi (White, 1947)
        • Tribe †Hemicyonini (Frick, 1926)
          • Zaragocyon (Ginsburg & Morales, 1995)
            • Zaragocyon daamsi (Ginsburg & Morales, 1995)
          • Dinocyon (Jourdan, 1861)
            • Dinocyon aurelianensis (Frick, 1926)
            • Dinocyon sansaniensis (Frick, 1926)
            • Dinocyon thenardi (Jourdan, 1861)
          • Hemicyon (Lartet, 1851)
            • Hemicyon barbouri (Colbert, 1941)
            • Hemicyon teilhardi (Colbert, 1939)
            • Hemicyon grivensis (Frick, 1926)
            • Hemicyon minor (Dépéret, 1887)
            • Hemicyon sansaniensis (Lartet, 1851)
      • Subfamily †Ursavinae (Hendey, 1980)
        • Ballusia (Ginsburg & Morales, 1998)
          • Ballusia elmensis (Stehlin, 1917)
          • Ballusia hareni (Ginsburg, 1989)
          • Ballusia orientalis (Qiu et al., 1985)
        • Ursavus (Schlosser, 1899)
          • Ursavus brevirhinus (Hofmann, 1887)
          • Ursavus primaevus (Gaillard, 1899)
          • Ursavus intermedius (Koenigswald, 1925)
          • Ursavus pawniensis (Frick, 1926)
          • Ursavus ehrenbergi (Brunner, 1942)
          • Ursavus sylvestris (Qiu & Qi, 1990)
          • Ursavus isorei (Ginsburg & Morales, 1998)
          • Ursavus tedfordi (Zhanxiang et al., 2014)
      • Subfamily †Agriotheriinae (Kretzoi, 1929)
        • Agriotherium (Wagner, 1837)
          • Agriotherium myanmarensis (Ogino et al., 2011)
          • Agriotherium insigne (Gervais, 1859)
          • Agriotherium inexpetans (Qiu et al., 1991)
          • Agriotherium palaeindicus (Lydekker, 1878)
          • Agriotherium sivalensis (Falconer & Cautley, 1836)
          • Agriotherium africanum (Hendey, 1972)
          • Agriotherium coffeyi (Dalquest, 1986)
          • Agriotherium gregoryi (Frick, 1926)
          • Agriotherium schneideri (Sellards, 1916)
      • Subfamily Ailuropodinae (Grevé, 1894)[38]
        • Tribe †Indarctini (Abella et al., 2012)
          • Miomaci (de Bonis et al., 2017)
            • Miomaci pannonicum (de Bonis et al., 2017)
          • Indarctos (Pilgrim, 1913)
            • Indarctos punjabensis (Lydekker, 1884)
            • Indarctos zdanskyi (Qiu & Tedford, 2003)[39]
            • Indarctos sinensis (Zdansky, 1924)
            • Indarctos vireti (Villalta & Crusafont, 1943)
            • Indarctos arctoides (Deperet, 1895)
            • Indarctos anthracitis (Weithofer, 1888)
            • Indarctos salmontanus (Pilgrim, 1913)
            • Indarctos atticus (Weithofer, 1888)
            • Indarctos bakalovi (Kovachev, 1988)
            • Indarctos lagrelli (Zdansky, 1924)
            • Indarctos oregonensis (Merriam et al., 1916)
            • Indarctos nevadensis (Macdonald, 1959)[40]
        • Tribe Ailuropodini (Grevé, 1894)
      • Subfamily Tremarctinae (Merriam & Stock, 1925)[41]
        • Plionarctos (Frick, 1926)
          • Plionarctos harroldorum (Tedfored & Martin, 2001)
          • Plionarctos edensis (Frick, 1926)
        • Arctodus (Leidy, 1854)
          • Arctodus simus (Cope, 1879)
          • Arctodus pristinus (Leidy, 1854)
        • Arctotherium (Burmeister, 1879)
          • Arctotherium angustidens (Gervais & Ameghino, 1880)
          • Arctotherium vetustum (Ameghino, 1885)
          • Arctotherium wingei (Ameghino, 1902)
          • Arctotherium bonariense (Gervais, 1852)
          • Arctotherium tarijense (Ameghino, 1902)
        • Tremarctos (Gervais, 1855)
      • Subfamily Ursinae (G. Fischer de Waldheim, 1817)

    Physical characteristics

    Size

    @media all and (max-width:720px){.mw-parser-output .tmulti>.thumbinner{width:100%!important;max-width:none!important}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:none!important;width:100%!important;text-align:center}}
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    Polar bear (left) and sun bear, the largest and smallest species respectively, on average.

    The bear family includes the most massive extant terrestrial members of the order Carnivora.[a] The polar bear is considered to be the largest extant species,[43] with adult males weighing 350–700 kg (772–1,543 lb) and measuring 2.4–3 metres (7 ft 10 in–9 ft 10 in) in total length.[44] The smallest species is the sun bear, which ranges 25–65 kg (55–143 lb) in weight and 100–140 cm (39–55 in) in length.[45] Prehistoric North and South American short-faced bears were the largest species known to have lived. The latter estimated to have weighed 1,600 kg (3,500 lb) and stood 3.4 m (11 ft) tall.[37][36] Body weight varies throughout the year in bears of temperate and arctic climates, as they build up fat reserves in the summer and autumn and lose weight during the winter.[46]

    Morphology

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    Unlike most other Carnivora, bears have plantigrade feet. Drawing by Richard Owen, 1866.

    Bears are generally bulky and robust animals with short tails. They are sexually dimorphic with regard to size, with males typically being larger.[47][48] Larger species tend to show increased levels of sexual dimorphism in comparison to smaller species.[48] Relying as they do on strength rather than speed, bears have relatively short limbs with thick bones to support their bulk. The shoulder blades and the pelvis are correspondingly massive. The limbs are much straighter than those of the big cats as there is no need for them to flex in the same way due to the differences in their gait. The strong forelimbs are used to catch prey, to excavate dens, to dig out burrowing animals, to turn over rocks and logs to locate prey, and to club large creatures.[46]

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    Despite being quadrupeds, bears can stand and sit as humans do

    Unlike most other land carnivorans, bears are plantigrade. They distribute their weight toward the hind feet, which makes them look lumbering when they walk. They are capable of bursts of speed but soon tire, and as a result mostly rely on ambush rather than the chase. Bears can stand on their hind feet and sit up straight with remarkable balance. Their front paws are flexible enough to grasp fruit and leaves. Bears' non-retractable claws are used for digging, climbing, tearing, and catching prey. The claws on the front feet are larger than those on the back and may be a hindrance when climbing trees; black bears are the most arboreal of the bears, and have the shortest claws. Pandas are unique in having a bony extension on the wrist of the front feet which acts as a thumb, and is used for gripping bamboo shoots as the animals feed.[46]

    Most mammals have agouti hair, with each individual hair shaft having bands of colour corresponding to two different types of melanin pigment. Bears however have a single type of melanin and the hairs have a single colour throughout their length, apart from the tip which is sometimes a different shade. The coat consists of long guard hairs, which form a protective shaggy covering, and short dense hairs which form an insulating layer trapping air close to the skin. The shaggy coat helps maintain body heat during winter hibernation and is shed in the spring leaving a shorter summer coat. Polar bears have hollow, translucent guard hairs which gain heat from the sun and conduct it to the dark-coloured skin below. They have a thick layer of blubber for extra insulation, and the soles of their feet have a dense pad of fur.[46] Other than the bold black-and-white pelage of the panda, bears tend to be uniform in colour, although some species may have markings on the chest or face.[49]

    Bears have small rounded ears so as to minimise heat loss, but neither their hearing or sight are particularly acute. Unlike many other carnivorans they have colour vision, perhaps to help them distinguish ripe nuts and fruits. They are unique among carnivorans in not having touch-sensitive whiskers on the muzzle; however, they have an excellent sense of smell, better than that of the dog, or possibly any other mammal. They use smell for signalling to each other (either to warn off rivals or detect mates) and for finding food. Smell is the principal sense used by bears to locate most of their food, and they have excellent memories which helps them to relocate places where they have found food before.[46]

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    Brown bear skull

    The skulls of bears are massive, providing anchorage for the powerful masseter and temporal jaw muscles. The canine teeth are large but mostly used for display, and the molar teeth flat and crushing. Unlike most other members of the Carnivora, bears have relatively undeveloped carnassial teeth, and their teeth are adapted for a diet that includes a significant amount of vegetable matter.[46] Considerable variation occurs in dental formula even within a given species. This may indicate bears are still in the process of evolving from a mainly meat-eating diet to a predominantly herbivorous one. Polar bears appear to have secondarily re-evolved carnassial-like cheek teeth, as their diets have switched back towards carnivory.[50] Sloth bears lack lower central incisors and use their protusible lips for sucking up the termites on which they feed.[46] The general dental formula for living bears is: 3.1.2–4.23.1.2–4.3.[46] The structure of the larynx of bears appears to be the most basal of the caniforms.[51] They possess air pouches connected to the pharynx which may amplify their vocalisations.[52]

    Bears have a fairly simple digestive system typical for carnivorans, with a single stomach, short undifferentiated intestines and no cecum.[53][54] Even the herbivorous giant panda still has the digestive system of a carnivore, as well as carnivore-specific genes. Its ability to digest cellulose is ascribed to the microbes in its gut.[55] Bears must spend much of their time feeding in order to gain enough nutrition from foliage. The panda, in particular, spends 12–15 hours a day feeding.[56]

    Distribution and habitat

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    The spectacled bear is the only species found in South America[57]
    Further information: List of carnivorans by population

    Extant bears are found in sixty countries primarily in the Northern Hemisphere and are concentrated in Asia, North America, and Europe. An exception is the spectacled bear; native to South America, it inhabits the Andean region.[57] The sun bear's range extends below the equator in Southeast Asia.[58] The Atlas bear, a subspecies of the brown bear was distributed in North Africa from Morocco to Libya, but it became extinct around the 1870s.[59]

    The most widespread species is the brown bear, which occurs from Western Europe eastwards through Asia to the western areas of North America. The American black bear is restricted to North America, and the polar bear is restricted to the Arctic Sea. All the remaining species of bear are Asian.[57] They occur in a range of habitats which include tropical lowland rainforest, both coniferous and broadleaf forests, prairies, steppes, montane grassland, alpine scree slopes, Arctic tundra and in the case of the polar bear, ice floes.[57][60] Bears may dig their dens in hillsides or use caves, hollow logs and dense vegetation for shelter.[60]

    Behaviour and life history

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    American black bear tracks at Superior National Forest, Minnesota, the United States of America

    Brown and American black bears are generally diurnal, meaning that they are active for the most part during the day, though they may forage substantially by night.[61] Other species may be nocturnal, active at night, though female sloth bears with cubs may feed more at daytime to avoid competition from conspecifics and nocturnal predators.[62] Bears are overwhelmingly solitary and are considered to be the most asocial of all the Carnivora. The only times bears are encountered in small groups are mothers with young or occasional seasonal bounties of rich food (such as salmon runs).[63][64] Fights between males can occur and older individuals may have extensive scarring, which suggests that maintaining dominance can be intense.[65] With their acute sense of smell, bears can locate carcasses from several kilometres away. They use olfaction to locate other foods, encounter mates, avoid rivals and recognise their cubs.[46]

    Feeding

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    Most bears are opportunistic omnivores and consume more plant than animal matter. They eat anything from leaves, roots, and berries to insects, carrion, fresh meat, and fish, and have digestive systems and teeth adapted to such a diet.[57] At the extremes are the almost entirely herbivorous giant panda and the mostly carnivorous polar bear. However, all bears feed on any food source that becomes seasonally available.[56] For example, Asiatic black bears in Taiwan consume large numbers of acorns when these are most common, and switch to ungulates at other times of the year.[66]

    When foraging for plants, bears choose to eat them at the stage when they are at their most nutritious and digestible, typically avoiding older grasses, sedges and leaves.[54][56] Hence, in more northern temperate areas, browsing and grazing is more common early in spring and later becomes more restricted.[67] Knowing when plants are ripe for eating is a learned behaviour.[56] Berries may be foraged in bushes or at the tops of trees, and bears try to maximize the number of berries consumed versus foliage.[67] In autumn, some bear species forage large amounts of naturally fermented fruits, which affects their behaviour.[68] Smaller bears climb trees to obtain mast (edible reproductive parts, such as acorns).[69] Such masts can be very important to the diets of these species, and mast failures may result in long-range movements by bears looking for alternative food sources.[70] Brown bears, with their powerful digging abilities, commonly eat roots.[67] The panda's diet is over 99% bamboo,[71] of 30 different species. Its strong jaws are adapted for crushing the tough stems of these plants, though they prefer to eat the more nutritious leaves.[72][73] Bromeliads can make up to 50% of the diet of the spectacled bear, which also has strong jaws to bite them open.[74]

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    Brown bear feeding on infrequent, but predictable, salmon migrations in Alaska

    The sloth bear, though not as specialised as polar bears and the panda, has lost several front teeth usually seen in bears, and developed a long, suctioning tongue to feed on the ants, termites, and other burrowing insects they favour. At certain times of the year, these insects can make up 90% of their diets.[75] Some species may raid the nests of wasps and bees for the honey and immature insects, in spite of stinging from the adults.[76] Sun bears use their long tongues to lick up both insects and honey.[77] Fish are an important source of food for some species, and brown bears in particular gather in large numbers at salmon runs. Typically, a bear plunges into the water and seizes a fish with its jaws or front paws. The preferred parts to eat are the brain and eggs. Small burrowing mammals like rodents may be dug out and eaten.[78][67]

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    Polar bear feeding on a seal on an ice floe north of Svalbard, Norway. It is the most carnivorous species.

    The brown bear and both species of black bears sometimes take large ungulates, such as deer and bovids, mostly the young and weak.[66][79][78] These animals may be taken by a short rush and ambush, though hiding young may be stiffed out and pounced on.[67][80] The polar bear mainly preys on seals, stalking them from the ice or breaking into their dens. They primarily eat the highly digestible blubber.[81][78] Large mammalian prey is typically killed by a bite to the head or neck, or (in the case of young) simply pinned down and mauled.[67][82] Predatory behaviour in bears is typically taught to the young by the mother.[78]

    Bears are prolific scavengers and kleptoparasites, stealing food caches from rodents, and carcasses from other predators.[54][83] For hibernating species, weight gain is important as it provides nourishment during winter dormancy. A brown bear can eat 41 kg (90 lb) of food and gain 2–3 kg (4.4–6.6 lb) of fat a day prior to entering its den.[84]

    Communication

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    Captive Asian black bears during an aggressive encounter

    Bears produce a number of vocal and non-vocal sounds. Tongue-clicking, grunting or chuffing many be made in cordial situations, such as between mothers and cubs or courting couples, while moaning, huffing, sorting or blowing air is made when an individual is stressed. Barking is produced during times of alarm, excitement or to give away the animal's position. Warning sounds include jaw-clicking and lip-popping, while teeth-chatters, bellows, growls, roars and pulsing sounds are made in aggressive encounters. Cubs may squeal, bawl, bleat or scream when in distress and make motor-like humming when comfortable or nursing.[51][85][86][87][88][89]

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    Sloth bear rubbing against tree at Nagarhole Tiger Reserve, India

    Bears sometimes communicate with visual displays such as standing upright, which exaggerates the individual's size. The chest markings of some species may add to this intimidating display. Staring is an aggressive act and the facial markings of spectacled bears and giant pandas may help draw attention to the eyes during agonistic encounters.[49] Individuals may approach each other by stiff-legged walking with the head lowered. Dominance between bears is asserted by making a frontal orientation, showing the canine teeth, muzzle twisting and neck stretching. A subordinate may respond with a lateral orientation, by turning away and dropping the head and by sitting or lying down.[64][90]

    Bears may mark territory by rubbing against trees and other objects which may serve to spread their scent. This is usually accompanied by clawing and biting the object. Bark may be spread around to draw attention to the marking post.[91] Pandas are known to mark objects with urine and a waxy substance from their anal glands.[92] Polar bears leave behind their scent in their tracks which allow individuals to keep track of one another in the vast Arctic wilderness.[93]

    Reproduction and development

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    American black bears mating at the North American Bear Center

    The mating system of bears has variously been described as a form of polygyny, promiscuity and serial monogamy.[94][95][96] During the breeding season, males take notice of females in their vicinity and females become more tolerant of males. A male bear may visit a female continuously over a period of several days or weeks, depending on the species, to test her reproductive state. During this time period, males try to prevent rivals from interacting with their mate. Courtship may be brief, although in some Asian species, courting pairs may engage in wrestling, hugging, mock fighting and vocalising. Ovulation is induced by mating, which can last up to 30 minutes depending on the species.[95]

    Polar bear mother nursing her cub

    Gestation typically lasts 6–9 months, including delayed implantation, and litter size numbers up to four cubs.[97] Giant pandas may give birth to twins but they can only suckle one young and the other is left to die.[98] In northern living species, birth takes place during winter dormancy. Cubs are born blind and helpless with at most a thin layer of hair, relying on their mother for warmth. The milk of the female bear is rich in fat and antibodies and cubs may suckle for up to a year after they are born. By 2–3 months, cubs can follow their mother outside the den. They usually follow her on foot, but sloth bear cubs may ride on their mother's back.[97][60] Male bears play no role in raising young. Infanticide, where an adult male kills the cubs of another, has been recorded in polar bears, brown bears and American black bears but not in other species.[99] Males kill young to bring the female into oestrus.[100] Cubs may flee and the mother defends them even at the cost of her life.[101][102][103]

    In some species, offspring may become independent around the next spring, through some may stay until the female successfully mates again. Bears reach sexual maturity shortly after they disperse; at around 3–6 years depending on the species. Male Alaskan brown bears and polar bears may continue to grow until they are 11 years old.[97] Lifespan may also vary between species. The brown bear can live an average of 25 years.[104]

    Hibernation

    Main article: Hibernation

    Bears of northern regions, including the American black bear and the grizzly bear, hibernate in the winter.[105][106] During hibernation, the bear's metabolism slows down, its body temperature decreases slightly, and its heart rate slows from a normal value of 55 to just 9 beats per minute.[107] Bears normally do not wake during their hibernation, and can go the entire period without eating, drinking, urinating, or defecating.[46] A fecal plug is formed in the colon, and is expelled when the bear wakes in the spring.[108] If they have stored enough body fat, their muscles remain in good condition, and their protein maintenance requirements are met from recycling waste urea.[46] Female bears give birth during the hibernation period, and are roused when doing so.[106]

    Predators, parasites and pathogens

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    Hunters with shot bear, Sweden, early 20th century. This photograph is in the Nordic Museum.

    Bears do not have many predators. The most important are humans, and as they started cultivating crops, they increasingly came in conflict with the bears that raided them. Since the invention of firearms, people have been able to kill bears with greater ease.[109] Felids like the tiger may also prey on bears,[110][111] particularly cubs, which may be also be threatened by canids.[9][96]

    Bears are parasitized by eighty species of parasites, including single-celled protozoans and gastro-intestinal worms, and nematodes and flukes in their heart, liver, lungs and bloodstream. Externally they have ticks, fleas and lice. A study of American black bears found seventeen species of endoparasite including the protozoan Sarcocystis, the parasitic worm Diphyllobothrium mansonoides, and the nematodes Dirofilaria immitis, Capillaria aerophila, Physaloptera sp., Strongyloides sp. and others. Of these, D. mansonoides and adult C. aerophila were causing pathological symptoms.[112] By contrast, polar bears have few parasites; many parasitic species need a secondary, usually terrestrial, host, and the polar bear's life style is such that few alternative hosts exist in their environment. The protozoan Toxoplasma gondii has been found in polar bears, and the nematode Trichinella nativa can cause a serious infection and decline in older polar bears.[113] Bears in North America are sometimes infected by a Morbillivirus similar to the canine distemper virus.[114] They are susceptible to infectious canine hepatitis (CAV-1), with free-living black bears dying rapidly of encephalitis and hepatitis.[115]

    Relationship with humans

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    A barrel trap in Grand Teton National Park, Wyoming used to relocate bears away from where they might attack humans

    Conservation

    Main article: Bear conservation

    In modern times, bears have come under pressure through encroachment on their habitats[116] and illegal trade in bear parts, including the Asian bile bear market, though hunting is now banned, largely replaced by farming.[117] The IUCN lists six bear species as vulnerable;[118] even the two least concern species, the brown bear and the American black bear,[118] are at risk of extirpation in certain areas. In general these two species inhabit remote areas with little interaction with humans, and the main non-natural causes of mortality are hunting, trapping, road-kill and depredation.[119]

    Laws have been passed in many areas of the world to protect bears from habitat destruction. Public perception of bears is often positive, as people identify with bears due to their omnivorous diets, their ability to stand on two legs, and their symbolic importance.[120] Support for bear protection is widespread, at least in more affluent societies.[121] Where bears raid crops or attack livestock, they may come into conflict with humans.[122][123] In poorer rural regions, attitudes may be more shaped by the dangers posed by bears, and the economic costs they cause to farmers and ranchers.[122]

    Attacks

    Main article: Bear attacks

    Several bear species are dangerous to humans, especially in areas where they have become used to people; elsewhere, they generally avoid humans. Injuries caused by bears are rare, but are widely reported.[124] Bears may attack humans in response to being startled, in defense of young or food, or even for predatory reasons.[125]

    Entertainment, hunting, food and folk medicine

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    The dancing bear by William Frederick Witherington, 1822

    Bears in captivity have for centuries been used for entertainment. They have been trained to dance,[126] and were kept for baiting in Europe at least since the 16th century. There were five bear-baiting gardens in Southwark, London at that time; archaeological remains of three of these have survived.[127] Across Europe, nomadic Romani bear handlers called Ursari lived by busking with their bears from the 12th century.[128]

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    A nomadic ursar, a Romani bear-busker. Drawing by Theodor Aman, 1888

    Bears have been hunted for sport, food, and folk medicine. Their meat is dark and stringy, like a tough cut of beef. In Cantonese cuisine, bear paws are considered a delicacy. Bear meat should be cooked thoroughly, as it can be infected with the parasite Trichinella spiralis.[129][130]

    The peoples of eastern Asia use bears' body parts and secretions (notably their gallbladders and bile) as part of traditional Chinese medicine. More than 12,000 bears are thought to be kept on farms in China, Vietnam, and South Korea for the production of bile. Trade in bear products is prohibited under CITES, but bear bile has been detected in shampoos, wine and herbal medicines sold in Canada, the United States and Australia.[131]

    Literature, art and symbolism

    Further information: Bear worship, Jean de l'Ours, Berserker, and Kalevala
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    Onikuma, a Japanese demon bear from Ehon Hyaku Monogatari, c. 1841
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    The Latvian legendary hero Lāčplēsis kills a bear with his bare hands

    There is evidence of prehistoric bear worship, though this is disputed by archaeologists.[132] The prehistoric Finns,[133] Siberian peoples[134] and more recently Koreans considered the bear as the spirit of their forefathers.[135] There is evidence of bear worship in early Chinese and Ainu cultures.[136] In many Native American cultures, the bear is a symbol of rebirth because of its hibernation and re-emergence.[137] The image of the mother bear was prevalent throughout societies in North America and Eurasia, based on the female's devotion and protection of her cubs.[138] Japanese folklore features the Onikuma, a "demon bear" that walks upright.[139] The Ainu of northern Japan, a different people from the Japanese, saw the bear instead as sacred; Hirasawa Byozan painted a scene in documentary style of a bear sacrifice in an Ainu temple, complete with offerings to the dead animal's spirit.[140]

    In Korean mythology, a tiger and a bear prayed to Hwanung, the son of the Lord of Heaven, that they might become human. Upon hearing their prayers, Hwanung gave them 20 cloves of garlic and a bundle of mugwort, ordering them to eat only this sacred food and remain out of the sunlight for 100 days. The tiger gave up after about twenty days and left the cave. However, the bear persevered and was transformed into a woman. The bear and the tiger are said to represent two tribes that sought the favor of the heavenly prince.[141] The bear-woman (Ungnyeo; 웅녀/熊女) was grateful and made offerings to Hwanung. However, she lacked a husband, and soon became sad and prayed beneath a "divine birch" tree (Hangul: 신단수; Hanja: 神檀樹; RR: shindansu) to be blessed with a child. Hwanung, moved by her prayers, took her for his wife and soon she gave birth to a son named Dangun Wanggeom – who was the legendary founder of Gojoseon, the first ever Korean kingdom.[142]

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    The constellation of Ursa Major as depicted in Urania's Mirror, c. 1825

    Artio (Dea Artio in the Gallo-Roman religion) was a Celtic bear goddess. Evidence of her worship has notably been found at Bern, itself named for the bear. Her name is derived from the Celtic word for "bear", artos.[143] In ancient Greece, archaic cult of Artemis in bear form survived into Classical times at Brauron, where young Athenian girls passed an initiation right as arktai "she bears".[144] For Artemis and one of her nymphs as a she-bear, see the myth of Callisto.

    The constellations of Ursa Major and Ursa Minor, the great and little bears, are named for their supposed resemblance to bears, from the time of Ptolemy.[b][4] The nearby star Arcturus means "guardian of the bear", as if it were watching the two constellations.[146] Ursa Major has been associated with a bear for as much as 13,000 years since Paleolithic times, in the widespread Cosmic Hunt myths. These are found on both sides of the Bering land bridge, which was lost to the sea some 11,000 years ago.[147]

    Pliny the Elder's Natural History (1st century AD) claims that "when first born, [bears] are shapeless masses of white flesh, a little larger than mice; their claws alone being prominent. The mother then licks them gradually into proper shape."[148] This belief was echoed by authors of bestiaries throughout the medieval period.[149]

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    "The Three Bears", Arthur Rackham's illustration to English Fairy Tales, by Flora Annie Steel, 1918

    Bears are mentioned in the Bible; the Second Book of Kings relates the story of the prophet Elisha calling on them to eat the youths who taunted him.[150] Legends of saints taming bears are common in the Alpine zone. In the arms of the bishopric of Freising, the bear is the dangerous totem animal tamed by St. Corbinian and made to carry his civilised baggage over the mountains. Bears similarly feature in the legends of St. Romedius, Saint Gall and Saint Columbanus. This recurrent motif was used by the Church as a symbol of the victory of Christianity over paganism.[151] In the Norse settlements of northern England during the 10th century, a type of "hogback" grave cover of a long narrow block of stone, with a shaped apex like the roof beam of a long house, is carved with a muzzled, thus Christianised, bear clasping each gable end, as in the church at Brompton, North Yorkshire and across the British Isles.[152]

    Lāčplēsis, meaning "Bear-slayer", is a Latvian legendary hero who is said to have killed a bear by ripping its jaws apart with his bare hands. However, as revealed in the end of the long epic describing his life, Lāčplēsis' own mother had been a she-bear, and his superhuman strength resided in his bear ears. The modern Latvian military award Order of Lāčplēsis, called for the hero, is also known as The Order of the Bear-Slayer.

    Bears are popular in children's stories, including Winnie the Pooh,[153] Paddington Bear,[154] Gentle Ben[155] and "The Brown Bear of Norway".[156] An early version of "Goldilocks and the Three Bears",[157] was published as "The Three Bears" in 1837 by Robert Southey, many times retold, and illustrated in 1918 by Arthur Rackham.[158] The cartoon character Yogi Bear has appeared in numerous comic books, animated television shows and films.[159][160] The Care Bears began as greeting cards in 1982, and were featured as toys, on clothing and in film.[161] Around the world, many children—and some adults—have teddy bears, stuffed toys in the form of bears, named after the American statesman Theodore Roosevelt when in 1902 he had refused to shoot an American black bear tied to a tree.[162]

    Bears, like other animals, may symbolize nations. In 1911, the British satirical magazine Punch published a cartoon about the Anglo-Russian Entente by Leonard Raven-Hill in which the British lion watches as the Russian bear sits on the tail of the Persian cat.[163] The Russian Bear has been a common national personification for Russia from the 16th century onwards.[164] Smokey Bear has become a part of American culture since his introduction in 1944, with his message "Only you can prevent forest fires".[165] In the United Kingdom, the bear and staff feature on the heraldic arms of the county of Warwickshire.[166] Bears appear in the canting arms of two cities, Bern and Berlin.[167]

    Organizations

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    Juvenile pandas at the Chengdu Research Base of Giant Panda Breeding

    The International Association for Bear Research & Management, also known as the International Bear Association, and the Bear Specialist Group of the Species Survival Commission, a part of the International Union for Conservation of Nature focus on the natural history, management, and conservation of bears. Bear Trust International works for wild bears and other wildlife through four core program initiatives, namely Conservation Education, Wild Bear Research, Wild Bear Management, and Habitat Conservation.[168]

    Specialty organizations for each of the eight species of bears worldwide include:

    • Vital Ground, for the brown bear[169]
    • Moon Bears, for the Asiatic black bear[170]
    • Black Bear Conservation Coalition, for the North American black bear[171]
    • Polar Bears International, for the polar bear[172]
    • Bornean Sun Bear Conservation Centre, for the sun bear[173]
    • Wildlife SOS, for the sloth bear[174]
    • Andean Bear Conservation Project, for the Andean bear[175]
    • Chengdu Research Base of Giant Panda Breeding, for the giant panda[176]

    See also

    Notes

    1. ^ Treating pinnipeds[42] as marine mammals
    2. ^ Ptolemy named the constellations in Greek, Ἄρκτος μεγάλη (Arktos Megale) and Ἄρκτος μικρά (Arktos Mikra), the great and little bears.[145]

    References

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    Bibliography

    Comprehensive Description
    provided by Animal Diversity Web

    Bears are a small group of mostly large mammals, with 8 species in 5 genera (Ursus, Tremarctos, Melursus, Helarctos, and Ailuropoda). Although Ursidae is not diverse, species in this family are widespread and culturally significant to human populations throughout their range.

    Comprehensive Description
    provided by EOL authors

    Taxonomy and Systematics

    The bear family (Ursidae) includes just eight extant species, which are often divided into three subfamilies:

    (1) Ailuropodinae (including only the Giant Panda, Ailuropoda melanoleuca)

    (2) Tremarctinae (including only the Andean or Spectacled Bear, Tremarctos ornatus)

    (3) Ursinae or "typical bears" (including the remaining six species).

    Garshelis (2009) placed the six ursines in three genera, four in the genus Ursus (Asiatic Black Bear, U. thibetanus; American Black Bear, U. americanus; Brown Bear [generally known as Grizzly Bear where it occurs in North America], U. arctos; and Polar Bear, U. maritimus) and one each in Helarctos (Sun Bear, H. malayanus) and Melursus (Sloth Bear, M. ursinus). He noted, however, that generic placements have varied considerably over the past several decades, ranging from placing each species in its own genus (including only the Brown Bear in Ursus) to placing all bears except for the Giant Panda and Andean Bear in the genus Ursus. When each species was assigned to its own genus, the Polar Bear was placed in the genus Thalarctos, the American Black Bear in Euarctos, and the Asiatic Black Bear in Selenarctos.

    Recent molecular phylogenetic analyses indicate that, within Ursinae, one or both of the Sun Bear and Sloth Bear fall within the Ursus clade, suggesting they should not be placed in separate genera, but these same analyses do support the placement of the Giant Panda as basal to the other bears and the Spectacled Bear as basal to a clade including all six ursine species (Agnarsson et al. 2010; Nyakatura and Bininda-Emonds 2012 and references therein). Thus, molecular results are consistent with the recognition of the three ursid subfamilies originally erected on the basis of morphology and chromosome studies (ursines have 74 chromosome pairs, Andean Bears have 52 pairs, and Giant Pandas have 42 pairs; the chromosomes are mainly acrocentric in ursines, but mostly bi-armed in Giant Panda and Spectacled Bear).

    General Ecology

    All bear species, with the exception of the Polar Bear, are primarily forest-dwellers, although they do occupy other types of habitats, including scrub, tundra, and alpine areas above treeline. Bears are not common in deserts, although Andean Bears can be found in very dry areas at low elevations along the western slope of the Peruvian Andes, American Black Bears occur in semi-desert habitats in the southwestern United States and Mexico, and Asiatic Black Bears can be found in Baluchistan, an arid thorn brush region of southern Pakistan and Iran. Brown Bears can exist in even more arid conditions and an isolated remnant population persists even in the Gobi Desert of southwestern Mongolia, where the bears cluster around a few scattered oases that are slowly drying up. Bears are known from Africa only as fossils.

    All bears exhibit sexual dimorphism in size (with males being larger). This is particularly evident among the largest Brown Bears and Polar Bears, which exhibit sexual size dimorphism exceeded among mammals only by some seals and sea lions. Bears tend to be solitary; they are probably the least social carnivores.

    Bears have an extraordinarily well developed sense of smell, apparently more sensitive than that of a dog and several thousand times more sensitive than that of a human.

    The food habits of bears are diverse. Polar Bears and Giant Pandas are narrow specialists, feeding almost entirely on seals and bamboo, respectively; the other six bears are omnivorous (feeding on meat, insects, foliage, roots, nuts, berries, etc.), although the Sloth Bear feeds largely on ants and termites. Giant Pandas spend around twelve hours each day collecting and eating bamboo; much of it passes through their gut undigested, so they must consume 9 to 18 kg each day. All bears have large, stout canines used in fighting with other individuals as well as for defense from predators and for acquiring food (e.g., for feeding on seals for Polar Bears, salmon and burrowing rodents for Brown Bears, and ungulates for Brown and Black Bears, and for chewing into insect-harboring wood for Black Bears and Sun Bears). Bears feasting on salmon have been shown to move significant amounts of nitrogen to surrounding terrestrial habitats when they defecate.

    The Eight Living Bears

    Giant Panda: Giant Pandas once lived in lowland areas of eastern China, but were driven out by habitat loss resulting from human occupation. Today, they occur only in montane forests with dense stands of bamboo at 1200 to 4100 meters (more typically, 1500 to 3000 meters)—remnant areas that could not be farmed. Although at one time the taxonomic placement of the Giant Panda was controversial, in part due to morphological similarities to another bamboo-eater , the "Red Panda" (which is now placed in a family of its own and is no longer believed to be closely related to the Giant Panda), its placement in the bear family is now well established. Giant Pandas have the largest molars of all bears, which they use for crushing and grinding bamboo. Relative to skull size, Giant Pandas have the smallest canines of all bears.

    Andean Bear: Andean Bears live in South America on both the eastern and western slopes of the Andes, occurring in high elevation humid cloud forests and tussock grasslands as well as thorn, forest, and scrub desert at lower elevations. They spend much of their time in trees and feed on plants (especially terrestrial bromeliads), fruit, insects, and meat. They are apparently primarily diurnal.

    Sun Bear: Sun Bears, the smallest of the bears (adult females are typically less than 45 kg and males less than 65 kg), use their remarkably long tongues to reach into crevices for honey and insects such as stingless bees. These tropical bears are the most agile climbers of all bears, often feeding and even sleeping in trees. Both the common and scientific names of this bear are derived from the yellowish (and highly variable) patch of fur on the chest. Sun Bears are believed to be generally diurnal, except when living in areas with human activity. Much of their foraging is in fruit trees, sliding quickly down the trunk when disturbed (like all bears, they descend from trees tail first). They sometimes sleep in trees, but generally only in areas with human activity; otherwise, they are likely to sleep on the ground, often in tree cavities or under fallen trees.

    American Black Bear: American Black Bears can be found from the subarctic to the tropics, from boreal and temperate forests to dry scrub forests and swamps, from sea level to at least 3000 meters elevation. Of all bears, the American Black Bear coexists most easily with humans. Although it occurs in just three countries (albeit large ones: Canada, the United States, and Mexico), its total population is greater than that of all other bears combined.

    Asiatic Black Bear: The Asiatic Black Bear has distinctive large "Mickey Mouse" ears. In Asia, Asiatic Black Bears dominate the temperate deciduous forest. In parts of China and the Russian Far East, where Brown Bears and Asiatic Black Bears both occur, the former tend to live in coniferous forests at higher elevations whereas the latter tend to live in broad-leaved forests at lower elevations.

    Both Asiatic Black Bears and Sun Bears are found in the tropical forests of Southeast Asia, where they co-occur in lowland semi-evergreen, mixed deciduous, and dry dipterocarp forests. Asiatic Black Bears are far more common than Sun Bears in montane evergreen forests above 1200 meters, perhaps due to the scarcity of termites, an important food for Sun Bears when fruit is scarce. Sun Bears range as far west as the tropical wet evergreen forests of eastern India, where they coexist with both Asiatic Black Bears and Sloth Bears, although it is not clear whether the three ever occur ogether in a single patch of forest. The tropical evergreen forests of lower Peninsular Malaysia, Borneo, and Sumatra are occupied only by Sun Bears.

    Sloth Bear: The tropical and mainly dry forests, scrub, and thorn woodlands of peninsular India and Sri Lanka are occupied only by Sloth Bears. In some areas, forest cover has been so decimated that Sloth Bears may seek shelter in boulder fields, emerging only at night to forage, often in agricultural fields. They also live in alluvial grasslands on the Indian subcontinent, where termites (a preferred prey) are abundant. At higher elevations, in the Himalayas of northern India, Nepal, Pakistan, and Afghanistan, Sloth Bears are replaced by Asiatic Black Bears in the foothills and by Brown Bears higher up (Asiatic Black Bears are replaced near the treeline by Brown Bears, which extend well into the alpine tundra; Brown Bears also occur throughout the mostly treeless Tibetan Plateau). Sloth Bears (which were mistakenly classified as sloths two centuries ago) have a shaggy coat, small molars, and a gap in their teeth through which they suck termites (they lack the inner upper incisors). They dig for termites and ants with their long, straight claws and also eat fruit, collected mainly from the ground.

    Brown Bear: Brown Bears are so large they face little danger from predators other than other Brown Bears. Despite their imposing bulk, however, they subsist mainly on plant matter, although larger individuals may be more reliant on meat. Bear species often exhibit variation in coat patterns (for example, Black Bears can be black, brown, or even white), but this phenomenon is especially striking in Brown Bears—so much so that early naturalists thought there were some 80 species in North America alone (the "Grizzly Bear" among them). The Brown Bear occurs in North America, Europe, and Asia (and formerly in North Africa). It has the largest range (in terms of latitude, longitude, and elevation), and occupies the greatest diversity of habitats, of any bear species. All other bear species occupy a single continent (or, in the case of the Polar Bear, a single geographic region).

    Polar Bear: Polar Bears have a thick layer of fat and dense fur that insulates them in the icy waters of the Arctic. They are very capable swimmers and are often considered marine mammals (although they can stay underwater for just two minutes). Some individuals stay near shore whereas others are more pelagic, but all depend on ice as a platform for hunting seals. Under its thick fur, a Polar Bear's skin is black; the "white" fur is actually translucent. Polar Bears and Brown Bears are closely related and occasionally hybridize. Although some individual Brown Bears may be larger than any Polar Bear, Polar Bears are generally larger than Brown Bears, making the Polar Bear the largest bear. They are almost entirely carnivorous. Polar Bears can have enormous home ranges. One female was tracked traveling from Alaska to Greenland (males are difficult to track since their heads are smaller than their necks, making it difficult to secure a radio collar).

    Conservation Status

    The conservation status of bears varies greatly among species. Populations of the American Black Bear have actually increased in recent decades.  Brown Bears in North America and parts of Europe are also doing well. In stark contrast, most bear populations in southern Asia (especially Southeast Asia) and probably South America are declining due to habitat loss and poaching. Six of the eight bears (all but American Black Bear and Brown Bear) have been listed as globally threatened on the IUCN Red List (the Giant Panda as Endangered and the others as Vulnerable)—all due to human impacts.

    (Garshelis 2009 and references therein)http://www.biomedcentral.com/1741-7007/10/12

Distribution

    Distribution
    provided by Animal Diversity Web

    Bears are found on all continents except Antarctica and Australia, but are primarily found throughout the northern hemisphere, historically occurring as far south as the Atlas Mountains of northwestern Africa, the Andes of South America, and the Sunda shelf region. This range has been reduced in historical times as a result of human persecution and habitat destruction. For example, brown bear (Ursus arctos) populations in the Atlas Mountains are thought to be extinct and their range has been significantly altered in North America and Europe.

    Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); neotropical (Native )

Morphology

    Morphology
    provided by Animal Diversity Web

    Bears are large, robustly built animals. The smallest species, Helarctos malayanus ranges in size from 25 to 65 kg, the largest individuals can weigh up to 800 kg (Ursus maritimus). Males are larger than females, sometimes more than twice their size. Bears have small, rounded ears, small eyes, and very short tails. Most species have long, rough fur, and the hairs that make it up are generally unicolored (rather than being agouti, the common pattern among mammals). Sun bears have a smooth coat. Most bears are brown, black, or white; some have striking white marks on the chest or face. Giant pandas are well-known for their distinctive bands of black and white fur. Bear skulls are massive, with unspecialized incisors, elongate canines, reduced premolars, and bunodont cheek teeth. All bear species possess robust, recurved, non-retractile claws that they use for digging and ripping. The feet of bears are plantigrade, and most have hairy soles, although tree climbing bears, such as Helarctos, have naked soles. There are five digits on each foot. Giant pandas (Ailuropoda melanoleuca) have an additional, opposable feature of the forepaws, sometimes called a panda's "thumb". It is not a true digit but a pad-covered enlargement of the radial sesamoid bone. Pandas use this opposable structure to manipulate bamboo.

    The skulls of bears are elongated. They have an alisphenoid canal, and the paroccipital processes are large and not fused to the bullae, which are not enlarged. Curiously, the lacrimal bone of bears is vestigial. Their cheekteeth are bunodont, and the carnassials are flattened and specialized for crushing, not secodont. The incisors are unspecialized; the canines are long and slightly hooked; and the first three premolars are small and weakly developed if present at all. The dental formula is 3/3, 1/1, 3-4/4, 2/3 = 40-42.

    Technical characters

    Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

    Sexual Dimorphism: male larger

Habitat

    Habitat
    provided by Animal Diversity Web

    Bears occur in nearly all terrestrial habitats throughout their range, from Arctic tundra and polar ice floes to tropical and temperate forests, mountains, grasslands, and deserts. Although some bear species occur in arid areas, proximity to water is important. Bears are most abundant and diverse in temperate and boreal regions. Most species are habitat generalists, changing preferred foods, activity patterns, and denning quarters with local conditions. Ailuropoda melanoleuca, however, is found primarily in the montane bamboo forests of southern China.

    Habitat Regions: temperate ; tropical ; polar ; terrestrial

    Terrestrial Biomes: tundra ; taiga ; desert or dune ; savanna or grassland ; chaparral ; forest ; rainforest ; scrub forest ; mountains

Trophic Strategy

    Trophic Strategy
    provided by Animal Diversity Web

    Bears are omnivorous and opportunistic. Specific food types may vary by habitat or season. For example, North American brown bears (Ursus arctos) may rely extensively on fruits and insect larvae throughout the year, or may prey extensively on calves during ungulate breeding seasons and on migrating fish. Most species eat primarily fruits and insect larvae but will include vertebrates when they can, carrion, honey, forbs and grasses, seeds, nuts, tubers, fish, and eggs. Bears use their formidable strength, massive forelimbs, and robust claws to tear apart logs and capture prey. Giant pandas (Ailuropoda melanoleuca) are dietary specialists, eating primarily bamboo stems and shoots, but will also include small vertebrates, insects, and carrion in their diet. Polar bears (Ursus maritimus) are the most carnivorous species, preying mainly on seal species, but including fish, small mammals, birds and their eggs, and will scavenge carcasses of whales, walruses, and seals.

    Primary Diet: carnivore (Eats terrestrial vertebrates); herbivore (Folivore ); omnivore

Associations

    Associations
    provided by Animal Diversity Web

    All bear species, because of their omnivorous diet and large size, impact the populations of prey animals and plant communities in the ecosystems in which they live. Polar bear populations and brown bear populations that rely on large prey, exert significant pressure on prey populations, including breeding seals and elk. Bear species may help to disperse seeds from the fruits they eat. Arctic foxes (Vulpes lagopus) rely heavily on scavenging polar bear kills.

    Bears are infected by a wide variety of endo and ectoparasites, including: protozoans (Eimeria and Toxoplasma), trematodes (Nannophyetus salminicola, Neoricketsia helminthoeca), cestodes (Anacanthotaenia olseni, Mesocestoides krulli, Multiceps serialis, Taenia species, and Diphyllobothrium species), nematodes (Baylisascaris transfuga, B. multipapillata, Uncinaria yukonensis, U. rauschi, Crenosoma, Thelazia californiensis, Dirofilaria ursi, Trichinella spiralis, and Gongylonema pulchrum), lice (Trichodectes pinguis), fleas (Chaetopsylla setosa, C. tuberculaticeps, Pulex irritans, and Arctopsylla species), and ticks (Dermacentor and Ixodes species). Infection by Trichinella spiralis is especially common, affecting up to 60% of Ursus maritimus and U. arctos.

    Ecosystem Impact: disperses seeds

    Mutualist Species:

    • Vulpes lagopus

    Commensal/Parasitic Species:

    • Trichinella spiralis
    • Eimeria
    • Toxoplasma
    • Nannophyetus salminicola
    • Neoricketsia helminthoeca
    • Anacanthotaenia olseni
    • Mesocestoides krulli
    • Multiceps serialis
    • Taenia
    • Diphyllobothrium
    • Baylisascaris transfuga
    • B. multipapillata
    • Uncinaria yukonensis
    • U. rauschi
    • Crenosoma
    • Thelazia californiensis
    • Dirofilaria ursi
    • Gongylonema pulchrum
    • Trichodectes pinguis
    • Chaetopsylla setosa
    • C. tuberculaticeps
    • Pulex irritans
    • Arctopsylla
    • Dermacentor
    • Ixodes
    Associations
    provided by Animal Diversity Web

    Once bears reach their adult size it is unlikely that they will be subject to predation. Cubs are at risk of predation from conspecific bears, sympatric bear species, and other large predators, such as large cats and canids. Female bears are aggressive in defense of their young.

    Known Predators:

    • conspecific and sympatric bears
    • large cats (Felidae)
    • social canids (Canidae), such as wolves (Canis lupus)

Behavior

    Behavior
    provided by Animal Diversity Web

    Vision and hearing in bears is not well-developed, but they have a keen sense of smell and use their sensitive lips to locate and maneuver food. Ursus americanus has color vision and has been demonstrated using vision to distinguish food items at close range. Little is known about communication in bears, but grunts, moans, and roars are known from most species. Cubs may be especially vocal, uttering "woofs" and shrill howls when distressed. "Chuffing" is used as a greeting in Ursus arctos. Chemical cues may be used by males in locating receptive females. Home range boundaries, individual identity, and sexual condition may be advertised, both visually and chemically, by tree-scratching and by urinating and defecating on boundary trails.

    Communication Channels: acoustic ; chemical

    Perception Channels: visual ; tactile ; acoustic ; chemical

Life Expectancy

    Life Expectancy
    provided by Animal Diversity Web

    Bears are long-lived if they survive their first few years of life. Most mortality occurs in young cubs or dispersing juveniles as a result of food stress. Pre-weaning cub mortality was estimated at 10-30% in polar bears and sub-adult mortality at between 3 and 16%. In American black bears in Alaska, sub-adult mortality was estimated at 52 to 86%. Estimates of longevity in the wild are as high as 25 years. Captive animals have been known to live to 50 years or more (Ursus arctos).

Reproduction

    Reproduction
    provided by Animal Diversity Web

    Male and female bears generally associate only briefly for mating. Males monitor the estrus condition of females in their home range and will remain close for a few days when females are receptive. Multiple mating is practiced by both sexes.

    Mating System: polygynandrous (promiscuous)

    Bears give birth to 1 to 4 young, usually 2, at intervals of 1 to 4 years. There is evidence of delayed implantation in all species. Gestation lengths ranging from 95 to 266 days, with implantation being delayed from 45 to 120 days. Actual gestation lengths may be closer to 60 to 70 days. Births in temperate species occur during the winter when the female is dormant. The cubs nurse during the dormant period and the entire metabolic demands of the female must be met by her fat reserves. Births in Helarctos malayanus may occur at any time of the year. Sexual maturity occurs at from to 3 to 6.5 years old, usually occurring later in males. Growth continues after sexual maturity. Males may not reach their adult size until 10-11 years old. Females reach adult sizes usually around 5 years old.

    Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous ; delayed implantation

    Females give birth to their young in protected areas, often a den of some kind, until they are capable of getting around well, at several months of age. Bears are very small when born, from 90 (Ailuropoda melanoleuca) to 680 (Ursus arctos) grams at birth. They are born with their eyes and ears closed and are either naked or with only a fine layer of fur. Cubs grow rapidly, polar bears go from 600 grams at birth to 10 to 15 kg within 4 months. Weaning occurs from 3.5 (Ursus thibetanus) to 9 (Ailuropoda melanoleuca) months. Young stay with their mother for up to 3 years, but young of most species disperse after 18 to 24 months. Females are very protective of their young and it is likely that cubs learn about obtaining food and shelter during their extended juvenile time with their mother.

    Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning

Conservation Status

    Conservation Status
    provided by Animal Diversity Web

    Bears have been hunted and persecuted throughout human history. Most bear populations continue to face hunting pressure and have become fragmented as a result of human habitat destruction and hunting.

    The IUCN ranks Malayan sun bears (Helarctos malayanus) as data deficient, polar bears (Ursus maritimus) as lower risk, Asiatic black bears (Ursus thibetanus), sloth bears (Melursus ursinus), and spectacled bears (Tremarctos ornatus) as vulnerable, and giant pandas (Ailuropoda melanoleuca as endangered.

    Several brown bear subspecies are listed as endangered under the United States Endangered Species Act: Mexican grizzly bears, Ursus arctos nelsoni, European brown bears, U. arctos arctos, and Tibetan brown bears or horse bears, U. arctos pruinosus. Baluchistan bears, Ursus thibetanus gedrosianus, are also considered endangered.

    The following species are on Appendix I of CITES: Ailuropoda melanoleuca, Helarctos malayanus, Melursus ursinus, Tremarctos ornatus, Ursus thibetanus, and populations of Ursus arctos in Bhutan, China, Mexico and Mongolia. All other populations of U. arctos are included in Appendix II.

Benefits

    Benefits
    provided by Animal Diversity Web

    Bears are often implicated in predation on livestock, although their impact on livestock populations is most often vastly over-stated. This is particularly true of Tremarctos ornatus, which is persecuted for livestock predation despite its primarily frugivorous lifestyle. Bears regularly attack and kill humans when they feel threatened. Females accompanied by their young may be especially aggresssive and unpredictable. Bear attacks that seem at first to be unprovoked, often prove to be inadvertently provoked when investigated. Bears that live near humans, or have become habituated to humans, cause damage by breaking into homes, food stores, and garbage. Some bear species damage crops, such as manioc and corn.

    Negative Impacts: injures humans (bites or stings); crop pest

    Benefits
    provided by Animal Diversity Web

    Bears are important members of healthy ecosystems and are sometimes used as indicator species of habitat health and wildness. Bears have also been hunted by humans throughout history for their meat, fat, and fur. Other body parts are used in traditional Chinese pharmacopias, although their usefulness in curing ailments has never been demonstrated. Research on the metabolic pathways black bears use during their winter torpor may help in the development of treatments for kidney failure, gallstones, severe burns, and other illnesses.

    Positive Impacts: body parts are source of valuable material; research and education

Other Articles

    Untitled
    provided by Animal Diversity Web

    The fossil record of bears in North America and Eurasia extends to the earlyl Miocene. It is thought that bears reached Africa in the late Miocene and South America in the early Pleistocene.