|
Post by brobear on May 3, 2017 7:02:17 GMT -5
DIET & FEEDING (Craighead 1995) (Hilderbrand et al 1999) (Mattson & Merrill 2002) (Mowat & Heard 2006) (Murie 1985) (Sacco and Van Valkenburgh 2004) (White et al 1998) (Xu et al 2006) (Zager and Beecham 2006) Before radio-collars and satellite telemetry use for tracking by researchers, North American bears viewed as mainly scavengers Brown Bears are omnivores. Recent studies show a more carnivorous diet than more omnivorous American and Asiatic Black Bears, Sun Bears, and Andean Bears. (Sacco and Van Valkenburgh 2004) Prey typically on juvenile ungulates and small, burrowing rodents. Extreme size difference with prey - may be up to 100 times heavier than prey Use brute strength rather than specialized killing techniques to dispatch prey In Mt .McKinley National Park bears ate voles, lemmings, mice, ground squirrel. (Murie 1985) On Tibetan Plateau, eat mainly meat; pika are the prey. (Xu et al 2006) Have the capacity to also take much larger prey such as moose, muskoxen, caribou, elk. pronghorn, deer, bison (Murie 1985) (Craighead 1995) (Mowat & Heard 2006) Calves are preferred but adults sometimes taken (Zager and Beecham 2006) Caribou in Arctic provide significant portion of terrestrial meat (not salmon) in diet Salmon important component of diet in Pacific coast of North America. (Mowat & Heard 2006) (Zager and Beecham 2006) In coastal areas, salmon provide the main source (greater than 50%) of nutrients for Brown Bears. Season in which meat is consumed determines how it is metabolized: (Hilderbrand et al 1999) In spring bears convert meat to lean body mass In fall, bears convert excess protein to fat In addition to carnivorous habits, consume a wide variety of plant and animals, seasonally available (Craighead 1995) (Murie 1985) (White et al 1998) Berries, Whitebark Pine seeds in Yellowstone ecosystem (important for laying on stores of fat for winter) Sedges, grasses, horsetail (Equisetum) Dig and eat underground stores of roots and tubers cached by mice. Army cutworm moths (noctuids) sought on high mountain rocky slopes. Honey In Yellowstone region, Whitebark Pine trees currently severely threatened by disease and a warming climate; major concern for grizzly well-being.(Mattson & Merrill 2002). Search for food with a wide variety of techniques, using "intelligence, curiosity, determination, skills, memory and endurance" (Huber 2010) Turning over rocks Plucking rotten logs and anthills (for ants) Digging for tubers and invertebrates Catching for small mammals Stalking and capturing ungulates After having eaten its fill, bear may cache remaining carcass by covering it with soil, sod, or rocks. Largest bears have priority when a carcass is discovered; subordinate bears wait
|
|
|
Post by brobear on May 3, 2017 7:03:49 GMT -5
REPRODUCTION & DEVELOPMENT (Craighead et al 1995) (Kurt 1990) (Pasitschniak-Arts 1993) (Schoen 1999) (Schwartz et al 2003) Courtship Polygamous Several males may mate with one female. Females may mate with more than one male. Female estrus is about 10-30 days; period is split by a short time of no receptivity. Breeding activity occurs mid-May to July. Reproduction (Craighead et al 1995) Lowest reproductive rate of any land mammal in North America. (Schoen 1999) Females don't breed till 5-6 yrs. Average of 2 cubs/litter 3-4 years between litters In a study of Yellowstone Grizzlys, dominant males did not have sole access to estrus females. Surprisingly, only 27.6 % of all matings observed were between alpha or beta males and females Rest of matings were between lower-status males and females Alpha males usually preoccupied with fighting Alpha males spend more time checking fertility status of females (by sniffing) Perhaps acquire access to females at the best time for fertility Each cub in a litter can have a different father 33% of all litters studied had multiple sires. Females have delayed implantation of embryo after fertilization Allows for timing of birth with favorable environmental conditions. Normally implantation is in November, around 6 weeks before birth. Females and males enter individual dens Females line den floor with mosses and grasses; give birth while hibernating Reproductive biology similar to that of Black Bears. Gestation 6-7 months; occasionally 9 months (Kurt 1990) Life Stages Birth January-March (Schwartz et al 2003) Most litters 2 cubs; up to 4 cubs known. (Craighead et al 1995) Birth weight: 400-500 g (14-18 oz) (Kurt 1990) At birth: closed eyes, little hair, helpless (altricial) Infant (< 1 year old) Remain with mother in den after birth By 3 months weigh 15 kg (33 lb) During 1st summer, young have white chest patch of fur Juvenile Young nurse 1.5 - 2.5 years. Subadult Young may remain with mother up to 3 or 4 years. Adult Sexual maturity: males - 5.5 years; females - 3.5 years Females breed at ages 3 to 8; varies depending on locality and food supply. Longevity About 25 years. (Pasitschniak-Arts 1993) 20 yrs. in wild; 30 in captivity (Kurt 1990) but possibly 50. A European Brown Bear born at the Leipzig Zoo, Germany lived 39 years. (Weigl A Hokkaido Brown Bear died at 39 years at the Odawara Zoo in Japan. A female at Yellowstone National Park gave birth to cubs at age of 22.5 years (Craighead et al 1995) Two years later juveniles were weaned. Average lifespan at Yellowstone National Park is only 6 years. Mortality (Pasitschniak-Arts 1993) Human hunters and human-caused habitat disturbances Severe winters, malnutrition and canabalism cause some deaths Very rarely, tigers in Russia attack bears (and vice versa) Rarely, bears are gored by large ungulates. Infanticide most common cause of natural death in a study of 100 bears in Sweden (Morner et al 2005)
|
|
|
Post by brobear on May 3, 2017 7:04:23 GMT -5
MANAGED CARE (Huber 2010) (Itoh et al 2010) (Law & Reid 2010) Numbers of bears in captivity needs to be managed by two-pronged focus: Restricting captive reproduction to avoid unwanted bears Conservation measures to enhance natural habitats Bears in captivity need to exercise their great capacity for foraging for long periods of time; without this stimulation they are "purposeless and unchallenged." (Law & Reid 2010) Bears in a captive environment need as much physical and mental enrichment as do primates. (Law & Reid 2010) In a new enrichment strategy as of 2010, 2 exhibit spaces conncected for two young Grizzly Bears and an elderly Manchurian Brown Bear at the San Diego Zoo. The bears now take turns using the whole area. This intelligent and highly curious species benefits greatly from varied and new activities and a chance to smell tracks left by other bears. At the Ueno Zoological Gardens in Tokyo, Japan a Japanese Black Bear successfully hibernated during the winters of 2006/2007 and again in 2007/2008. (Itoh et al 2010) Time spent hibernating: 89 days; 68 days - within normal ranges for these bears. Body mass decreased by 20%, a normal loss compared to bears in the wild. This management strategy seen as enriching for the bears and of educational value for the zoo visitors Captive-born bears should not be released into the wild. (Huber 2010) Bears can only learn survival skills from their mother, in their natural habitat. Only exceptions to the above: if orphaned cub had a mother for at least 6 months and the time was early summer; even so, a slim chance of survival as a free-ranging bear. Bears seem to have fewer inherited skills and more learned skills than other carnivores
|
|
|
Post by brobear on May 3, 2017 7:05:42 GMT -5
POPULATION AND CONSERVATION STATUS (Federal Register 1975, 2007, 2010) (McLellan et al 2008) (Proctor et al 2005) (Servheen 1999) Population Status World population estimated: greater than 200,000 individuals (McLellan 2008) Russia - more than 100,000 U.S. - 33,000 Over 500 in and near Yellowstone National Park Canada - 25,000 Europe - 14,000 Several very small isolated populations Japan - possibly up to 2,000 ISIS captive population Conservation (Herrero 1994) (McLellan et al 2008) (Servheen 1999) IUCN Status: Lower Risk/least concern. (1996) CITES Status: CITES I in central Asia (Mongolia, China, Nepal, Bhutan) CITES II rest of world (except Alaska) CITES IIB for Alaskan populations State of Alaska status: classified as 'big game"; may be legally killed by residents, no-residents, and subsistence hunters with licenses U.S. Fish and Wildlife Endangered Species Act (Federal Register 1975) 1975 Threatened in lower 48 states (for discussion see www.fws.gov/mountain-prairie/species/mammals/grizzly/)2007 - Yellowstone population no longer meets USFW definition of threatened. (Federal Register 2007) 2009 - Yellowstone population relisted as threatened. (Federal Register 2010) Survey work to determine numbers and distribution urgently needed in Afghanistan; currently on Afghanistan's Protected Species List. U. S. Fish and Wildlife Service in 2000: (Schwartz et al 2003) Grizzly Bear Recovery Progam aims to restore grizzlys with a cooperative effort to a core widerness area of 14,983 sq km (6785 sq mi) in central Idaho and western Montana. Threats to survival (McLellan et al 2008) (Proctor et al 2005) Hunting by humans for sport, or unsustainable control measures. Poaching for commercial trade in gall bladders and paws, especially in Russian Far East North America may be next source of bear organs for medicinal uses unless belief systems change, or legal penalties provide limits to exploitation. (Servheen 1999) Destruction and fragmentation of habitats leads to vulnerable small populations. Causes of fragmented habitats: Highways Hydroelectric developments Plantation forestry Agriculture Bears' attraction to areas with human foods Factors impacting salmon survival which in turn threatens some grizzly populations: (Mowat & Heard 2006) Global climate change Overfishing Hydroelectric plants Destruction of salmon spawning habitats (Mowat & Heard 2006) Lack of reliable bear population estimates for sound management practices Size of home range may require extensive cooperation between management units and countries (Herrero 1994)
|
|
|
Post by brobear on Jan 10, 2018 16:46:45 GMT -5
library.sandiegozoo.org/factsheets/brown_bear/brown_bear.html TAXONOMY & NOMENCLATURE (Agnarsson et al 2010) (Bonn et al 2008) (ITIS 2010) (Krause et al 2008) (Leonard et al 2000) (Lindqvist et al 2010) (Yu et al 2007) (Pasitschniak-Arts 1993) Describer (Date): Linnaeus 1758 Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Suborder: Caniforma (Dog-like carnivores) Family: Ursidae (Bears) Genus: Ailuropoda (Giant Panda) Genus: Helarctos (Sun Bear) Genus: Melursus (Sloth Bear) Genus: Tremarctos (Spectacled Bear) Genus: Ursus(Bears) Species: Ursus maritimus (Polar Bear) Species: Ursus americanus (American Black Bear) Species: Ursus thibetanus (Asian Black Bear) Species: Ursus arctos (Brown Bear, Grizzly Bear)
|
|
|
Post by brobear on Jan 10, 2018 16:47:45 GMT -5
Taxonomic History and Nomenclature Common Name: Brown Bear, Grizzly Bear, Kodiak Bear Scientific Name: Ursus is Latin for "bear"; arctos comes from Greek arktos, meaning bear. Eight species of bears generally recognized. (Yu et al 2007) Above taxonomy according to Integrated Taxonomic Information System (ITIS); downloaded April 2010. 16 subspecies listed for Brown Bears (Ursus arctos) Other taxonomists say populations in Eastern Europe, Siberia, Alaska, Canada, and the U.S. are probably not genetically distinct enough to merit separate taxonomic designation. (Leonard et al 2000) Sun and Sloth Bears usually classified in their own separate genera Mitochondrial DNA evidence, however, says they belong in Ursus along with the 4 other bear species. (Krause et al 2008, Yu et al 2007, Agnarsson et al 2010) Brown Bears have traditionally been referred to as Grizzly Bears in the non-coastal western U.S. Phylogeny (Krause 2008)(Yu et al 2007) Origins of the Ursidae family: 15-20 million years ago (mid-Miocene). Brown Bears (includes Grizzly Bears) and Polar Bears diverged from the Black and Sun Bears in the last 6.1 million years ago (Pliocene). An ancestor of Brown and Polar Bears diverged from the European Cave Bears (U. spelaeus) around 1.6 million years ago. (Bon et al 2008). Cave Bears are sister to a clade of Brown and Polar Bears. (Agnarsson et al 2010) Estimates vary widely for timing of Brown Bear and Polar Bears divergence. (Lindqvist et al 2010) 1,320,000 to 200,000 years ago. First Brown Bears lived in China, about 500,000 years ago. (Pasitschniak-Arts 1993) Brown Bears and Cave Bears lived at the same time in Europe beginning about 250,000 years ago.(Pasitschniak-Arts 1993) Brown Bears replaced Cave Bears in Great Britain about 10,000 years ago. Brown Bears first appeared 50-70,000 years ago in eastern Beringia (land bridge between Siberia and Alaska during Pleistocene Ice Ages) (Leonard et al 2000) By about 36,000 years ago three main clades of brown bears in Beringia. From Beringia, Brown Bears spread into Canada, Alaska, and the lower U.S. Appeared in lower U.S. 13,000 years ago, at end of last Ice Age when ice-free corridor available. Polar Bears are closest relatives of Brown Bears. Polar-Bear/ Grizzly hybrids are fertile (Davis 1950)
|
|
|
Post by brobear on Jan 10, 2018 16:48:47 GMT -5
Distribution (McLellan et al 2008) Most widespread bear in the world. Europe Middle East Asia Western Canada and western U.S. Formerly, distribution much wider. In lower 48 U.S., original range reduced by 98% less than 100 years after arrival of Europeans. (Garshelis 2009) Local and regional extinctions (extirpations) occurred: Northern Mexico (in 1960's) and much of southwestern U.S California (last one shot 1922); still on flag as official state mammal North Africa (in 1500s in Sinai Peninsula of Egypt; survived untill 1800s in Algeria & Morocco) Extinct more than 500 years ago (Belgium, Denmark, Ireland, Jordan, Luxembourg, Monaco, Netherlands, Tunisia, United Kingdom) Extinct during last 500 years (Algeria, Egypt, Germany, Hungary, Israel, Lebanon, Liechtenstein, Mexico, Moldova, Morocco, Palestinian Territory Occupied, Portugal, San Marino, Switzerland) May be extinct in Syria & Bhutan. Very small populations remain in Nepal & Iraq, French and Andorran Pyrenees Mountains. Ranges of Polar and Grizzly Bears overlap in N. Canada, N. Alaska, and Chukotka, Russia:
|
|
|
Post by brobear on Jan 10, 2018 16:49:50 GMT -5
Habitat: Occupy a wide variety of habitats, more than any other bear species. (McLellan 2008) Dry asian steppes Arctic shrublands Temperate rain forests Sea level to 5,000 m (16,404 ft) Habitat use by females with young differs from that of males. (Rode et al 2006) Females with young avoid areas where male bears hunt or fish; Females may frequent areas visited by humans rather than encounter male bears; Infanticide by males is the danger they try to avoid Habitat use varies seasonally. Migrate to higher elevations as plant foods become available Shift to coastal areas and streams, when accessible, for salmon and other fish Move to lower elevations for early berry crops, when present; then move higher to follow ripening fruits
|
|
|
Post by brobear on Jan 10, 2018 16:50:26 GMT -5
PHYSICAL CHARACTERISTICS (Craighead 1979) (Garshelis 2009) (Kurt 1990) (Pasitschniak-Arts 1993) (Sacco and Van Valkenburgh 2004) (Schwartz et al 2003)
Body Weight: Male 130-550 kg (287-1213 lb); Female 80-250 kg (176-551 lb) Head/Body Length: 1-2.8 m (3.3-9.2 ft) Shoulder Height: Up to 1.5 m (5 ft) Tail Length: 60-200 mm (2-8 in)
General A massive bear with small, round eyes and ears, a dished-in snout, distinct shoulder hump, powerful body; only Polar Bears are heavier. Diet largely determines size (Schwartz et al 2003) Largest brown bears have access to meat, Bears with vegetable diet are smaller. Pelage Color varies from pale tan, blond, gold, many shades of brown to near black, and gray or silver. (Pasitschniak-Arts 1993) Black and partial black fur phases in eastern and central Asia. (Garshelis 2009) Grizzly's guard hairs often pale at tips Underfur grown in fall and molted in spring Sexual Dimorphism Males 1.2-2.2 times larger than females - extreme dimorphism. Most likely due to competition between males during breeding season. Other Physical Characteristics Largest Brown Bears - Western Alaska and British Columbia; Kodiak and Admiralty Islands. Teeth and skulls not as specialized for biting and shearing as those of many meat-eating dogs and cats. (Sacco and Van Valkenburgh 2004) No shearing molars (carnassials) Canine teeth long First three premolars small or not present Molars broad, flat Teeth suited for wide variety of food items from insects to large ungulates Most reliable way to distinguish a Black Bear skeleton from that of a Grizzly Bear: (Gordon 1977) Grizzly's 1st molar in lower jaw is longer than 20.4 mm (.8 in) and wider than 10.5 mm (.4 in)
|
|
|
Post by brobear on Jan 10, 2018 16:51:19 GMT -5
Other good ways to distinguish Black and Brown Bears: Grizzly has shoulder hump; Black Bear doesn't Grizzly has "dished' (concave) snout that is shorter than a Black Bear's Grizzly's ears are short and rounded; Black Bears' are larger and more pointed Grizzly's claws are much longer. Eyesight not keen but used for finding berries and nuts Hearing and sense of smell acute. Feet plantigrade (walk "flat-footed"); soles hairy Five digits on each limb Very long slightly curved claws 5-10 cm (2-4 in) Claws used for digging; not well adapted for climbing trees Female has 6 teats Digestive tract similar to other carnivores except for its length (more surface for absorbing plant nutrients) No fat deposits on artery walls (no arteriosclerosis); can gain significant weight in autumn (and lose in spring) with no ill effects. (Craighead 1979) Recent studies suggest bears finely regulate calcium levels in blood and prevent its deposition in artery walls, which in turn prevents plaque build-up. (Gamble 2006) Physiology differs from other carnivores - have a period of winter dormancy (hibernation) with profound changes in body chemistry, metabolism, breathing rate, and moderate changes in body temperature (Schwartz et al 2003) Females with young may loose up to 43% of body mass during denning. (Garshelis 2009) Polar-Bear/ Grizzly hybrids are fertile (Davis 1950)
|
|
|
Post by brobear on Jan 10, 2018 16:52:40 GMT -5
BEHAVIOR & ECOLOGY (Craighead 1979) (Craighead et al 1995) (Garshelis 2009) (Huber & Roth 1997) (Kurt 1990) (McLellan & Hovey 2001) (McLoughlin 2002) (Murie 1985) (Pasitschniak-Arts 1993) (Servheen 1993) (Schwartz 2003) (Weber 1986) (Wilson & Mittermeir 2009)
Activity Cycle (Pasitschniak-Arts 1993) (Garshelis 2009) (Schwartz 2003) North American Brown Bears mostly diurnal (but active in day and night when food is scarce) Less active in day in areas with high human population In Europe, mostly nocturnal due to human presence; young bears more active in day (before having negative experiences with humans) Active at night in summer Active season is compressed into a 5-7 month period
Often build day beds for resting in hidden places with good visibility near feeding locations (Pasitschniak-Arts 1993) Have a yearly cycle of four main behavioral and biochemical changes Hibernate in winter; period varies according local climate Farthest north habitats: up to 7 months On Kodiak Island (mild winters) males may not even den If resources are poor before hibernation time, bears may not have enough body fat to den After denning, for 10-14 days in "walking hibernation" Normal activity May - September Fat accumulation in fall season; food intake and weight increases significantly Territory Size (McLellan & Hovey 2001) (Pasitschniak-Arts 1993) Home range size varies mainly with food resources. (Garshelis 2009) Smallest - 200 sq km (77 sq mi) for males, 100 sq km (37 sq mi) for females in coastal area with abundant food Largest - 8,000 sq km ( 3089 sq mi) for males in Arctic tundra Female home range is smaller than male Other determinants of territory size Age, sex, social status, health Foraging habits Amount of cover, landscape topography, location of sleeping day beds and dens sites Nearness of possible mates Brown Bears defend no territory. Males and females occupy overlapping home ranges. Young female disperse to home ranges 9.8 km (6.1 mi) from mother's home range Males disperse up to 30 km (18.7 mi).
|
|
|
Post by brobear on Jan 10, 2018 16:53:32 GMT -5
Social Groups
General Females with young only lasting social bonds. On occasion two females with young may associate and share care and nursing of young. (Murie 1985)(Craighead et al 1995) Orphaned cubs not adopted by another female do not survive in wild Need to have at least had a mother for 6 months Hierarchy Alpha males dominate. Highest ranking males have best feeding sites and feeding times Females with cubs are willing to challenge even an alpha male. Territorial Behavior No territory defense, but "personal space" vigorously defended by prompt attack Offending bear uses conciliatory posture, vocalizations to indicate no harm intended Mother bears with young extremely defensive; will even attack and kill a male who comes too close. (Craighead 1979). Seasonal movements to areas with abundant food and den sites (Garshelis 2009) May resemble a migration as bears travel along established routes May travel 20 km (12 mi) in 12 hours. Aggression (Craighead et al 1995) (Pasitschniak-Arts 1993) In a study of Grizzly Bears at Yellowstone National Park Females display 7 times more aggressive attacks and threat behaviors towards males than towards females Both male and female bears react aggressively to intrusion into their "personal space" No obvious (to humans) aggression by another bear triggers this response. Male infanticide exists, but is not a significant cause of cub mortality. When fighting, opponents struck in chest and shoulder with paws; bites directed towards head and neck Play (Herrero 1985) Bears of all ages play Chase birds Adults and young deliberately slide and roll down snowy slopes Manipulate objects Young bears wrestle, jump and tumble together
|
|
|
Post by brobear on Jan 10, 2018 16:54:12 GMT -5
Communication
Displays/Visual Signs Raise to full height when threatened Dominance indicated by a full-fronted approach Neck outstretched, ears laid back, canines displayed Subordinance indicated by sideways orientation Head low or turned away or may sit or lie down, or back away Vocalization (Pasitschniak-Arts 1993) With an attack (Kurt 1990) A "high-pitched snorting with open lips" A hoarse barking uttered in short bursts Jaw-beating where teeth of upper and lower jaws are forcefully snapped together With a threat Growl and roar When wounded or in pain or when hungry, lost, cold Distress calls When contented or friendly, as a greeting, as appeasement, during courtship, between female and young. Chuffing - "popping" noise made with lips and cheeks while exhaling Both sexes and all ages use Olfaction/Scent Marking Relies mainly on a sense of smell for information about the environment. (Pasitschniak-Arts 1993) Many researchers think bears do not mark a territory with scats as do many other carnivores. (Weber 1989, Craighead 1979)
|
|
|
Post by brobear on Jan 10, 2018 16:54:54 GMT -5
Hibernation and denning Dens are excavated by males and females as early as September or immediately before use in November. Dens in dug earth have a tunnel about 4 feet long leading to a chamber 5 feet in diameter (Murie 1981) Some dens have no entrance tunnel. (Garshelis 2009) Onset of hibernation spurred by length of day and often by a snow storm. (Servheen 1993) Rocky Mountains den sites: Have deep snow that doesn't melt in temporary winter thaws Are on steep or moderately steep slopes Females and cubs may be vulnerable to snowmobile disturbance during denning and immediately after denning. (Podruzny et al 2002) In Croatia, Dens built in rock cavities, under tree roots, in hollow trees, on the ground under conifers. (Huber & Roth 1997) In barren-ground habitats of Arctic regions: (McLoughlin 2002) Grizzlys dug dens under tall shrubs, using the roots as the den roof Bears carried nesting materials to den Females entered dens earlier than males Both sexes are denning by October Males emerge before females in late April, early May. During denning About 1/3 of females give birth Another 1/3 of denning females are still nursing yearlings (Craighead et al 1995) Adult females remain in a den for at least half the year. (Atkinson & Ramsay 1995) (Folk et al 1976) Locomotion (Craighead et al 1995) (Weber 1986) Favored gait is a slow shuffle. Undisturbed bear walks 5.5-6.0 km/hr (3.4-3.7 mi/hr) Adult bear can gallop at over 56 km/hr (35 m/hr) for 3 km (2 mi). Can trot with average speed of 10-12 km/hr (6.2-7.5 mi/hr) Tree-climbing: (Wilson & Mittermeir 2009) All juvenile Brown Bears can climb trees Adults in North America rarely climb trees (Black Bears do climb trees) Adult Brown Bears in Europe and Asia climb trees Often stand while stopped Use trails that are shortest distance between feeding and resting areas May hesitate 20 minutes while assessing an exposed area before entering open space.
|
|
|
Post by brobear on Jan 10, 2018 16:55:40 GMT -5
Interspecies Interaction (Murie 1985) (Podruzny et al 1999) (Mowat & Heard 2006) Grizzly bears and Brown Bears naturally adapted to exploiting temporary but abundant food items (Craighead et al 1995) Feasting on whale carcasses or salmon runs are examples Visiting human garbage dumps only an extenstion of this behavior Range overlaps that of American and Asiatic Black Bears (U. americanus, U. thibetanus) May compete with other carnivores for food (Pasitschniak-Arts 1993) Mountain lions Bobcats Lynx Wolves Wolverines Foxes Eagles and ravens attempt to scavenge bears' kills Also may make kills because of bears' attempts to catch small rodents Population densities of Brown Bears in Arctic are greater when they have access to abundant caribou. Observations by Murie (1985) at McKinley National Park: Caribou populations are culled by grizzlys - calves, old, diseased, and remains of wolf-killed carcasses all enrich Grizzly's diets. Moose calves preyed upon by grizzlys; a female moose attacks bears to protect calf Grizzlys rarely have an opportunity to kill Dall Sheep; carcasses of these sheep occasionally add to the grizzly diet Ground squirrels often caught above ground and below, in burrows Considerable effort sometimes required, lasting up to 40 minutes in one observation Whitebark Pine habitat vital to grizzly survival in Yellowstone National Park (Podruzny et al 1999) Habitat serves as refuge. Red Squirrel caches of Whitebark Pine seeds an important grizzly food resource A fungus, the White Pine blister rust, is decimating Whitebark Pine populations in North America.
|
|
|
Post by brobear on Jan 10, 2018 16:56:34 GMT -5
DIET & FEEDING (Craighead 1995) (Hilderbrand et al 1999) (Mattson & Merrill 2002) (Mowat & Heard 2006) (Murie 1985) (Sacco and Van Valkenburgh 2004) (White et al 1998) (Xu et al 2006) (Zager and Beecham 2006) Before radio-collars and satellite telemetry use for tracking by researchers, North American bears viewed as mainly scavengers Brown Bears are omnivores. Recent studies show a more carnivorous diet than more omnivorous American and Asiatic Black Bears, Sun Bears, and Andean Bears. (Sacco and Van Valkenburgh 2004) Prey typically on juvenile ungulates and small, burrowing rodents. Extreme size difference with prey - may be up to 100 times heavier than prey Use brute strength rather than specialized killing techniques to dispatch prey In Mt .McKinley National Park bears ate voles, lemmings, mice, ground squirrel. (Murie 1985) On Tibetan Plateau, eat mainly meat; pika are the prey. (Xu et al 2006) Have the capacity to also take much larger prey such as moose, muskoxen, caribou, elk. pronghorn, deer, bison (Murie 1985) (Craighead 1995) (Mowat & Heard 2006) Calves are preferred but adults sometimes taken (Zager and Beecham 2006) Caribou in Arctic provide significant portion of terrestrial meat (not salmon) in diet Salmon important component of diet in Pacific coast of North America. (Mowat & Heard 2006) (Zager and Beecham 2006) In coastal areas, salmon provide the main source (greater than 50%) of nutrients for Brown Bears. Season in which meat is consumed determines how it is metabolized: (Hilderbrand et al 1999) In spring bears convert meat to lean body mass In fall, bears convert excess protein to fat In addition to carnivorous habits, consume a wide variety of plant and animals, seasonally available (Craighead 1995) (Murie 1985) (White et al 1998) Berries, Whitebark Pine seeds in Yellowstone ecosystem (important for laying on stores of fat for winter) Sedges, grasses, horsetail (Equisetum) Dig and eat underground stores of roots and tubers cached by mice. Army cutworm moths (noctuids) sought on high mountain rocky slopes. Honey In Yellowstone region, Whitebark Pine trees currently severely threatened by disease and a warming climate; major concern for grizzly well-being.(Mattson & Merrill 2002). Search for food with a wide variety of techniques, using "intelligence, curiosity, determination, skills, memory and endurance" (Huber 2010) Turning over rocks Plucking rotten logs and anthills (for ants) Digging for tubers and invertebrates Catching for small mammals Stalking and capturing ungulates After having eaten its fill, bear may cache remaining carcass by covering it with soil, sod, or rocks. Largest bears have priority when a carcass is discovered; subordinate bears wait
|
|
|
Post by brobear on Jan 10, 2018 16:57:17 GMT -5
REPRODUCTION & DEVELOPMENT (Craighead et al 1995) (Kurt 1990) (Pasitschniak-Arts 1993) (Schoen 1999) (Schwartz et al 2003)
Courtship Polygamous Several males may mate with one female. Females may mate with more than one male. Female estrus is about 10-30 days; period is split by a short time of no receptivity. Breeding activity occurs mid-May to July.
Reproduction (Craighead et al 1995) Lowest reproductive rate of any land mammal in North America. (Schoen 1999) Females don't breed till 5-6 yrs. Average of 2 cubs/litter 3-4 years between litters In a study of Yellowstone Grizzlys, dominant males did not have sole access to estrus females. Surprisingly, only 27.6 % of all matings observed were between alpha or beta males and females Rest of matings were between lower-status males and females Alpha males usually preoccupied with fighting Alpha males spend more time checking fertility status of females (by sniffing) Perhaps acquire access to females at the best time for fertility Each cub in a litter can have a different father 33% of all litters studied had multiple sires. Females have delayed implantation of embryo after fertilization Allows for timing of birth with favorable environmental conditions. Normally implantation is in November, around 6 weeks before birth. Females and males enter individual dens Females line den floor with mosses and grasses; give birth while hibernating Reproductive biology similar to that of Black Bears. Gestation 6-7 months; occasionally 9 months (Kurt 1990)
|
|
|
Post by brobear on Jan 10, 2018 16:57:57 GMT -5
Life Stages Birth January-March (Schwartz et al 2003) Most litters 2 cubs; up to 4 cubs known. (Craighead et al 1995) Birth weight: 400-500 g (14-18 oz) (Kurt 1990) At birth: closed eyes, little hair, helpless (altricial) Infant (< 1 year old) Remain with mother in den after birth By 3 months weigh 15 kg (33 lb) During 1st summer, young have white chest patch of fur Juvenile Young nurse 1.5 - 2.5 years. Subadult Young may remain with mother up to 3 or 4 years. Adult Sexual maturity: males - 5.5 years; females - 3.5 years Females breed at ages 3 to 8; varies depending on locality and food supply. Longevity About 25 years. (Pasitschniak-Arts 1993) 20 yrs. in wild; 30 in captivity (Kurt 1990) but possibly 50. A European Brown Bear born at the Leipzig Zoo, Germany lived 39 years. (Weigl A Hokkaido Brown Bear died at 39 years at the Odawara Zoo in Japan. A female at Yellowstone National Park gave birth to cubs at age of 22.5 years (Craighead et al 1995) Two years later juveniles were weaned. Average lifespan at Yellowstone National Park is only 6 years. Mortality (Pasitschniak-Arts 1993) Human hunters and human-caused habitat disturbances Severe winters, malnutrition and canabalism cause some deaths Very rarely, tigers in Russia attack bears (and vice versa) Rarely, bears are gored by large ungulates. Infanticide most common cause of natural death in a study of 100 bears in Sweden (Morner et al 2005)
|
|
|
Post by brobear on Jan 10, 2018 16:58:28 GMT -5
MANAGED CARE (Huber 2010) (Itoh et al 2010) (Law & Reid 2010) Numbers of bears in captivity needs to be managed by two-pronged focus: Restricting captive reproduction to avoid unwanted bears Conservation measures to enhance natural habitats Bears in captivity need to exercise their great capacity for foraging for long periods of time; without this stimulation they are "purposeless and unchallenged." (Law & Reid 2010) Bears in a captive environment need as much physical and mental enrichment as do primates. (Law & Reid 2010) In a new enrichment strategy as of 2010, 2 exhibit spaces conncected for two young Grizzly Bears and an elderly Manchurian Brown Bear at the San Diego Zoo. The bears now take turns using the whole area. This intelligent and highly curious species benefits greatly from varied and new activities and a chance to smell tracks left by other bears. At the Ueno Zoological Gardens in Tokyo, Japan a Japanese Black Bear successfully hibernated during the winters of 2006/2007 and again in 2007/2008. (Itoh et al 2010) Time spent hibernating: 89 days; 68 days - within normal ranges for these bears. Body mass decreased by 20%, a normal loss compared to bears in the wild. This management strategy seen as enriching for the bears and of educational value for the zoo visitors Captive-born bears should not be released into the wild. (Huber 2010) Bears can only learn survival skills from their mother, in their natural habitat. Only exceptions to the above: if orphaned cub had a mother for at least 6 months and the time was early summer; even so, a slim chance of survival as a free-ranging bear. Bears seem to have fewer inherited skills and more learned skills than other carnivores
|
|
|
Post by brobear on Jan 10, 2018 16:59:04 GMT -5
POPULATION AND CONSERVATION STATUS (Federal Register 1975, 2007, 2010) (McLellan et al 2008) (Proctor et al 2005) (Servheen 1999) Population Status World population estimated: greater than 200,000 individuals (McLellan 2008) Russia - more than 100,000 U.S. - 33,000 Over 500 in and near Yellowstone National Park Canada - 25,000 Europe - 14,000 Several very small isolated populations Japan - possibly up to 2,000 ISIS captive population Conservation (Herrero 1994) (McLellan et al 2008) (Servheen 1999) IUCN Status: Lower Risk/least concern. (1996) CITES Status: CITES I in central Asia (Mongolia, China, Nepal, Bhutan) CITES II rest of world (except Alaska) CITES IIB for Alaskan populations State of Alaska status: classified as 'big game"; may be legally killed by residents, no-residents, and subsistence hunters with licenses U.S. Fish and Wildlife Endangered Species Act (Federal Register 1975) 1975 Threatened in lower 48 states (for discussion see www.fws.gov/mountain-prairie/species/mammals/grizzly/)2007 - Yellowstone population no longer meets USFW definition of threatened. (Federal Register 2007) 2009 - Yellowstone population relisted as threatened. (Federal Register 2010) Survey work to determine numbers and distribution urgently needed in Afghanistan; currently on Afghanistan's Protected Species List. U. S. Fish and Wildlife Service in 2000: (Schwartz et al 2003) Grizzly Bear Recovery Progam aims to restore grizzlys with a cooperative effort to a core widerness area of 14,983 sq km (6785 sq mi) in central Idaho and western Montana.
|
|