TAXONOMY & NOMENCLATURE
(Agnarsson et al 2010) (Ingolfsson & Wiig 2008) (Krause et al 2008) (Yu et al 2007) (Lindquist et al 2010) (O'Brien 2003) (Schliebe et al 2006) (Wozencraft 2005) (Yu et al 2004) (Yu et al 2007) (ITIS 2010)
Describer (Date): Phipps (1774:p.185) A Voyage Towards North Pole,
London: J. Nourse for Ursus maritimus
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order:
Carnivora (15 families) 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 arctos - Brown Bear, Grizzly Bear Species: Ursus thibetanus - Asian Black Bear
Above taxonomy according to ITIS (The Integrated taxonomic Information System uploaded Feb. 2010)
Several recent molecular DNA studies suggest Sun Bears and Sloth Bears belong in the genus Ursus. (Agnarsson et al 2010) (Krause et al 2010)
Polar Bear - Ursus
maritimus from the Latin for "bear of the sea" (maritime bear)
Ah tik tok - Alaskan Eskimo name meaning "those that go down
to the sea"
Many common names throughout Arctic: nanook, ice bear, sea bear.
Phylogeny (Yu et al 2007) (Yu et al 2004)
(Schliebe et al 2006)
Molecular data indicate that the procyonid (raccoons, koatis, ringtails, kinkajous and others) and bear families diverged
from each other about 30 million years ago (Oligocene).
Giant Pandas separated from other bears around 12 million years ago (Miocene).
Around 11 million years ago the spectacled bears split from the
other bears (Miocene).
Lineages leading to the 6 distinct living bear species in Ursus radiated from a common ancestor 6.3 million years ago (Pliocene).
Brown Bears (includes Grizzly Bears) and Polar Bears diverged from the Black and Sun Bears in the last 6.1 million years ago (Pliocene).
Range overlap of Polar and Grizzly Bears only in N. Canada, Chukotka, Russia and N. Alaska.
A few Polar-Bear, Grizzly hybrids have been seen in western Canadian Arctic; a second generation hybrid whose mother was already a polar-grizzly hybrid confirmed in 2010
Polar Bears diverged from one group of brown bears about 150,000 years ago according to molecular evidence (Lindquist et al 2010)
1.32 million years ago (Pleistocene)
according to complete mitochonrial DNA evidence (Yu et al 2007)
Few Polar Bear fossils have been found, because they live on the ice and their remains fall to the bottom of the ocean or are scavenged.
In 2004 a well-preserved 110,00-130,000-year-old jawbone and canine tooth were discovered in the Svalbard archipelago of Norway providing DNA (Lindqvist et al 2010)
Early Polar Bear fossils known from
100,000 year-old Pleistocene sediments in Kew
Botanical Gardens in London
Polar Bears and Grizzly Bears are the closest relatives (sister clade to) the extinct Cave Bear (U. speleaus). (Agnarsson et al 2010)
DISTRIBUTION & HABITAT
(Amstrup & Gardner 1994) (DeMaster & Stirling 1981) (Derocher et al 2004) (Durner et al 2006) (Stirling 1993) (Travis 1994)
Circumpolar distribution throughout Arctic.
Primary habitat: North Polar Basin, annual sea ice fields attached to shorelines.
Evolutionarily adapted to sea ice; most remain on ice year-round, spending only short periods on land (Only 7% of Polar Bears' time is spent on land, mostly in maternal dens).
A few bears occupy permanent pack ice found in the central Arctic basin.
Not evenly distributed throughout range on sea ice; show preference for certain sea ice characteristics (Stirling 1993) and location (near continental shelf). (Derocher 2004)
Most abundant near shore (in shallow water areas) where currents increase marine productivity and keep the ice cover from becoming too consolidated in winter.
Cracks and holes in ice give polar bears access to seals coming up from water below.
Distribution in most areas varies seasonally with extent of sea ice cover and availability of prey.
Suitable sea ice cover has declined in last decades and the decline is accelerating. Sea ice breakup dates in 2004 were 3 weeks earlier than recorded in 1984. Vulnerable young and old bears are highly stressed under such conditions.
Polar Bear denning sites are critical for the survival of the cubs. Most dens are found near the coastlines, with the exception of the Hudson Bay area where they may den as far as 118 km (73 mi) inland; denning sites may also be located on drifting pack ice in many areas
Countries having Polar Bear populations:
United States (Wrangel Island, western Alaska, northern Alaska)
(Amstrup 2003) (Cushing et al 1988) (DeMaster & Stirling 1981) (Derocher et al 2005) (Kurt 1990)
(Nachtigall et al 2007) (Stirling 1993, 1998)
Body Weight: Males occasionally exceed 800 kg (1,760 lbs); Females 150-250 kg (331-551 lb) Shoulder Height: Up to 1.7 m (5.6 ft); Alaskan brown bear nearly the same size. Body Length: Males 240-260 cm (95 -102 in), females
190-210 cm (75 -85 in) Tail Length: 7-12 cm (about 3-5 in)
Largest living bear species — occasionally exceeds 800 kg (1,760 lbs).
Marked sexual dimorphism:
males 2.1 times mass of females (Among mammals only seals and walruses show more dimorphism). (Derocher et al 2005)
Most mammals with extreme dimorphism have more breeding females than males in a population
Polar Bears have three adult males for each breeding female (strong competition for females)
Males have much longer foreleg guard hairs than females; may be attractive to females (as is the male lion's mane) or may make the males look larger to other males.
Neck is long
and very thick (wider than the head); radio collars slip off males - only used on females.
Head is elongated but smaller than that of other bears.
Dentition reflects a strictly carnivorous diet.
Cheek teeth surface area reduced (few plants to grind).
Slicing teeth (carnassials) are well-developed for meat eating.
conical and slightly hooked for grasping prey; male canines very large.
Ears relatively small.
Sensitive hearing over a wide frequency range; respond to Ringed Seals low-frequency vocalizations.
Lack shoulder hump.
Large paddle-like, wide feet.
5 toes on each foot.
Claws non-retractable and are 5-7 cm long.
of feet have small dermal bumps or papillae which may help
with traction on ice.
Females have four functional mammae (other bears have 6).
Large amounts of sub-cutaneous fat.
Adult thickness 5-10 cm.
blubber and pelt provide insulation
Liver is somewhat toxic to humans due to its high levels of vitamin A. (Amstrup 2003)
Able to avoid bone loss during prolonged, continuous hibernation
A unique physiological adaptation for bone building allows a "protective preparation" for hibernation.
Pelage and Skin
Completely covered with fur except for tip of nose; even foot pads are furred in winter.
Have thick layer of underfur (5 cm long) and tufted intermediate
guard hairs (15 cm long)
Distinctive translucent white hair is unpigmented.
Probably arose from light color
phase brown bears that were living on Asian coast of Arctic Ocean.
Color varies with season. Appear whitest after molt, yellowish in summer
due to oxidation by sun or oils from prey
Hairs do not transmit UV light to the skin in order to capture heat energy from the sun (a 1980's "Arctic legend") (Amstrup 2003)
Algal growth inside the shaft of hollow guard hairs of captive bears in
warm climates causes the pelt to have a green appearance.
Nose, skin, and claws are black
BEHAVIOR & ECOLOGY
(Atkinson & Ramsay 1995) (Cushing et al 1988) (DeMaster & Stirling 1981) (Derocher 2010) (Durner et al. 2011) (Ferguson et al 2000) (Folk et al 1976)
(Folk et al 1980) (Ginsburg 1994) (Gittleman 1989)
(Herrington 1963, 1968) (Jonkel et al 1972) (Kurt 1990)
(McGee-Lawrence et al 2008) (Megan 2009)(Messier et al 1994) (Nowak 1981) (Owen 2009) (Schweinsburg 1979) (Stirling 1993, 1998)
(Van de Velde et al 2003)
(Watts and Hansen 1987) (Welch et al. 2014) (Wemmer 1976)
Most active during first third of the day. Least active in last third.
In summer, grooming/washing occurs after 30 minutes of feeding.
Amount of time spent hunting changes depending on availability of seals.
In general less than 2% of hunting attempts are
An experienced adult catches a seal every 4-5 days.
Late February-April: mother and cubs leave den.
Usually remain at den
site for 7-10 days so that cubs can adjust to cold (den may be 20
degrees warmer) and have a chance to exercise.
March-April: adult males begin search for females.
April-May: ovulation induced in female due to intense 1-2 week mating
April-August: bears most active. Ringed Seals give birth in April.
August-September: bears of both sexes dig sleeping pits and temporary dens and remain somewhat sedentary in Canadian Arctic. (Messier et al 1994)
Late October-early November: denning by females.
Delayed implantation of embryo occurs
November-January: females give birth, nurse young in den.
Solitary except for females with cubs.
learn by following and imitating mother during the 2.5 year period
they are with her.
Sexes come together only briefly for up to two weeks during mating season, March-June (may remain together for up to two weeks).
Several bears may scavenge at the same whale carcass but each animal
Most females reproduce only once every 3 years.
Only a third of the females are available during any breeding
Males compete intensely for breeding
Male bears of all species sometimes kill cubs.
Females will defend cubs by challenging or attacking a male twice her size
A 6 month-old cub can outrun an adult male.
In late fall when male bears fast and wait for ice to
freeze, display little aggression but engage in mock ritualized
A "loose dominance hierarchy" among males is based on size; risk of injury in male/male fights is high. (Derocher et al 2005)
More predatory than other bears (less omnivorous).
Locate birth lairs and breathing holes of Ringed Seals by smell and sound.
Approach slowly to minimize their own sound.
May break into lair
immediately or wait motionless for several hours for seal to return.
Studies on captive polar bear hearing indicate that "auditory cues play an important role" (Cushing et al 1988)
Swim underwater to stalk seals lying at the edge of an ice
Hunting in summer months: 77% still-hunting, 23% stalking.
winter and early spring: almost all hunting is still-hunting (far more
successful than stalking).
Small size of major prey probably eliminates any advantage in group
Large numbers of bears scavenge together at a
whale carcass or human garbage dump.
Consume fat of prey first (to get the most calories quickly).
Considerable competition between Polar Bears for a kill; larger bears will run off smaller bears.
Wash and lick themselves while feeding; spend up to 15 minutes grooming
Large overlapping home ranges.
Faithful to general geographic regions.
Do not defend territories.
Home range in some areas of drifting ice pack varies greatly.
May make extensive northern and southern migrations.
Vocalization (Wemmer et al 1976; Cushing et al 1988)
Bear vocalization (and hearing) not well known.
Knowledge of the bears' hearing range important for establishing effects of noise disturbance on these bears. (Owen 2007)
Females and cubs use chuffing call
with each other.
1-32 low intensity sound pulses
emitted in rapid succession
Most frequent in cub's early months.
Chuffing call infrequent in adults; may signal stress/agitation.
Bears snort /chuff, growl, and chomp teeth when aggressive
Captive Polar Bears "groaned and chuffed" when presented with underwater call of Ringed Seals (their favored prey). (Cushing et al 1988)
Preliminary investigations of acoustic communication in Polar Bears indicate they can produce low frequency sounds. (Owen 2009)
Olfactory and visual signals
Highly developed sense of smell.
Detect breathing holes of Ringed Seal from at least 1 kilometer
Use of scents (pheromones) not documented but probably present when males seek females.
male may walk 10 km in a straight line in search of a breeding
Once track crossed, recognition is instantaneous and he will proceed until he catches up to her.
Limited number of visual facial signals.
Facial muscles poorly developed.
Unlike highly social cats and wolves, solitary lifestyle doesn't require elaborate mechanisms for group coexistence.
Most plantigrade (soles flat to the ground similar to humans) of all the Carnivora.
Dogs and cats are digitigrade (stand on
toes with most of sole elevated).
Digitigrade animals tend to be faster than
plantigrade animals partly because of a longer
Top speed recorded: 11 m/sec (25 mph).
Top speed for digitigrade
lion and wolf: 35-40 mi/hr.
Speed sacrificed in favor of
tremendous strength/mobility of limb movement
Prefer lying down and still-hunting to chasing prey due to energy costs of running.
Move with ease and agility over rough terrain and jumbled ice floes.
Nearly all carnivores are excellent swimmers; Polar Bear has
Forelimbs and large forepaws propel animal forward with a stroke like a crawl.
limbs trail behind serving as a rudder.
Head and shoulders held above
Swimming rate about 6.5 km/hr.
Able to swim up to 15 miles easily.
Adapted for swimming near-shore.
Some reports of longer swims
DeMaster and Stirling (1981) - 40
mile swim across open water.
Longer swims, especially in open seas with waves can be dangerous
As ice packs melt, bears in some areas swim farther across open water
Researchers report a radio-collared female in the Beaufort Sea swam continuously for 687 km (426 miles) over 9 days and then swam and walked an additional 1,800 km (1,118 mi); she lost 22% of her body mass and her yearling cub (Durner et al. 2011)
Reports on the increase of bear drownings.
Hibernation and denning
Adult females remain in a den for at least half the year.
(Atkinson & Ramsay 1995)
(Folk et al 1976)
In these months, do not eat, drink, urinate or defecate.
recycled biochemically (without kidneys) to prevent dehydration.
As much as 30% of body mass lost; 43% of body weight
Massive weight gain protects against extended fasting during pregnancy and denning.
Stored fat broken down to supply 90% of energy requirements.
All Polar Bears use dens.
(Van de Velde et al 2003)
- long term use
(Watts and Hansen 1987)
(Messier et al 1994)
For pregnancy, birth, and first months of cubs' life.
Average use: 6 months
Adult females excavate in snow throughout their ranges.
Shelter-dens - short term use
autumn-spring by males and females
(Jonkel et al 1992)
During times of no Ringed Seals, bad weather (including too hot), too many insects or other bears.
Periods varying from 0.5 - 4 months, according data from Greenland in 1920's -1960's. (Ferguson 2000)
Made of snow or earth or natural shelters like caves or even suitable overhanging blocks of ice.
Use in dark winter not easily observed until advent of satellite telemetry (Ferguson et al 2000
Polar Bears alter their physiology throughout the year. (Nelson et al 1980)
Other bears' physiology more tied to seasons.
Switch between feeding and fasting metabolism at any time of year, depending on food supplies.
(Derocher et al 1990)
(Nelson et al 1984)
Begin fasting within 7-10 days after food is gone.
Avoid significant bone loss during prolonged hibernation.
(Lennox and Goodship 2008) (McGee-Lawrence et al 2008)
Sleeping heart rates during hibernation as low as 8-10 beats/minute.
(Folk et al 1980)
40-50 beats/minute in summer.
Polar Bear body temperature during hibernation only slightly lower than their normal.
(Harrington 1968) (Folk et al 1980)
Hibernating body temperature lower in smaller hibernators.
Body temperature may be fine-tuned on a cellular level by varying levels of nitric oxide (Welch et al. 2014)
Genetic differences between polar and brown bears suggest that polar bears may have increased ability to regulate the production of this molecule which can influence whether energy from food is used to power cellular functions (in the form of ATP) or whether it is used to generate heat (thermogenesis)
In bears, the basal metabolic rate varies with climate and season; Polar Bear has highest BMR.
Overheat easily when running; can't travel any
great distance at speeds more than a walk.
Low surface-area to volume ratio
favors heat retention.
Tendency to overheat
enhanced by layer of fat 11 cm (4.5in) thick.
Young cubs up to 6 months old, with little body fat, are susceptible to cold.
Use more than twice the predicted energy for moving at a given speed, perhaps due to bulky body.
Fat and fur both insulate.
As long as bear isn't exposed to wind, body temperature and metabolic rate remain normal at -37
degrees C (-35 degrees F).
Body temperature drops to 31-35 degrees C (88-95 degrees) when in winter dens; this temperature is only slightly below normal body temperature. (Harrington 1968)
Interspecies Interaction (DeMaster & Stirling 1981) (Regehr et al 2007) (Rosing 2006) (Stirling 1977, 1993) (Amstrup 2003)
Polar Bears are the top predators of the Arctic marine ecosystem.
Each year kill about 44% of new-born Ringed Seal pups
Population size largely determined by numbers and availability of Ringed Seals
Ringed Seals, the Polar Bear's primary prey, have evolved into very cautious, vigilant animals; by contrast
Weddel Seals living without ground predators in the Antarctic are comparatively fearless. (Stirling 1977, Amstrup 2003)
Arctic foxes, ravens, gulls scavenge remains of seals killed by Polar Bears
affect Polar Bears by:
Sport hunting by non-native people which provides income to Inuits.
Hunting by native Inuit in Alaska, Canada and Greenland for hides to sell; some hides made into clothing in Greenland.
After local reports of increased bear sightings, in 2005 harvest quota upped 19%
Scientific studies suggest increased sightings due to to changes in food-seeking behavior from nutritional stress, rather than increased overall numbers of Polar Bears. (Regehr et al 2007)
Development for oil and gas lines in maternal denning areas.
Tourism at Churchill, Manitoba to see the bears "in the wild".
Production of PCB's and other pollutants.
Emitting greenhouse gases which cause rapid climate change and loss of Arctic sea ice.
DIET & FEEDING
(Amstrup 2003) (Demaster & Stirling 1981) (Derocher et al 1993) (Derocher et al 2004) (Stirling 1993)
Most carnivorous of all bears.
Giant Panda almost entirely
Sloth bear largely insectivorous.
mixed feeders (omnivores), eating both plants and animals.
Polar Bears often display stereotypic, repetitive pacing behavior in captivity.
Pacing in captive Polar Bears was so well known to the public that in the Dutch language a verb 'ijsberen' describes activity by pacing, restless people as literally 'to Polar Bear' (Clubb & Vickery 2006)
Diverse management strategies can reduce this behavior but does not eliminate it (Swaisgood and Shepherdson 2006)
POPULATON AND CONSERVATION STATUS
(Aars et al 2006) (Amstrup 2003) (Dowsley 2007) (Molnar et al 2010) (Prestrud & Stirling 1994) (Schliebe et al 2006) (Stirling 1993)
(Stirling and Derocher 2007) (Stirling et al 2008) (Servheen 1989) (IUCN 2009)
Listed on CITES Appendix II
Listed on IUCN Redlist (2006) as: Vulnerable
Serious concern began in 1960s after years of increasing hunting.
1965: First international meeting on conservation of Polar Bears in
Fairbanks Alaska. Polar Bear Specialist Group established by IUCN
1972 killing except for native subsistence prohibited by U.S. Marine
Mammal Protection Act
1973: 5 Polar Bear nations, U.S., Canada, Denmark (for Greenland),
Soviet Union and Norway (for Spitsbergen) draft agreement to restrict
hunting, protect habitat and carry out research on Polar Bears (U.S.
ratified in 1976)
1984: Total population in Alaska estimated at 2,000. Hunted by Inuit
natives along north coast. 15 villages took 344 animals between
1988: Agreement signed by native hunters to jointly manage Polar Bear
harvest in Alaska and Canada.
2005: IUCN listed as Vulnerable (A3c) with Decreasing Populations (based on decline in area of occupancy) Version 2009.1
2006: US Fish and Wildlife calls for ban by Canada, Denmark, Norway, Union of Socialist Republics, and United States of "hunting of female Polar Bears with cubs and their cubs" and "hunting of Polar Bears in denning areas during periods when bears are moving into denning areas or are in dens." (Schliebe et al 2006)
2007: Population estimate worldwide: 22,000 (USGS 2007)
2007: USGS in September predicts 2/3 of the population will disappear by 2050 and that Polar Bears will be restricted to the Arctic archipelago of Canada / northern Greenland coast
2008: Listed with U.S. Endangered Species Act as: Threatened
2009: IUCN Polar Bear Specialist Group documented "unprecedented sea ice retreats in 2007 and 2008"
and confirmed earlier conclusion that unchecked global warming will threaten Polar Bears everywhere.
2009: Population estimates for all 19 Polar Bear populations about 20,000 to 25,000 individuals. (IUCN 2009)
Unlike all other bear species, Polar Bears still occupy most of
their original habitat.
2009: Polar Bear Specialist Group reveals that eight Polar Bear population groups are now in decline, up from five in 2005.
2009: U.S. government will set aside 200,541 square miles in Alaska and off its coast as "critical habitat" for polar bears.
Threats to survival
Natives of the Arctic hunt the bear for its fat and fur. Canada also
allows non-residents to hunt Polar Bears if they are guided by Inuit
hunters traveling by dog team.
Sport and commercial hunting increased in twentieth century.
Fortunately, in recent years the demand for Polar Bear skins as vanity
hangings and floor coverings has been declining. (Pelts now sell for
$400-$500. Previously a prime pelt brought $3,000)
Habitat alteration / disturbance of den sites: ongoing oil and gas
exploration and development, tourism, scientific research,
recreational activity (all-terrain vehicles, aircraft boats).
Possible oil spills (oil decomposes slowly and is highly toxic to Polar Bears when ingested through grooming or contamination of food source).
Environmental pollution. As a carnivore at the top of the Arctic food
chain, the Polar Bear is threatened by the concentration of toxic
substances in its organs (heavy metals and chlorinated hydrocarbons
have been showing up in increasing amounts in tissue samples.)
Climate warming. In southern limits of their range, population is
already forced to fast for approximately 4 months when sea ice melts.
Extension of ice-free period will increase nutritional stress on
bears and affect reproductive success and survival rates. (Stirling et al 2008)
(Molnar et al 2010)
Sea ice is breaking up at progressively earlier dates
Female body weights and numbers of independent yearlings have declined as sea ice melts
Intervals between reproduction have increased
A tipping point in polar bear survival is predicted between having to fast for 4 months and 6 months due to climate warming:
Summer fasting for 4 months = 3-6 % of adult males die of starvation
Fasting for up to 6 months = 28-48% of adult males die
Polar Bear International - Organization promoting conservation of Polar Bears and their habitat through research and education. Website has video library with interviews of bear researchers, web cams of bear activity, youth bear camps.
Arctic Research Consortium of the U.S. (ARCUS) - Nonprofit group for supporting educational and scientific efforts to share and conduct arctic research. See especially a presentation by Polar Bear researcher Ian Stirling at ARCUS' 2004 annual meeting [PDF]
The Federal Register -- website has a complete status review of Polar Bears, including Intergovernmental Panel on Climate Change (IPCC) climate studies regarding sea ice, plus Polar Bear biology and ecology.
The Integrated Taxonomic Information System (ITIS) -- Website partnership of U.S., Canadian and Mexican agencies, other organizations and specialists, Species 2000 Catalogue of Life (CoL), and the Global Biodiversity Information Facility (GBIF). The CoL and ITIS also cooperate to provide a "taxonomic backbone" to the Encyclopedia of Life (EOL project).