Potential Effects of Climate-change on Polar Bear Populations in the Circumpolar Arctic

Ursus maritimus

Description

• Heavy, stout bodies with muscular legs and necks

• Males – 2.5 –3 meters in length– 775-1,500 pounds

• Females– 2-2.5 meters in length– 330-550 pounds

• Live to about 20 yrs.– In London, one lived to 41

• Look white but fur is actually pigment-free

Description…

• Only the nose and footpads are without fur

• Feet are partially webbed

– Aids in swimming

– Can swim for over 60 miles and 6 miles/hour without resting

• Can run up to 25 miles/hour for short distances

• Have sharp claws for traction on slippery ice

• Blubber can measure 4.5 inches thick

Distribution

• Circumpolar in distribution

• Always associated with sea ice

• In NA, polar bears range from Alaska on west coast to Baffin Island, and Newfoundland and Labrador on the East coast

• Distributed throughout coastal habitat and on the Arctic Sea

Distribution

Diet

• Opportunistic feeders

• Almost exclusively carnivorous

• Ring seals are primary food source, prefer fat

• Spring- ½ of ring seals killed are newborn pups, but weaned pups and post-parturient females are also killed

Diet…

• Polar bears also kill beluga whales and walruses

• Polar bears will scavenge on seal, whale, and walrus carcasses, but rarely on carcasses of terrestrial animals

• Occasionally birds, eggs, vegetation and small mammals are eaten

Diet…

• Food Chain is simple– Zooplankton feed on algae on bottom of ice– Arctic cod feed on zooplankton– Ringed seals feed on arctic cod– Polar bears feed on ringed seals– Small changes in food chain can have drastic

affects• Changes in environment

Diet…

• Can go long periods without feeding– Males usually go about

3-4 months without eating because of melting ice

– Pregnant females go without food for 8 months

• Longest among mammals

Hunting

• Bears capture seals by still hunting, stalking on land, aquatic stalking, and by stalking birth lairs.

• The type of hunting depends on the season.

Hunting…

• Still Hunting– Used year round

- Waits for the seals to surface through breathing holes

- It then bites onto the head or upper body and flips it out of the water

- This usually takes less than an hour

Hunting…

• Stalking on land– Used in summer when

seals are landed on ice

– Once a seal is spotted, a polar bear will slowly sneak towards it

– When it is within about 50 feet it charges the seal and grabs it with its claws or teeth

Hunting…

• Aquatic stalking– Used in summer when

seals haul out on ice

– Polar bear swims toward a landed seal and it grabs the seal when it reaches the ice edge

Hunting…

• Stalking birth lairs– Used in spring when

ringed seals give birth

– Birth lairs are caves built under snow drifts next to a hole

– Mother breaks through the roof and and grabs the seal

Eating habits

• Once a seal is captured, polar bears bite it several times on the head and neck

• The skin and fat are eaten first, followed by the meat

• Usually don’t eat the entire kill

Reproduction

• Polygamous• Breed from March – May on

sea ice• Several males follow 1

female (farther than 62 mi) and may result in intense fights

• Exhibit delayed implantation until September or October when female enters den

• Gestation – 8 months• 1-4 cubs, usually 2

Reproduction…

• 6 out of 10 cubs die in 1st year – Starve, predation,

accidents

• Drink mother’s milk (richest of all carnivores)

– 20 months

• Weaned at about 2-3 – Depends on location

Reproduction…

Sexual Maturity Females – 4 years Males – 6 years

Cubs Cubs usually weigh

between 0.5-1 kg Lactation lasts1.5-2.5 yrs Cubs remain with mothers

for 2-3 yrs

Denning

• Females seek out maternity dens in late August but don’t usually enter them until October

• Usually are on south facing slopes– Most are on land

• Dens are usually 2m (L) x 1.5m (W) x 1 m (H)

• Temp is usually 20 degrees F warmer inside the den

Social Structure

• Adult bears remain solitary except in breeding season

• Parental care provided by female only

• Males will often prey upon cubs and females

• Females may move into habitats with less resources to avoid cannibalism by males

Population Dynamics

• Overall species is stable, but are vulnerable to oil and gas exploration as well as humanencroachment

• As development continues in Arctic, the potential for contamination of the bears food and chances of oil spills increase greatly

• At highest trophic level, more vulnerable to accumulation of environmental toxins

Population Dynamics…

• Total population is about 22,000-27,000• 5 nations with polar bear populations

– Canada – has the most (15,000)

– Greenland

– Norway

– U.S

– Russia

– All are involved with the International Agreement for the Conservation of Polar Bears

Population Dynamics…

• Canada Polar Bears– 15,000

– Smaller in size, weigh less, and have fewer cubs

– Native hunting is allowed under the provision of the International Agreement

– Each community is given a quota• About 500 bears are harvested each year

• Natives are allowed to sell hunting rights to non-natives

Population Dynamics…

• Norway– Completely protected since 1973– Svalbard islands

• Population has rebounded from about 1000 up to 2000

– PCB levels are the main concern here• Levels are about 2 ½ to 17 times higher than in NA

Population Dynamics…

• Greenland– Natives may hunt polar bears but aren’t allowed

to sell any parts– About 100 bears are harvested annually

Population Dynamics…

• Russia– Russian natives recently allowed to hunt them– Russian economy has collapsed due to loss of

law and order• Poaching has become a major problem

– High levels of pollutants

Population Dynamics…

• U.S.(Alaska)– Hunting by natives is allowed for subsistence

• 100 harvested annually

– Restrictions• Carcasses must be used

• Not allowed to sell the skins

• Although may make and sell products from them

Mortality

• Man is only natural enemy

• Human presence in bear habitat leads to human-bear conflicts and usually result in killing of bear

• Bears may also be killed for wandering into areas of human development **Usually adult females trying to find food for dependent young

Economic Value

• Untanned pelts sell for $500-$3000– Depending on size and

quality

– Annual economic value of the hunts and hides are about $1 million in Canada

• Bear meat– Consumed by humans and

used as dog food• Bear liver – Vitamin A

Habitat

• Pack ice– Hunting platform and

protective cover

• Open water– Presence of seals

• Land– For denning, cover,

and supplemental food

How is the climate change effecting Polar Bears?

Changes in Climate

• The earth’s climate is predicted to change

• Human activities are altering the chemical composition of the atmosphere

• Buildup of greenhouse gasses

Changes in Climate

Since beginning ofindustrial revolution:

Conc. of carbon dioxide has increased by 30%

Conc. of methane have more than doubled

Conc. of nitrous oxide have increased by 15%

Changes in Climate

• Global temps are rising (land surface temp has risen .45-.6 degrees Celsius)

• Precipitation has increased by about 1% over world’s continent in the last century

• Sea level has risen 15-20 cm in the last century

Warming of Arctic climate

• The warming of the climate is due to increasing conc. of greenhouse gasses in the atmosphere

• A major concern is how this may effect ice on the Arctic Ocean

• More warming means less ice in the Arctic

What’s causing it?

• Humans are causing concern for the polar bear’s future

– Altering the global climate

• Burning fossil fuels; gasoline and coal

• Clearing large swaths of forest

• Releasing vast amounts of carbon dioxide

Effects of Arctic Climate Change

• Scientists believe the extra carbon dioxide may cause warmer temperatures

• At North and South poles it could lengthen the winters

– Longer polar winters could help create a hole in the Arctic’s ozone layer

• Melting sea ice– Keeps polar bears from main food source, ringed seals

– Ringed seals are becoming less accessible due to shorter ice season

Effects of Arctic Climate Change…

• NASA study found that a 2.9% decline per decade in total Arctic sea ice over last 20 yrs

• New Canadian study further concludes the sea ice season in western Hudson Bay has been reduced by about 3 weeks in same time period– As a result of declining sea ice the polar bears have less

time to hunt and are returning to land in poor conditions– Male and female weight is declining and females are

having fewer cubs– Hasn’t been a population decline yet, but could in the

future

Polar bears and Sea Ice

• Sea ice is essential to polar bears

• In order to hunt seals, the polar bears have to walk across the ice

• Also used for travel route to seek mates during breeding season

• Maternity denning

• Dispersal routes

Climatic effects on Polar bears as well as seals

• Less sea ice means less food for polar bears

• Less food means lower reproductive rates

• Seals are also being effected

• Seals depend on ice to give birth and nurse their pups

How are seals and bears effected?

• Polar bears having lower reproductive rates, this will cause a decrease in the population eventually

• Seals will also experience a decline in population due to loss of the platform to nurse their pups and give birth

Western Hudson Bay Polar Bears

• Here polar bears already spend 4 months of the year fasting and rely on fat reserves during the ice free period

• This is the population that scientists believe will be effected first

• Avg weights of females are lower than they were in the 1980’s

Decline in body conditionof Hudson Bay Bears

If ice break-up began to occur 2 or 3 wks earlier:

Adult females may not be able to store enough fat to produce cubs

Females may not be able to nurse cubs through the ice free period

Decline in body condition of females would cause an eventual decline in population because mortality would out weigh cub production

Decline in body condition of Hudson Bay Bears

Example:• Avg weights of female

Polar Bears were a lot lower in the later 1980s than they were in the early 1980s

• Lower cub survival and reproduction rates were noted

Hudson Bay

Climatic Effects on Denning

Fall-Multiyear pack ice

moves southOpen water between

polar pack and the coast freezes

Allows pregnant bears to reach the coast for maternity denning

Climatic Effects on Denning…

If polar pack is reducedand freezing of openwater is delayed: Females can’t reach coast

to den Will den on the multiyear

iceEx: southern Beaufort Sea

popln

Climatic Effects on Denning…

Increased probabilityOf precip. with warmingarctic:If Rain: Dens may collapse before

female and cubs have emerged(ex) Beufort sea coast, 2 cubs and mother were crushed to death from den collapsing on them

Increased Precipitation effecting ring seal birth lairs

Seals give birth in March-April If precipitation was snow,

it would benefit seal pup survival before being weaned

It precipitation was rain, it would collapse birth lairs causing predation of pups by polar bears and arctic fox

Increased Precipitation effecting ringed seal birth lairs

• Increased predation of seal pups by polar bears and arctic foxes caused by increased rainfall could lower the seal popln enough to cause a decline in polar bear poplns.

Human-Bear Interactions due to climate change

Bears are coming toshore thinner, and laterfreeze-up is causing them tostay around longer This causes them to be

nutritionally stressed and wander into Churchill in search of food

Bears are often found scavenging in Churchill’s dump

Human – Bear Interactions due to climate change…

• If ice free time gets

longer, bears will become

more nutritionally stressed

and will have to get food

wherever they can

(This could increase probability of humans being preyed upon)

Human – Bear interactions

Polar Bear Alert Program Instigated at Churchill Ensure safety to people

and protection of property from bears

Ensure safety of bears and avoid harassment and killing of bears

Nuisance Bears

Nuisance Bears or bearsentering the dump inChurchill:• Captured and held in a

holding facility • When ice freezes, the

bears are released• Some problem bears are

airlifted to wilderness 25 mi north of Churchill right away instead of being held

 

                       

Conservation Steps

• 1.) First International Scientific Meeting on the Polar Bear, 1965– Meeting set stage for international agreement on polar bear

conservation

• 2.)The International Agreement on Conservation of Polar Bears and Their habitat, 1973– 5 nations (Canada, Greenland, Norway, U.S., and Russia) agreed

to protect polar bear habitat, such as dennning, feeding areas, and migratory routes; ban hunting of bears from aircrafts and boats; conduct research and management and exchange these results

Conservation…

• 3.)United States Marine Mammal Protection Act, 1972– Polar bears are protected in U.S.(Alaska)

• Hunted only by Alaskan natives

• 4.) Convention on Int’l Trade in Endangered Species of Wild Fauna and Flora– In 1975, the polar bear was placed on Appendix II (CITES),

identified as threatened, or likely to become endangered if trade isn’t regulated. Int’l trade is permitted with proper documentation issued by the gov’t of the exporting country

• 5.)Int’l Union for the Conservation of Nature and Natural Resources/World Conservation Union– A worldwide conservation group consisted of gov’t, non-gov’t , and

independents

Management Strategies

• Research is needed– Current distribution– Habitat requirements– Food habits– Patterns of land use– Reproductive behavior– Ability to sustain a certain rate of mortality

Some solutions to the effects of the changing climate on the bearsSlow the buildup ofgreenhouse gases Use solar energy

Reduce burning of fossil fuels

Use wind power

Plant trees