Transcript Document

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 postparturient 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
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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 human
encroachment
• 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
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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 humanbear 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 of
industrial 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 condition
of 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
FallMultiyear pack ice
moves south
Open 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 reduced
and freezing of open
water is delayed:
 Females can’t reach coast
to den
 Will den on the multiyear
ice
Ex: southern Beaufort Sea
popln
Climatic Effects on Denning…
Increased probability
Of precip. with warming
arctic:
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 MarchApril
 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 to
shore thinner, and later
freeze-up is causing them to
stay 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 bears
entering the dump in
Churchill:
• 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
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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 bears
Slow the buildup of
greenhouse gases
 Use solar energy
 Reduce burning of fossil
fuels
 Use wind power
 Plant trees