Federal Register, Volume 76, Number 149, August 3, 2011, Pages 46595-47054 Page: 47,020
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47020 Federal Register/Vol. 76, No. 149/Wednesday, August 3, 2011 /Rules and Regulations
as a food source is not known. Polar
bears have also been observed
consuming non-food items including
Styrofoam, plastic, antifreeze, and
hydraulic and lubricating fluids.
Polar bears use the sea ice as a
platform to hunt seals. Polar bears often
hunt seals along leads and other areas
of open water. Polar bears also hunt
seals at breathing holes, or by breaking
through the roof of seal lairs. Lairs are
excavated by seals in snow drifts on top
of the ice. Bears also stalk seals in the
spring when they haul out on the ice in
warm weather. The relationship
between ice type and polar bear
distribution is as yet unknown, but it is
suspected to be related to seal
availability. Due to changing sea ice
conditions, the area of open water and
proportion of marginal ice has increased
and extends later in the fall. This may
limit seal availability to polar bears as
the most productive areas for seals
appear to be over the shallower waters
of the continental shelf.
Mortality
Polar bears are long-lived (up to 30
years), have no natural predators, and
do not appear prone to death by
diseases or parasites. Cannibalism by
adult males on cubs and occasionally on
adult bears is known to occur. The most
significant source of premature adult
polar bear mortality is human activity.
Before the MMPA was passed in 1972,
polar bears were taken by sport hunters
and residents. Between 1925 and 1972,
the mean reported kill was 186 bears per
year. Seventy-five percent of these were
males, as cubs and females with cubs
were protected. Since 1972, only Alaska
Natives from coastal Alaskan villages
have been allowed to hunt polar bears
for their subsistence uses, for the
manufacture of handicraft and clothing
items. From 1980 to 2005, the total
annual harvest for Alaska averaged 101
bears: 64 percent from the Chukchi Sea
and 36 percent from the Beaufort Sea.
Other sources of mortality related to
human activities include bears killed
during research activities, euthanasia of
sick or injured bears, and defense-of-life
kills by non-Natives (Brower et al.
2002).
Distribution and Abundance of Polar
Bears in the Beaufort Sea
Polar bears are dependent upon the
sea ice as a platform for foraging. The
most productive locations seem to be
areas near the ice edge, leads, or
polynyas over the continental shelf
(Durner et al. 2004). Polar bears can also
be observed throughout the year in the
onshore and nearshore environments,where they will opportunistically
scavenge on marine mammal carcasses
washed up along the shoreline
(Kalxdorff and Fischbach 1998). Their
distribution in the coastal habitat can be
influenced by the movement of the
seasonal pack ice.
More specifically, during the ice-
covered season, pregnant females can
use terrestrial denning habitat between
late-October and mid-April. The
percentage of pregnant females using
terrestrial habitat for denning is
unknown but, as stated earlier, the
proportion of dens on terrestrial habitat
has increased in recent years. In
addition, a small proportion of bears of
different cohorts may be found along the
coastline as well during this time
period. During the open water season
(July through September), a small
proportion of bears will utilize the
coastal environments while the majority
of the population will be on the ice edge
of the pack ice.
During the late summer/fall period
(August through October), polar bears
are most likely to be encountered along
the mainland coastline and barrier
islands, using these features as travel
corridors and hunting areas. Based on
Industry observations, encounter rates
are higher during the fall period (August
to October) than any other time period.
The duration the bears spend in these
coastal habitats depends on storm
events, ice conditions, and the
formation of the annual ice. In recent
years, polar bears have been observed in
larger numbers than previously
recorded during the fall period. The
remains of subsistence-harvested
bowhead whales at Cross and Barter
Islands provide a readily available food
source for the bears in these areas and
appear to play a role in these numbers
(Schliebe et al. 2006). Based on Industry
observations and coastal survey data
acquired by the Service, up to 125
individuals of the SBS bear population
have been observed during the fall
period between Barrow and the Alaska-
Canada border.
Climate Change
Habitat loss due to changes in Arctic
sea ice has been identified as the
primary cause of decline in polar bear
populations, and the decline of sea ice
is expected to continue throughout the
polar bear's range for the foreseeable
future (73 FR 28212). In support of the
listing, Amstrup et al. (2007) projected
that if current sea ice declines continue,
the sea-ice retreat may eventually
exclude bears from onshore denning
habitat in the Polar Basin Divergent
Region, where they have projected a 42
percent loss of optimal summer polarbear habitat by 2050. SBS and CS polar
bear populations inhabit this ecoregion,
and Amstrup et al. (2007) have
projected that these populations will be
extirpated within the next 45-75 years
if sea ice declines continue at current
rates.
Climate change is likely to have
serious consequences for the world-
wide population of polar bears and their
prey (ACIA 2004, Derocher et al. 2004,
NRC 2003). Climate change is expected
to impact polar bears in a variety of
ways. The timing of ice formation and
breakup will impact seal distributions
and abundance, and, consequently, how
efficiently polar bears can hunt seals.
Reductions in sea ice are expected to
increase the polar bears' energetic costs
of traveling, as moving through
fragmented sea ice and open water
requires more energy than walking
across consolidated sea ice.
Decreased sea ice extent may impact
the reproductive success of denning
polar bears. Polar bears require a stable
substrate for denning. As ice conditions
moderate, ice platforms become less
stable, and coastal dens become
vulnerable to erosion from storm surges.
In the 1990s, approximately 50 percent
of the maternal dens of the SBS polar
bear population occurred annually on
the pack ice rather than on terrestrial
sites (Amstrup and Gardner 1994).
Recently, the proportion of dens on
pack ice declined from 62 percent in
1985-1994 to 37 percent in 1998-2004
(Fischbach et al. 2007). Terrestrial
denning is expected to increase in the
future, despite the threats of coastal
erosion.
Due to the changing ice conditions,
the Service anticipates that polar bear
use of the Beaufort Sea coast will
increase during the open-water season
(June through October). Indeed, polar
bear use of coastal areas during the fall
open-water period has increased in
recent years in the Beaufort Sea. This
change in distribution has been
correlated with the distance of the pack
ice from the coast at that time of year
(the farther from shore the leading edge
of the pack ice is, the more bears are
observed onshore) (Schliebe et al. 2006).
Reductions in sea ice will result in
increased distances between the ice
edge and land, which will in turn lead
to increasing numbers of bears coming
ashore during the open-water period, or
possibly drowning in an attempt to
reach land. An increased number of
bears on land may increase human-bear
interactions or conflicts during thisperiod.
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United States. Office of the Federal Register. Federal Register, Volume 76, Number 149, August 3, 2011, Pages 46595-47054, periodical, August 3, 2011; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc52326/m1/431/?rotate=270: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.