We are additionally asking the public for specific information concerning potential denning habitat for the polar bears along the west coast of Alaska from Barrow southward to the Seward Peninsula. These specific questions and discussion are found in the Criteria Used To Identify Critical Habitat section of this proposed rule under the discussion of terrestrial denning habitat criteria.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the ADDRESSES section.

If you submit a comment via http://www.regulations.gov, your entire commentincluding any personal identifying informationwill be posted on the website. If you submit a hardcopy comment that includes personal identifying information, you may request at the top of your document [[Page 56059]]
that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy comments on http://www.regulations.gov.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on http://www.regulations.gov, or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Marine Mammals Management Office (see FOR FURTHER INFORMATION CONTACT).

Background

On May 15, 2008 (73 FR 28212), the final rule listing the polar bear as a threatened species under the Act was published in the Federal Register. In that final rule, we made our determination on the status of the species under the Act. On the basis of a review of the best available science and commercial information related to polar bear biology, ecology, and threats, including climate change, as discussed in the final listing rule, we determined the polar bear to meet the definition of a threatened species under the Act. Please refer to our final listing rule for a more detail discussion of the biology of the species, threats to it and its habitat, and a discussion of the effects of climate change on its habitat. When a species is listed as threatened or endangered, we are to propose critical habitat for the species to the maximum extent prudent and determinable based on the best available scientific data. In our final listing rule, we determined that the designation of critical habitat was prudent, but not determinable at that time. We have since determined that critical habitat is determinable and are proposing its designation in this rule. In this proposed rule, it is our intent to discuss only those topics directly relevant to the designation of critical habitat. Information on polar bear biology and ecology that is directly relevant to designation of critical habitat is discussed under the Primary Constituent Elements section below.

General Overview

Polar bears are distributed throughout the icecovered waters of the circumpolar Arctic (Stirling 1988, p. 61). However, in accordance with the regulations at 50 CFR 424.12(h), we do not designate critical habitat within foreign countries or in other areas outside of United States jurisdiction. In the United States, polar bears occur in Alaska and adjacent State, Territorial, and U.S. waters. Therefore, these are the only areas we considered including in this proposed critical habitat designation.

Delineation of critical habitat requires, within the geographical area occupied by the polar bear, identification of the physical and biological features essential to the conservation of the species that may require special management or protection. In general terms, physical and biological features essential to the conservation of the polar bear include: (1) Annual and perennial marine seaice habitats that serve as a platform for hunting, feeding, traveling, resting, and (to a limited extent) denning; and (2) terrestrial habitats used by polar bears for denning and reproduction, as well as for seasonal use in traveling or resting. The most important polar bear life functions that occur in these habitats are feeding and reproduction. Adult female polar bears are the most important reproductive cohort in the population.

Polar bears live in an extremely dynamic seaice environment. Much of polar bear range in the United States includes two major categories of sea ice: landfast ice and pack ice. When we refer to seaice habitat in this proposed rule, we are referring to both these types of ice. Landfast ice is either frozen to land or to the benthos (bottom of the sea) and is relatively immobile throughout the winter. Shore fast ice, a type of landfast ice also known as ``fast ice,'' is defined by the Arctic Climate Impact Assessment (2005, p. 190) as ice that grows seaward from a coast and remains stationary throughout the winter and that is typically stabilized by grounded pressure ridges at its outer edge. Pack ice consists of annual and heavier multiyear ice that is in constant motion due to winds and currents. It is located in pelagic (open ocean) areas and, unlike landfast ice, can be highly dynamic. The actions of winds, currents, and temperature result in the formation of leads (linear openings or cracks in the sea ice), pressure ridges, and ice floes of various sizes. While the composition of land fast ice is uniform, regions of pack ice can consist of various ages and thicknesses, from new ice only days old that may be several centimeters (inches) thick, to multiyear ice that has survived several years and may be more than 2 meters (6.56 feet (ft)) thick. Polar bear use of these habitats may be influenced by several factors and the interaction among these factors, including: (1) Water depth; (2) atmospheric and oceanic currents or events; (3) climate phenomena such as temperature, winds, precipitation, and snowfall; (4) proximity to the continental shelf; (5) topographic relief (which influences accumulation of snow for denning); (6) presence of undisturbed habitats; (7) secure resting areas that provide refuge from extreme weather, other bears, or humans; and (8) prey availability.

Unlike some other marine mammal species, polar bears generally do not occur at high densities in specific areas such as rookeries and haulout sites. However, some denning areas, referred to as core denning areas, have a history of higher use by polar bears. In addition, terrestrial coastal areas are experiencing increasing use by polar bears for longer durations during the fall openwater period (the season when there is a minimum amount of ice present, which occurs during the period from when the sea ice melts and retreats during the summer, to the beginning of freezeup during the fall) (Schliebe et al. 2008, p. 2).

As polar bears evolved from brown bears (Ursus arctos), they became increasingly specialized for hunting seals from the surface of the sea ice (Stirling 1974, p. 1,193; Smith 1980, p. 2,206; Stirling and [Oslash]ritsland 1995, p. 2,595). Currently, little is known about the dynamics of ice seal populations (seals that rely on sea ice for their life history functions) in the Arctic or threats to these populations. However, the status of the populations of the primary species of ice seals in the Arctic is currently being investigated by the National Oceanic and Atmospheric Administration, National Marine Fisheries Service. We do know, however, that polar bears require sea ice as a platform from which to search for and hunt these seals. Polar bear movements are influenced by the accessibility of seals, their primary prey. The formation and movement patterns of sea ice strongly influence the distribution and accessibility of ringed seals (Phoca hispida), the main prey for polar bears, and bearded seals (Erignathus barbatus), a lessused prey species. When the annual sea ice begins to form in the shallower water over the continental shelf, polar bears that had retreated north of the continental shelf during the summer return to the shallower shelf waters where seal densities are higher (Durner et al. 2009a, p. 55). During the winter period, when energetic demands are the greatest, nearshore lead systems and ephemeral (may close during the winter) or recurrent (open throughout the winter) polynyas (areas of open sea surrounded by sea ice) are important for seals, and are thus important foraging habitat for polar bears. During the spring period, nearshore lead systems continue to be important hunting and foraging habitat for polar bears. The shorefast ice zone,
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where ringed seals construct subnivean (in or under the snow) birth lairs for pupping, is also an important foraging habitat during the spring (Stirling et al. 1993, p. 20). Polar bears in the southern Beaufort Sea reach their peak weights during the fall and early winter period (Durner and Amstrup 1996, p. 483). Thus, availability and accessibility of prey during this time may be critical for survival through the winter.

In northern Alaska, denning habitat is more diffuse than in other areas where highdensity denning by polar bears has been identified (Amstrup 2003, p. 595). In Alaska, certain areas, such as barrier islands (linear features of lowelevation land adjacent to the main coastline that are separated from the mainland by bodies of water), river bank drainages, much of the North Slope coastal plain, and coastal bluffs that occur at the interface of mainland and marine habitat, receive proportionally greater use for denning than other areas (Durner et al. 2003; Durner et al. 2006a). Snow cover, both on land and on sea ice, is an important component of polar bear habitat in that it provides insulation and cover for polar bear dens (Durner et al. 2003, p. 60). Geographic areas containing physical features suitable for snow accumulation and denning by polar bears have been delineated on the North Slope for an area from the Colville River Delta at Prudhoe Bay, Alaska, to the Canadian border (Durner et al. 2001, p. 119; Durner et al. 2003, p. 60).

Description and Taxonomy

Polar bears are the largest of the living bear species (Demaster and Stirling 1981, p. 1; Stirling and Derocher 1990, p. 190) and are the only bear species that is evolutionarily adapted to the arctic sea ice and marine habitat. Using movement patterns, tag returns from harvested animals, and, to a lesser degree, genetic analysis, Aars et al. (2006, pp. 3347) determined that polar bears occur in 19 relatively discrete populations. Genetic analyses have reinforced the observed boundaries between some designated populations (Paetkau et al. 1999, p. 1,571; Amstrup 2003, p. 590), while confirming overlap among others (Paetkau et al. 1999, p. 1,571; Amstrup et al. 2004a, p. 676; Amstrup et al. 2005, p. 252; Cronin et al. 2006, p. 656). Currently, there are two polar bear populations in the United States as defined under the Marine Mammal Protection Act (MMPA): the southern Beaufort Sea population, which extends into Canada; and the Chukchi and Bering Seas population, which extends into the Russian Federation (Russia) (Figure 1) (Amstrup et al. 2004a, p. 670). Although the two U.S. populations are not distinguishable genetically (Paetkau et al. 1999, p. 1576; Cronin et al. 2006, p. 658), the population boundaries are thought to be ecologically meaningful and distinct enough to be used for management. The Service listed the polar bear as a threatened species throughout the Arctic under the Act on May 15, 2008 (73 FR 28212; final rule available at http://alaska.fws.gov/fisheries/mmm/ polarbear/issues.htm).
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Figure 1. Approximate bounds (95 percent contour) for the southern Beaufort Sea and the Chukchi and Bering Seas populations based on satellite radiotelemetry locations from 19852003.

Polar bears are characterized by large body size, a stocky form, and fur color that varies from white to yellow. They are sexually dimorphic; females weigh 181 to 317 kilograms (kg) (400 to 700 pounds (lbs)), and males weigh up to 654 kg (1,440 lbs). Polar bears have a longer neck and a proportionally smaller head than other members of the bear family (Ursidae), and are missing the distinct shoulder hump common to brown bears. The nose, lips, and skin of polar bears are black (Demaster and Stirling 1981, p. 1; Amstrup 2003, p. 588).

Polar bears evolved in seaice habitats for over 200,000 years and as a result are evolutionarily adapted to this environment (Talbot and Shields, 1996, p. 490). Adaptations unique to polar bears include: (1) white pelage with waterrepellent guard hairs and dense underfur; (2) a short, furred snout; (3) small ears with reduced surface area; (4) teeth specialized for a carnivorous rather than an omnivorous diet; and (5) feet with tiny papillae on the underside, which increase traction on ice (Stirling 1988, p. 24). Additional adaptations include large, paddlelike feet (Stirling 1988, p. 24), and claws that are shorter [[Page 56062]]
and more strongly curved than those of brown bears, and larger and heavier than those of black bears (Ursus americanus) (Amstrup 2003, p. 589).

Distribution and Habitat

Polar bears are distributed throughout the icecovered waters of the circumpolar Arctic (Stirling 1988, p. 61), and rely on sea ice as their primary habitat (Lentfer 1972, p. 169; Stirling and Lunn 1997, pp. 169170; Amstrup 2003, p. 587). The distribution and movements of polar bears in the United States are closely tied to the seasonal dynamics of sea ice extent as it retreats northward during summer melt and advances southward during autumn freeze. The southern Beaufort Sea population occurs south of Banks Island and east of the Baille Islands, Canada, and ranges west to Point Hope, Alaska, and includes the coastline of Northern Alaska and Canada up to approximately 40 km (25 mi) inland (Figure 1). The Chukchi and Bering Seas population is widely distributed on the sea ice in the Chukchi Sea and northern Bering Sea and adjacent coastal areas in Alaska and Russia. The eastern boundary of the Chukchi and Bering Seas population is near Colville Delta (Arthur et al. 1996, p. 219; Amstrup et al. 2004a, p. 254), and the western boundary is near Chauniskaya Bay in the Eastern Siberian Sea. The boundary between the Eastern Siberian Sea population and the Chukchi and Bering Seas population was determined from movements of adult female polar bears captured in the Bering and Chukchi Seas region (Garner et al. 1990, p. 222) (Figure 1). The Chukchi and Bering Seas population extends into the Bering Sea, and its southern boundary is determined by the annual extent of pack ice (Garner et al. 1990, p. 224; Garner et al. 1994, p. 113; Amstrup et al. 2004a, p. 670). Historically polar bears have ranged as far south as St. Matthew Island (Hanna 1920, pp. 121122) and the Pribilof Islands (Ray 1971, p. 13) in the Bering Sea. Adult female polar bears captured in the Beaufort Sea may make seasonal movements into the Chukchi Sea in an area of overlap located between Point Hope and Colville Delta, centered near Point Lay (Amstrup et al. 2002, p. 114; Amstrup et al. 2005, p. 254). Distributions based on satellite radiotelemetry data show zones of overlap between the Chukchi and Bering Seas population and the southern Beaufort Sea population (Amstrup et al. 2004a, p. 670; Amstrup et al. 2005, p. 253). Telemetry data indicate that polar bears marked in the Beaufort Sea spend about 25 percent of their time in the northeastern Chukchi Sea, whereas females captured in the Chukchi Sea spend only 6 percent of their time in the Beaufort Sea (Amstrup 1995, pp. 7273). Average activity areas of females in the Chukchi and Bering Seas population (244,463 km\2\, range 144,659351,369 km\2\ (94,387 mi\2\, range 55,852135,664 mi\2\)) (Garner et al. 1990, p. 222) were more extensive than those in the Beaufort Sea population (166,694 km\2\, range 14,440616,800 km\2\ (64,360 mi\2\, range 21,56452,380 mi\2\)) (Amstrup et al. 2000b, p. 960). Radiocollared adult females of the Chukchi and Bering Seas population (n = 20) spent 68 percent of their time in the Russian region and 32 percent in the American region (Garner et al. 1990, p. 224).

SeaIce Habitat

Polar bears depend on sea ice for a number of purposes, including as a platform from which to hunt and feed upon seals; as habitat on which to seek mates and breed; as a platform on which to travel to terrestrial maternity denning areas, and sometimes for maternity denning; and as a substrate on which to make longdistance movements (Stirling and Derocher 1993, p. 241). Mauritzen et al. (2003b, p. 123) indicated that habitat use by polar bears during certain seasons may involve a tradeoff between selecting habitats with abundant prey availability versus the use of safer retreat habitats of higher ice concentrations with less prey. Their findings indicate that polar bear distribution may not be solely a reflection of prey availability, but that other factors such as energetic costs or risk may be involved.

Polar bears show a preference for certain seaice stages, concentrations, deformation, and forms (Stirling et al. 1993, pp. 18 22; Arthur et al. 1996, p. 223; Ferguson et al. 2000b, pp. 770771; Mauritzen et al. 2001, p. 1,711; Durner et al. 2004, pp. 1620; Durner et al. 2009a, pp. 5153). Using visual observations of bears or bear tracks, Stirling et al. (1993, p. 15) defined seven types of seaice habitat and determined habitat preferences. They suggested that the following are features that influenced polar bear distribution: (1) Stable shorefast ice with drifts; (2) stable shorefast ice without drifts; (3) floe edge ice; (4) moving ice; (5) continuous stable pressure ridges; (6) coastal low level pressure ridges; and (7) fiords and bays. Polar bears preferred the floe ice edge, stable shorefast ice with drifts, and moving ice (Stirling 1990 p. 226; Stirling et al. 1993, p. 18). In another assessment, categories of seaice habitat included pack ice, shorefast ice, transition zone (also known as the shear zone the active area consisting of openings between the shore fast ice and drifting pack ice), polynyas, and leads (USFWS 1995, p. 9).

Pack ice is the primary summer habitat for polar bears in the United States (Durner et al. 2004, pp. 1620). Shorefast ice is used by polar bears for feeding on seal pups, for movement, and occasionally for maternity denning (Stirling et al. 1993, p. 20). In protected bays and lagoons, the shorefast ice typically forms in the fall and remains stationary throughout the winter. Along the openshorelines, the shore fast ice consists of sea ice that freezes and eventually becomes grounded to the bottom, or develops from offshore ice that is pushed against the land by the wind and ocean currents (Lentfer 1972, p. 165). The shorefast ice usually occurs in a narrow belt along the coast. Most shorefast ice melts in the summer.

Open water at leads and polynyas attracts seals and other marine mammals and provides preferred hunting habitats during winter and spring. The shore system of leads and recurrent polynyas are productive areas and are kept at least partially open during the winter and spring by ocean currents and winds. The width of the leads ranges from several meters to tens of kilometers (Stirling et al. 1993, p. 17).

Polar bears must move throughout the year to adjust to the changing distribution of sea ice and seals (Stirling 1988, p. 63; USFWS 1995, p. 4). Although polar bears are generally limited to areas where the sea is icecovered for much of the year, they are not evenly distributed throughout their range on sea ice. They show a preference for certain seaice stages and concentrations, and for specific seaice features (Stirling et al. 1993, pp. 1822; Arthur et al. 1996, p. 223; Ferguson et al. 2000a, p. 1,125; Ferguson et al. 2000b, pp. 770771; Mauritzen et al. 2001, p. 1,711; Durner et al. 2004, pp. 1819; Durner et al. 2006a, pp. 3435; Durner et al. 2009a, pp. 5153). Seaice habitat quality varies temporally as well as geographically (Ferguson et al. 1997, p. 1,592; Ferguson et al. 1998, pp. 1,0881,089; Ferguson et al. 2000a, p. 1,124; Ferguson et al. 2000b, pp. 770771; Amstrup et al. 2000b, p. 962). Polar bears show a preference for sea ice located over and near the continental shelf (Derocher et al. 2004, p. 164; Durner et al. 2004, pp. 1819; Durner et al. 2009a, p. 55). This is likely due to higher biological productivity in these areas (Dunton et al. 2005, pp. 3,4673,468), and greater accessibility to prey in nearshore shear zones and polynyas compared to deepwater regions in the central polar basin (Stirling 1997, pp. 1214). Bears are most abundant near [[Page 56063]]
the shore in shallowwater areas, and also in other areas where currents and ocean upwelling increase marine productivity and serve to keep the ice cover from becoming too consolidated in winter (Stirling and Smith 1975, p. 132; Stirling et al. 1981, p. 49; Amstrup and DeMaster 1988, p. 44; Stirling 1990, pp. 226227; Stirling and [Oslash]ritsland 1995, p. 2,607; Amstrup et al. 2000b, p. 960). Durner et al. (2004, pp. 1819; Durner et al. 2009a, pp. 5152) found that polar bears in the Arctic Basin prefer sea ice concentrations (percent of ocean surface area covered by ice) greater than 50 percent, and located over continental shelf water, which in Alaska is at depths of 300 m (984.2 ft) or less.

Over most of their range, polar bears remain on the sea ice year round or spend only short periods on land. In the Chukchi Sea and Beaufort Sea areas of Alaska and northwestern Canada, for example, less than 10 percent of the polar bear locations obtained via radio telemetry were on land (Amstrup 2000, p. 137; Amstrup, USGS, unpublished data); the majority of land locations were of polar bears occupying maternal dens during the winter. However, some polar bear populations occur in seasonally icefree environments and use land habitats for varying portions of the year.

Polar bear distribution in most areas varies seasonally with the extent of seaice cover and availability of prey (Stirling and Lunn 1997, p. 178). The seasonal movement patterns of polar bears emphasize the role of sea ice in their life cycle. During the winter in Alaska, sea ice may extend 400 kilometers km (248 mi) south of the Bering Strait, and polar bears will extend their range to the southernmost proximity of the ice (Ray 1971, p. 13). Sea ice disappears from the Bering Sea and is greatly reduced in the Chukchi Sea in the summer, and polar bears occupying these areas move as much as 1,000 km (621 mi) to stay with the retreating pack ice (Garner et al. 1990, p. 222; Garner et al. 1994, pp. 407408). Throughout the Polar Basin during the summer, polar bears generally concentrate along the edge of or into the adjacent persistent pack ice (Durner et al. 2004; Durner et al. 2006a). Major northerly and southerly movements of polar bears appear to depend on distribution of sea ice delimited by the seasonal melting and refreezing of sea ice (Amstrup 2000, p. 142).

In areas where seaice cover and character are seasonally dynamic, a large multiyear home range, of which only a portion may be used in any one season or year, is an important part of the polar bear life history strategy. In other regions, where ice is less dynamic, home ranges are smaller and less variable (Ferguson et al. 2001, pp. 5152). Data from telemetry studies of adult female polar bears show that they do not wander aimlessly on the ice, nor are they carried passively with the ocean currents as previously thought (Pedersen 1945 cited in Amstrup 2003, p. 587; Amstrup et al. 2000b, p. 956; Mauritzen et al. 2001, p. 1704, Mauritzen et al. 2003a, p. 111; Mauritzen et al. 2003b, p. 123). Results show strong fidelity to activity areas that are used over multiple years (Ferguson et al. 1997, p. 1,589). Not all geographic areas within an individual polar bear's home range are used each year. The distribution patterns of some polar bear populations during the open water and early fall seasons have changed in recent years (Durner et al. 2006, p. 30; Durner et al. 2009a, pp. 49, 53). In the Beaufort Sea, for example, greater numbers of polar bears are being found on shore during the fall than recorded at any previous time (Schliebe et al. 2006, p. 559).

Terrestrial Denning Habitat

Unlike brown bears and black bears, which hibernate in winter when food is unavailable, polar bears are able to forage for seals throughout the winter (Amstrup 2003, p. 593). Generally, only pregnant polar bears routinely enter dens in the fall for extended periods (however, see Messier et al. 1994 and Ferguson et al. 2000a). Typically, pregnant female polar bears go into the dens in November, give birth in late December, and emerge from their dens after the cubs have reached 9.111.4 kg (2025 lbs) in March and April (Ramsay and Stirling 1988, p. 602). In Alaska, cubs stay with their mother for 2 years after departing the den (Amstrup 2003, p. 599).

Polar bears are particularly vulnerable to anthropogenic and natural disturbances during denning compared to other times in their life cycle (Amstrup 2003, p. 606) because they are more limited in their ability to safely move away from the disturbance. The cubs, which are born in midwinter, weigh only 600700g (1.31.5 lbs), are blind, lightly furred, and helpless (Blix and Lentfer 1979, p. R67). The maternal den provides a relatively warm, protected, and stable environment until they are large enough (approximately 11.4 kg (25 lbs)) to survive conditions outside the den in March or April. The dens provide thermal insulation, and if the family group abandons the den early, the cubs will die (Blix and Lentfer 1979, p. R67; Amstrup and Gardner 1994, p. 7). Throughout the species' range, most pregnant female polar bears excavate dens in snow located on land in the fall and early winter period (Harington 1968, p. 6; Lentfer and Hensel 1980, p. 102; Ramsay and Stirling 1990, p. 233; Amstrup and Gardner 1994, p. 5). The only known exceptions are in western and southern Hudson Bay, where polar bears first excavate earthen dens and later reposition into adjacent snow drifts (Jonkel et al. 1972, p. 146; Ramsay and Stirling 1990, p. 233), and in the southern Beaufort Sea, where a portion of the population dens in snow caves located on the drifting pack ice and shorefast ice (Amstrup and Gardner 1994, p. 5). Successful denning by polar bears requires accumulation of sufficient snow for den construction and maintenance and insulation for the female and cubs. Adequate and timely snowfall combined with winds that cause snow accumulation leeward of requisite topographic features create denning habitat (Harington 1968, p. 12). In addition, for bears moving from the sea ice to land, the timing of freezeup and the distance from the pack ice are two factors that can affect when pregnant females enter dens.

A great amount of polar bear denning arcticwide occurs in core areas, which show high use over time (Harington 1968, pp. 78). Examples include the west coast of Hudson Bay in Canada and Wrangel Island in Russia (Harrington 1968, p. 8; Ramsey and Stirling 1990, p. 233). In some portions of the species' range, polar bear dens are more dispersed, with dens scattered over larger areas at lower density (Lentfer and Hensel 1980, p. 102; Stirling and Andriashek 1992, p. 363; Amstrup 1993, p. 247; Amstrup and Gardner 1994, p. 5; Messier et al. 1994, p. 425; Born 1995, p. 84; Ferguson et al. 2000a, p. 1125; Durner et al. 2001, p. 117; Durner et al. 2003, p. 57). In northern Alaska, while denning habitat is more diffuse than in other areas, certain areas such as barrier islands, river banks, much of the North Slope coastal plain, and coastal bluffs that occur at the interface of mainland and marine habitat receive proportionally greater use for denning (Durner et al. 2004, entire; Durner et al. 2006a, entire).

The primary denning habitat for polar bears in the southern Beaufort Sea population is on the relatively flat topography of the coastal area on the North Slope of Alaska and the pack ice (Amstrup 1993, p. 247; Amstrup and Gardner 1994, p. 7; Durner et al. 2001, p. 119; Durner et al. 2003, p. 61; Fischbach et al. 2007, p. 1,400). Some of the habitat suitable for the accumulation
[[Page 56064]]
of snow and use for denning has been mapped on the North Slope (Durner et al. 2001, entire; Durner et al. 2006a, entire). The primary denning areas for the Chukchi and Bering Seas population occur on Wrangel Island, Russia, where up to 200 bears per year have denned annually, and the northeastern coast of the Chukotka Peninsula, Russia (Stishov 1991a, p. 107; Stishov 1991b, p. 91; Ovsyanikov 2006, p.169). The key characteristic of all denning habitat is topographic features that catch snow in the autumn and early winter (Durner et al. 2003, p. 61). As in the Canadian arctic, Russia, and Svalbard, Norway (Harington 1968, p. 12; Larsen 1985, p. 322; Stishov 1991b, p. 91; Stirling and Andriashek 1992, p. 364), most polar bear dens in Alaska occur relatively near the coast along the coastal bluffs and river banks of the mainland and barrier islands and on the drifting pack ice (Amstrup and Gardner 1994, p. 5; Amstrup 2003, p. 596).

Previous Federal Actions

We listed polar bears as a threatened species under the Act on May 15, 2008 (73 FR 28212). At the time of listing, we determined that critical habitat for the polar bear was prudent, but not determinable. We concluded that given the complexity of determining which specific areas in the United States might contain physical and biological features essential to the conservation of the polar bear under rapidly changing environmental conditions, we required additional time to conduct a thorough evaluation and coordinate with species experts. Thus, we did not propose critical habitat for the polar bear at that time. The Service then issued a special rule for the polar bear under section 4(d) of the Act on December 16, 2008 (73 FR 76249). The special rule provides measures that are necessary and advisable to provide for the conservation of the polar bear.

On July 16, 2008, the Center for Biological Diversity, Natural Resources Defense Council, and, Greenpeace, Inc., filed an amended complaint against the Service for, in part, failing to designate critical habitat for the polar bear concurrently with the final listing rule [Center for Biological Diversity et al. v. Kempthorne et al., No. 082113 D.D.C. (transferred from N.D. Cal.)]. On October 7, 2008, the U.S. District Court for the Northern District of California entered an order approving a stipulated settlement of the parties. The stipulated settlement, in part, requires the Service, on or before June 30, 2010, to submit to the Federal Register a final critical habitat determination for the polar bear. Comments or information that we receive in response to this proposed rule will allow us to comply with the court order and section 4(b)(2) of the Act. For more information on previous Federal actions concerning the polar bear, refer to the final listing rule and final special rule published in the Federal Register on May 15, 2008 (73 FR 28212), and December 16, 2008 (73 FR 76249), respectively.

Critical Habitat

Critical habitat is defined in section 3 of the Act as: (1) The specific areas within the geographical area occupied by a species, at the time it is listed in accordance with the Act, on which are found those physical or biological features
(a) essential to the conservation of the species and
(b) which may require special management considerations or protection; and
(2) specific areas outside the geographical area occupied by a species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means the use of all methods and procedures that are necessary to bring any endangered species or threatened species to the point at which the measures provided under the Act are no longer necessary.

Critical habitat receives protection under section 7 of the Act through the prohibition against Federal agencies carrying out, funding, or authorizing the destruction or adverse modification of critical habitat. Section 7 of the Act requires consultation on Federal actions that may affect critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area, nor does it allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by the landowner. Where the landowner seeks or requests Federal agency funding or authorization that may affect a listed species or critical habitat, the consultation requirements of section 7 of the Act would apply. However, even in the event of destruction or an adverse modification finding, the landowner's obligation is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

For inclusion in a critical habitat designation, habitat within the geographical area occupied by the species at the time it was listed must contain the physical and biological features essential to the conservation of the species. Critical habitat designations identify, to the extent known using the best scientific data available, habitat areas that provide essential life cycle needs of the species (areas on which are found the primary constituent elements, as defined at 50 CFR 424.12(b)). Occupied habitat that contains the features essential to the conservation of the species meets the definition of critical habitat only if those features may require special management considerations or protection. Under the Act, we can designate unoccupied areas as critical habitat only when we determine that the best available scientific data demonstrate that the designation of that area is essential to the conservation needs of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific data available. Further, our Policy on Information Standards under the Endangered Species Act (published in the Federal Register on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106554; H.R. 5658)), and our associated Information Quality Guidelines provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be proposed as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include articles in peerreviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, or other unpublished materials and expert opinion.

Habitat is often dynamic, and species may move from one area to another over time. Furthermore, we recognize that this critical habitat determination may not include all of the habitat areas that we may eventually determine, based on scientific data not now available to the Service, are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may
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not be required for the conservation or survival of the species.

Areas that support polar bear populations in the United States, but are outside the critical habitat designation, will continue to be subject to conservation actions we implement under section 7(a)(1) of the Act and our other wildlife authorities. They are also subject to the regulatory protections afforded by the section 7(a)(2) jeopardy standard, as determined on the basis of the best available scientific information at the time of the agency action. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may result in jeopardy findings in some cases. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCP), or other species conservation planning efforts if new information available to these planning efforts calls for a different outcome.

Methods

As required by section 4(b) of the Act, we used the best scientific data available to determine the specific geographical areas occupied at the time of listing that contain features essential to the conservation of the polar bear in the United States that may require special management or protection, and specific areas outside the geographical area occupied by the polar bear at the time of listing that are essential to the conservation of the polar bears in the United States. In proposing critical habitat for polar bears in the United States, we reviewed the relevant information available, including peerreviewed journal articles, the final listing rule, and unpublished reports and materials (such as survey results and expert opinions). In general, polar bears occupy the vast majority of their historic range. Exceptions include St. Matthew Island (Hanna 1920, pp. 121122) and the Pribilof Islands (Ray 1971, p. 13) in the Bering Sea. As described in detail below, we have proposed to designate as critical habitat only those areas currently occupied by the polar bear and have determined that designating only occupied areas as critical habitat for polar bears is sufficient for the conservation of the species in the United States. As such, we are not proposing to designate as critical habitat any areas outside the geographical area occupied by polar bears in the United States.

While the amount of information regarding important polar bear life functions and habitats associated with these functions has expanded greatly in Alaska during the past 20 years, the identification of specific physical and biological features essential to the conservation of the polar bear is complex. (see the polar bear final listing rule (May 15, 2008 (73 FR 28212) for a review of polar bear biology, ecology, and threats). Moreover, the future values of these essential features to the conservation of the species may change in a rapidly changing environment. Most notably, arctic sea ice provides a platform for critical lifehistory functions, including hunting, feeding, travel, and nurturing cubs. Sea ice is projected to be significantly reduced within the next 45 years, and some predictive climate models project complete absence of sea ice during summer months in shorter timeframes (Amstrup et al. 2008, p. 239; Durner et al. 2009a, p. 45). (see the polar bear final listing rule (May 15, 2008 (73 FR 28212)) for a more detailed discussion of climate change in the Arctic and the threat of this change to polar bears).

Primary Constituent Elements

In accordance with section 3(5)(A)(i) of the Act and the regulations at 50 CFR 424.12, in determining which specific geographical areas occupied at the time of listing to propose as critical habitat, we considered areas containing the physical and biological features essential to the conservation of the species which may require special management considerations or protection. These features include, but are not limited to:
(1) Space for individual and population growth and for normal behavior;
(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;
(3) Cover or shelter;
(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and
(5) Habitats that are protected from disturbance or are representative of the historic, geographical, and ecological distributions of a species.

We derive the specific primary constituent elements (PCEs) for the polar bear in the United States based on its physical and biological needs, as described in the Background section of this proposed rule and the following information.
Space for Individual and Population Growth and for Normal Behavior

Although home ranges can vary greatly among individuals (Garner et al. 1990, p. 224; Amstrup et al. 2000b, p. 956), the overall home range size for polar bears from the two U.S. populations is relatively large. The movement patterns and home ranges of polar bears are directly related to the seasonal, highly dynamic, redistributions of sea ice (Garner et al. 1990, p. 224; Garner et al. 1994, pp. 112113; Ferguson et al. 2001, pp. 5152; Mauritzen et al. 2001, p. 1709; Durner et al. 2004, pp. 1620; Durner et al. 2006a, pp. 2730). The movement patterns of the sea ice strongly influence the availability and accessibility of the preferred prey for polar bears, ringed and bearded seals (Stirling et al. 1993, p. 21).

Polar bears require sea ice as a platform for hunting and feeding on seals, seasonal and longdistance movements, travel to terrestrial maternal denning areas, resting, and mating (Stirling and Derocher 1993, p. 241). Moore and Huntington (2009, p. S159) classified polar bears as an iceobligate (ice restricted) species due to this dependence on sea ice as a platform for resting, breeding, and foraging. A majority of the polar bears in the U.S. populations remain with the sea ice yearround and prefer the annual sea ice located over the continental shelf, and areas near the southern ice edge, for foraging (Laidre et al. 2008, p. S105; Durner et al. 2009a, p. 39). Open water is not considered an essential feature for polar bears, because life functions such as feeding, reproduction, or resting do not occur in open water. However, open water is a fundamental part of the marine system that supports seal species, the principal prey of polar bears, and seasonally refreezes to form the ice needed by the bears. The interface of open water and sea ice is an important habitat used by polar bears (Stirling et al. 1993, pp.18, 2022; Stirling 1997, pp. 11, 15, 16; Durner et al. 2009a, p. 52). In addition, the extent of open water may play an integral role in the behavior patterns of polar bears because vast areas of open water may limit a bear's ability to access sea ice or land (Monnett and Gleason 2006, p. 5).

The optimal seaice habitat for polar bears varies both geographically and temporally, and the use of this area varies seasonally, with the greatest movements occurring during the advance of the sea ice in fall and early winter and retreat of the sea ice during spring and early summer. The dynamic nature of the sea ice in the Beaufort and Chukchi Seas, which changes continually within and among years, makes it difficult to predict the specific time or area where the optimal habitat occurs. However, the Resource Selection Function (RSF) models (Durner et al.
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2004, pp. 1619; Durner et al. 2006a, pp. 2629; Durner et al. 2009a, p. 39) show that polar bears will select areas of seaice habitat with the following characteristics: sea ice concentrations approximately 50 percent or greater that are adjacent to open water areas, flaw zones, leads, and polynyas, and that are over the shallower, more productive waters over the continental shelf (waters 300 m (984.2 ft) or less in depth).

Information on the seasonal movements of polar bears suggests that they select for ice conditions that maximize their foraging opportunities. Water depth, sea ice concentration (as described below), and proximity to the ice edge, where flaw zones, polynyas, leads, or open water occur, appear to be the important characteristics of the preferred polar bear feeding and movement habitat (Durner et al. 2004, p. 16). Preferred polar bear foraging habitat occurs primarily on the annual sea ice over the shallower (300 m (984.2 ft) or less) waters of the continental shelf (Durner et al. 2004a, p. 19; Durner et al. 2009a, p. 52). This is consistent with the distribution of their preferred prey species, ringed and bearded seals, which are also generally found over the continental shelf. Stirling et al. (1982, p. 14) found that ringed seal densities were greatest in ocean waters at depths between 50100 m (164328 ft) and with greater than 80 percent ice cover, whereas bearded seals were generally found in shallower waters (2550 m (82164 ft) deep) with relatively low ice cover.

Mauritzen et al. (2003b, p. 123) suggested that polar bears select habitat with sea ice concentrations that are optimal for hunting seals, provide safety from ocean storms, and prevent them from becoming separated from the main pack ice. Polar bears are most often found where sea ice concentrations exceed 50 percent (Stirling et al. 1999, p. 295; Durner et al. 2004, pp. 1819; Durner et al. 2006a, p. 24; Durner et al. 2009a, p. 51). However, they will use lower sea ice concentrations if this is the only ice that is available over the shallower, more productive waters of the continental shelf. This was evident during the latesummer to earlyfall open water period in August and September of 2008. During this time, most of the sea ice in the Beaufort Sea had receded beyond the edge of the continental shelf, except for a narrow tongue of sparse ice that extended over shelf waters in the eastern Beaufort Sea. Polar bears were documented using this marginal seaice habitat with sea ice concentrations between 15 percent and 30 percent, presumably in an attempt to remain in the more productive feeding areas over the continental shelf (Steve Amstrup, U.S. Geological Survey, pers. comm.; USFWS, unpublished data).

Ice in proximity to the ice edge (near open water), polynyas, or leads provide polar bears access to ringed and bearded seals. In winter, polar bears select areas of high seaice concentrations along the Alaska coast (Durner et al. 2009a, p. 52), with their preferred habitat being seaice habitat near the flaw zones, polynyas, and shore leads that run parallel to the mainland coast of Alaska. During other times of the year, the marginal sea ice zone near the sea ice edge is the optimal feeding habitat for polar bears because access and availability of ringed seals is greatest in this zone (Durner et al. 2004, pp. 1819). This is presumably because seals are available and accessible in the adjacent flaw zones and polynyas (USFWS 1995, p. 14; Stirling 1997, p. 14) that are in the shallower, more productive waters over the continental shelf.

Reductions in sea ice negatively impact polar bears by increasing the energetic demands of movement in seeking prey, causing seasonal redistribution of substantial portions of polar bear populations into marginal ice or terrestrial habitats with fewer opportunities for feeding, and increasing the susceptibility of bears to other stressors. As the summer sea ice edge retracts to deeper, less productive Polar Basin waters, polar bears will face increasing competition for limited food resources, increasing distances to swim with increased risk of drowning, increasing interaction with humans in terrestrial or nearshore areas with negative consequences, and declining population (Amstrup et al. 2008).

Reductions in sea ice will likely reduce productivity of most ice seal species as well, result in changes in composition of seal species indigenous to some areas, and eventually result in a decrease in seal abundance (Derocher et al. 2004. pp. 167169). These changes will likely decrease availability, or the timing of availability, of seals as food for polar bears. Ringed seals will likely remain distributed in shallower, more productive southerly areas that are losing their seasonal sea ice and becoming characterized by vast expanses of open water in the springsummer and fall periods (Harwood and Stirling 1992, pp. 897898). As a result, the seals will remain unavailable as prey to polar bears during critical times of the year. These factors may, in turn, result in a steady decline in the physical condition of polar bears, which precedes populationlevel demographic declines in reproduction and survival (Stirling and Parkinson 2006, pp. 266267; Regehr et al. 2007a, pp. 26792681).

One of the expected outcomes from climate change in the Arctic is that the distance between the southern edge of the pack ice and coastal denning areas will increase during the summer. This is likely to result in an increase in use of terrestrial areas during the summer and early fall (Schliebe et al. 2008, p. 2). Should the distance become too great, it could reduce polar bears' access to, and hence the availability of, optimal feeding habitat and preferred terrestrial denning locations during critical times of the year (Bergen et al. 2007, p. 6).

Based on the best information available, the dynamic nature of sea ice habitat in the Arctic, and the preference of polar bears for sea ice habitat located over the continental shelf, we have determined that sea ice over the shallower waters of the continental shelf (waters of 300 m or less (984.2 ft or less)) is an essential physical feature for polar bears in the southern Beaufort and Chukchi and Bering Seas for feeding, rearing of offspring, and normal behavior, i.e., space for individual and population growth and for normal behavior.
Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Polar bears are carnivores that feed primarily on icedependent seals (frequently referred to as ``ice seals'') throughout their range. Their main species of prey is the ringed seal; polar bears also hunt, to a lesser extent, bearded seals (Stirling and Archibald 1977, p. 1,127; Smith 1980, p. 2, 201). In some locales, other seal species are taken. On average, an adult polar bear needs approximately 2 kg (4.4 lbs) of seal fat per day to survive (Best 1985, p. 1,035). Sufficient nutrition is critical for survival in the arctic environment and may be obtained and stored as fat when prey is abundant.

Although seals are their primary prey, polar bears occasionally take much larger animals, such as walruses (Odobenus rosmarus), narwhal (Monodon monoceros), and beluga whales (Delphinapterus leucas) (Kiliaan and Stirling 1978, p. 199; Smith 1980, p. 2,206; Smith 1985, pp. 7273; Lowry et al. 1987, p. 141; Calvert and Stirling 1990, p. 352; Smith and Sjare 1990, p. 99). In some areas and under some conditions, prey other than seals, such as carrion or remains of subsistence harvested bowhead whales, may be important to polar bear sustenance as shortterm supplemental forms of nutrition. Stirling and [Oslash]ritsland (1995, p. 2,609) suggested that in areas where
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ringed seal populations were reduced, other prey species were being substituted. For example, harp seals (Pagophilus groenlandicus) are the predominant prey species for polar bears from the Davis Strait population in Canada (Iverson et al. 2006, p. 110). Changes in the distribution of harp seals may continue to support large numbers of polar bears from the Davis Strait population even if ringed seals become less available (Stirling and Parkinson 2006, p. 270; Iverson et al. 2006, p. 110). However, the increased take of other species, such as bearded seals, walrus, and harbor seals, in the United States, if those species were available, would likely not compensate for reduced availability of ringed seals (Derocher et al. 2004, p. 168).

Polar bears are very sensitive to changes in sea ice due to climate change because of their reliance on sea ice and their specialized feeding requirements (Laidre et al. 2008, p. S112). The importance of availability of prey to polar bear reproduction was evident in the mid 1970s when a decline in ringed and bearded seals resulted in a decline in the weights of adult female polar bears and a decline in reproduction (Stirling et al. 1982, p. 19; Amstrup et al. 1986, p. 249). Changes in the distribution and abundance of optimal sea ice feeding habitat due to climate change could also affect polar bear denning success. For example, the availability and accessibility of seals to polar bears, which often hunt at the seals' breathing hole, are likely to decrease with increasing amounts of open water or fragmented ice (Derocher et al. 2004, p. 167). Pregnant polar bear females with insufficient fat stores prior to denning, or in poor hunting condition in the early spring after den emergence, may lead to increased cub mortality (Atkinson and Ramsay 1995, pp. 565566; Derocher et al. 2004, p. 170). Regehr et al. (2007b, pp. 1718) suggested that the increase in the duration of the open water period in fall was a contributing factor to the decrease in the productivity of polar bears in the southern Beaufort Sea population and to the population decline in the Western Hudson Bay population (Stirling et al. 1999, p. 304; Regehr et al. 2007a, p. 2,673). In the southern Beaufort Sea, the decline in the survival rate of cubs may be directly linked to the ability of females to obtain sufficient nutrition prior to denning (Regehr et al. 2006, p. 11, Amstrup et al. 2008, p. 236). The inability to obtain sufficient food resources may be due to increases in the length of the fall open water period, which reduces the amount of time available for feeding prior to denning. Polar bears in the southern Beaufort Sea typically reach their maximum weight in fall. Fall, therefore, may be a critical period for winter survival for this population (Garner et al. 1994, p. 117; Durner and Amstrup 1996, p. 483). In Alaska, it is not unusual for females in poor condition after den emergence to lose their cubs (Amstrup 2003, p. 601). Thus, the availability of seal pups to adult females with cubsoftheyear in the spring following den emergence may also be critical (Garner et al. 1994, p. 117; Stirling and Lunn 1997, p. 177). Atkinson and Ramsay (1995, p. 565), and Derocher and Stirling (1996, p. 1,249; 1998, pp. 255256), found that heavier cubs have a higher survival rate, and that declines in fat reserves in females during critical periods can negatively affect denning success and cub survival.

Based on the information presented above, we conclude that the accessibility and availability of sufficient food resources is dependent upon availability of suitable seaice habitat over the shallower waters of the Chukchi and Bering Seas and southern Beaufort Sea. Therefore, we have determined that sea ice that moves over the shallower waters of the continental shelf (300 m (984.2 ft) or less) is an essential physical feature for polar bears in the southern Beaufort and Chukchi and Bering Seas for feeding, rearing of offspring, and normal behavior.

Cover or Shelter

Polar bears from the U.S. populations generally remain with the sea ice for most of the year, and, except for maternal denning, only spend short periods of time on land. This may be due to the availability of the sea ice yearround and less severe weather conditions compared to more northerly latitudes. Polar bears from U.S. populations take advantage of logs, ocean bluffs, and stream and river drainages to seek shelter from the wind (Lentfer 1976, p. 9). Messier et al. (1994, p. 425), Ferguson et al. (2000a, p. 1,122) and Omi et al. (2003, p. 195) found that polar bears of all ages and both sexes from more northerly populations in Canada may remain in temporary shelter dens in snow drifts on the ice for up to 2 months, presumably to avoid storms, periods of intense cold, and food shortages. Occasionally polar bears in the United States, particularly females with small cubs, will dig temporary shelter dens to avoid severe winter storms (Lentfer 1976, p. 9; Amstrup, unpublished data). Information from native hunters in Alaska suggests that, except for parturient (bearing or about to bear young) females and females with young cubs, polar bears do not require additional cover or shelter for survival throughout the year (Lentfer 1976, p. 9). However, the importance of these shelter dens may increase in the future if polar bears, experiencing nutritional stress as a result of loss of optimal seaice habitat and access to prey, need to minimize nonessential activities to conserve energy.

Currently, cover and shelter are not considered to be limiting factors for the conservation of polar bears in the United States, except for the importance of maternal dens. The needs of parturient females and cubs for cover and shelter are satisfied through denning behavior and discussed below.
Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring

One of the most critical periods for polar bears occurs during denning because the newborn cubs are completely helpless and must remain in the maternal den for protection and growth until they are able, at approximately 3 months of age, to survive the outside climate (Blix and Lentfer 1979, p. R70; Amstrup 2003, p. 596; Durner et al. 2006b, p. 31). Den disturbances from human activities have caused den abandonment in the past (Amstrup 1993, p. 249).

The majority of polar bears that den in the United States are from the southern Beaufort Sea population. Unlike the high density of dens that occur on Wrangel Island, Russia (one of the principal denning areas of the Chukchi and Bering Seas population), the individual polar bear dens in the United States are widely dispersed over large areas of denning habitat in northern Alaska. Even though this denning habitat is expansive, barrier islands, river bank drainages, much of the North Slope coastal plain, and coastal bluffs that occur at the interface of mainland and marine habitat receive proportionally greater use for denning than other areas (Amstrup 2003, pp. 596597; Durner et al. 2006b, p. 34).

Polar bears from the southern Beaufort Sea population den on drifting pack ice, shorefast ice, and land (Amstrup and Gardner 1994, pp. 45), while most other polar bear populations den only on land or shorefast ice (Amstrup 2003, p. 596). The distribution of maternal denning in the southern Beaufort Sea appears to have changed in recent years. While Amstrup and Gardner (1994) observed that approximately 50 percent of maternal dens occurred on the pack ice, Fischbach et al. (2007, p. 1,399)
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documented a decrease in pack ice denning over 2 decades, from 62 percent (19851994) to 37 percent (19982004). Fischbach et al. (2007, p. 1,403) concluded that the changes in the den distribution were in response to delays in the autumn freezeup and a reduction in availability and quality of the more stable pack ice suitable for denning, due to increasingly thinner and less stable ice in fall. Amstrup and Gardner (1994, p. 4) noted that, in the U.S. southern Beaufort Sea population, only a small proportion (4 percent) of polar bears den on the shorefast ice adjacent to the mainland coast of Alaska. The overall occurrence of dens on sea ice in the Arctic is thought to be relatively low based on current studies using radio telemetry (Amstrup 2003, p. 596). Protection of the few pelagic dens on drifting sea ice in the Beaufort Sea is impracticable because of the large area involved, the difficulty in locating dens, and the dynamic nature of the sea ice (Garner et al. 1994, p. 116).

Polar bears in the Beaufort Sea exhibit fidelity to denning areas but not specific den sites (Amstrup and Gardner 1994, p. 7). The location of terrestrial maternal dens is dependent upon a variety of factors, such as sea ice conditions, prey availability, and weather, all of which vary seasonally and annually. Stirling and Andriashek (1992, p. 364) found that dens often occurred on land adjacent to areas that developed sea ice early in the autumn. It is expected that the number of polar bears denning on land in northern Alaska will increase, if the predictions of the continued loss of arctic sea ice due to climate change occur (Schliebe et al. 2008, p. 2).

Polar bears typically choose terrestrial den sites that are

FOR FURTHER INFORMATION CONTACT

Thomas J. Evans, Marine Mammals Management Office, U.S. Fish and Wildlife Service, 1011 East Tudor Road, Anchorage, AK 99503; telephone 907/7863800; facsimile 907/786 3816. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 8008778339.