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At least 1,801 records · Page 100Linked to original sources
USGS1991

Effects of wind-hardened snow on foraging by reindeer (Rangifer tarandus)

Various methods were investigated for assessing the relationship between wind-hardened snow ( upsik ) and forage availability to reindeer. Mean bottom area of individual craters was not a function of depth, hardness or integrated hardness. Individual crater area was partially dependent on specific cratering time (r2 = .60). Cratering time per active period increased with integrated snow hardness (r2 = .88). Number of craters and total area cratered increased with decreasing site hardness. Reindeer always cratered microsites of lesser depth and hardness than found in the general feeding site. A threefold decrease in snow hardness resulted in a fourfold increase in forage availability.

Arctic↗
USGS1983

Use of nearshore and estuarine areas by gray whales ( Eschrichtius robustus ) in the eastern Bering Sea

During spring aerial surveys of the coast of the southeastern Bering Sea significant numbers of gray whales were seen in nearshore waters along the north side of the Alaska Peninsula. Many (50-80%) of these animals were observed surfacing with mud trails or lying on their sides, characteristics both associated with feeding. A migration route close to shore (within 1-2 km) was used until whales neared Egegik Bay, where they began to head west 5-8 km offshore, across northern Bristol Bay. Smaller numbers of gray whales were present throughout summer in nearshore waters and estuaries along the north side of the Alaska Peninsula. At Nelson Lagoon gray whales normally used the lagoon in spring, were absent during early summer, returned in mid-summer, and then were present until late November when they departed for the wintering grounds. Gray whales were present in the lagoon most often during periods of peak tidal flow; those that appeared to be feeding were oriented into the current. Three behaviors that appeared to be associated with feeding were observed: side-feeding from a stationary position within shallow waters of lagoon channels, diving within the lagoon and in nearshore waters, and elliptical side-feeding in the surf zone along the outer coast. Large crustaceans of the genus Crangon were available to and probably eaten by gray whales at Nelson Lagoon.

Alaska↗
USGS2009

Post-den emergence behavior of polar bears ( Ursus maritimus ) in Northern Alaska

We observed polar bear ( Ursus maritimus ) maternity den sites on Alaska’s North Slope in March 2002 and 2003 in an effort to describe bears’ post-den emergence behavior. During 40 sessions spanning 459 h, we observed 8 adults and 14 dependent cubs outside dens for 37.5 h (8.2% of total observation time). There was no significant difference between den emergence dates in 2002 (mean = 15 Mar ± 4.1 d) and 2003 (mean = 21 Mar ± 2.1 d). Following initial den breakout, polar bears remained at their den sites for 1.5 to 14 days (mean = 8.1 ± 5.1 d). The average length of stay in dens between emergent periods was significantly shorter in 2002 (1.79 h) than in 2003 (4.82 h). While outside, adult bears were inactive 49.5% of the time, whereas cubs were inactive 13.4% of the time. We found no significant relationships between den emergence activity and weather. Adult polar bears at den sites subjected to industrial activity exhibited significantly fewer bouts of vigilance than denned bears in undisturbed areas (t = -5.5164, df = 4, p = 0.00). However, the duration of vigilance behaviors at sites near industrial activity was not significantly shorter than at the other sites studied (t = -1.8902, df = 4, p = 0.07). Results for these bears were within the range of findings in other studies of denned polar bears.

Arctic↗
USGS1981

Earth flows along Henry Creek, northern Alaska

Many earth flows occurred during the summer of 1979 in the hilly terrain near Umiat, Alaska, particularly along Henry Creek. Most were shallow, involving only the tundra mat and no more than 1.5 m of the underlying mud. The summer of 1979 was the warmest and wettest for the period of record at Umiat, and precipitation was characterized by brief but intense localized rainstorms. Failure probably was triggered by the heavy rains and facilitated by an absorbent tundra mat over a clayey substrate, and perhaps in some cases by a thicker than normal active layer. Flows of this kind have occurred repeatedly in the Umiat area, most likely during summers in which climatic conditions were similar to those of 1979.

Alaska↗
USGS1970

Summer foods of lesser scaup in subarctic taiga

Reports on the food of 25 adult and 38 juvenile Aythya affinis , collected in June-Sept 1967 along the Yellowknife Highway north of Great Slave Lake. The vegetation, physiography and ponds of the area, the collecting and statistical methods are briefly described. Approx 99% of the scaup diet was animal material; juveniles in mid-summer fed on freeswimming organisms such as Chaoborinae (phantom midges) and Conchostraca (clam shrimps); in late summer they, as did adults in June, fed on bottom organisms such as amphipods, odonates and corixids. Seeds, copepods and cladocerans were seldom or never eaten.

Northwest Territories↗
USGS2009

The annual migration cycle of emperor geese in western Alaska

Most emperor geese ( Chen canagica ) nest in a narrow coastal region of the Yukon-Kuskokwim Delta (YKD) in western Alaska, but their winter distribution extends more than 3000 km from Kodiak Island, Alaska, to the Commander Islands, Russia. We marked 53 adult female emperor geese with satellite transmitters on the YKD in 1999, 2002, and 2003 to examine whether chronology of migration or use of seasonal habitats differed among birds that wintered in different regions. Females that migrated relatively short distances (650–1010 km) between the YKD and winter sites on the south side of the Alaska Peninsula bypassed autumn staging areas on the Bering Sea coast of the Alaska Peninsula or used them for shorter periods (mean = 57 days) than birds that made longer migrations (1600–2640 km) to the western Aleutian Islands (mean = 97 days). Alaska Peninsula migrants spent more days at winter sites (mean = 172 days, 95% CI: 129–214 days) than western Aleutian Island migrants (mean = 91 days, 95% CI: 83–99 days). Birds that migrated 930–1610 km to the eastern Aleutian Islands spent intermediate intervals at fall staging (mean = 77 days) and wintering areas (mean = 108 days, 95% CI: 95–119 days). Return dates to the YKD did not differ among birds that wintered in different regions. Coastal staging areas on the Alaska Peninsula may be especially important in autumn to prepare Aleutian migrants physiologically for long-distance migration to winter sites, and in spring to enable emperor geese that migrate different distances to reach comparable levels of condition before nesting.

Alaska↗
USGS2010

Comparing maps of mean monthly surface temperature and precipitation for Alaska and adjacent areas of Canada produced by two different methods

Maps of mean monthly surface temperature and precipitation for Alaska and adjacent areas of Canada, produced by Oregon State University's Spatial Climate Analysis Service (SCAS) and the Alaska Geospatial Data Clearinghouse (AGDC), were analyzed. Because both sets of maps are generally available and in use by the community, there is a need to document differences between the processes and input data sets used by the two groups to produce their respective set of maps and to identify similarities and differences between the two sets of maps and possible reasons for the differences. These differences do not affect the observed large-scale patterns of seasonal and annual variability. Alaska is divided into interior and coastal zones, with consistent but different variability, separated by a transition region. The transition region has high interannual variability but low long-term mean variability. Both data sets support the four major ecosystems and ecosystem transition zone identified in our earlier work. Differences between the two sets of maps do occur, however, on the regional scale; they reflect differences in physiographic domains and in the treatment of these domains by the two groups (AGDC, SCAS). These differences also provide guidance for an improved observational network for Alaska. On the basis of validation with independent in situ data, we conclude that the data set produced by SCAS provides the best spatial coverage of Alaskan long-term mean monthly surface temperature and precipitation currently available.

Alaska, British Columbia, Northwest Territories, Y↗
USGS2010

Movements of walruses radio-tagged in Bristol Bay, Alaska

Satellite radio-location data from 57 adult male Pacific walruses ( Odobenus rosmarus divergens ) were used to estimate haul-out fidelity, broadly describe seasonal foraging distributions, and determine the approximate timing of autumn migration from Bristol Bay, Alaska. Data were collected intermittently during 1987–91 and 1995–2000, primarily during the period from May to October. Transmitter longevity ranged from less than 1 day to 560 days (median 75 d). The four tagging sites were the only haul-outs that were commonly used in the bay from spring through autumn. Mean fidelity, defined as the chance that an animal will return to an area where it previously hauled out, was 0.56 (SE = 0.09). However, small sample sizes precluded comparisons of fidelity among years and among haul-outs by season. No tagged animals migrated out of the bay between spring and early autumn. Combined monthly locations suggest that foraging occurred primarily in the southern and eastern areas of the bay in spring and gradually shifted towards northwestern areas in late autumn and winter. Ninety-eight percent of the in-water locations were in waters under 60 m deep, which account for 76% of the study area. Some animals migrated out of the bay in late autumn and winter; others remained within the bay throughout the year. Those making long-range migrations departed the bay during November and December.

Alaska↗
USGS2012

The utility of harvest recoveries of marked individuals to assess polar bear (Ursus maritimus) survival

Management of polar bear ( Ursus maritimus ) populations requires the periodic assessment of life history metrics such as survival rate. This information is frequently obtained during short-term capture and marking efforts (e.g., over the course of three years) that result in hundreds of marked bears remaining in the population after active marking is finished. Using 10 additional years of harvest recovery subsequent to a period of active marking, we provide updated estimates of annual survival for polar bears in the Baffin Bay population of Greenland and Canada. Our analysis suggests a decline in survival of polar bears since the period of active marking that ended in 1997; some of the decline in survival can likely be attributed to a decline in springtime ice concentration over the continental shelf of Baffin Island. The variance around the survival estimates is comparatively high because of the declining number of marks available; therefore, results must be interpreted with caution. The variance of the estimates of survival increased most substantially in the sixth year post-marking. When survival estimates calculated with recovery-only and recapture-recovery data sets from the period of active marking were compared, survival rates were indistinguishable. However, for the period when fewer marks were available, survival estimates were lower using the recovery-only data set, which indicates that part of the decline we detected for 2003 – 09 may be due to using only harvest recovery data. Nevertheless, the decline in the estimates of survival is consistent with population projections derived from harvest numbers and earlier vital rates, as well as with an observed decline in the extent of sea ice habitat.

Baffin Bay↗
USGS2010

Allocating harvests among polar bear stocks in the Beaufort Sea

Recognition that polar bears are shared by hunters in Canada and Alaska prompted development of the “Polar Bear Management Agreement for the Southern Beaufort Sea.” Under this Agreement, the harvest of polar bears from the southern Beaufort Sea (SBS) is shared between Inupiat hunters of Alaska and Inuvialuit hunters of Canada. Quotas for each jurisdiction are to be reviewed annually in light of the best available scientific information. Ideal implementation of the Agreement has been hampered by the inability to quantify geographic overlap among bears from adjacent populations. We applied new analytical procedures to a more extensive radiotelemetry data set than has previously been available to quantify that overlap and thereby improve the efficacy of the Agreement. We constructed a grid over the eastern Chukchi Sea and Beaufort Sea and used twodimensional kernel smoothing to assign probabilities to the distributions of all instrumented bears. A cluster analysis of radio relocation data identified three relatively discrete groups or “populations” of polar bears: the SBS, Chukchi Sea (CS), and northern Beaufort Sea (NBS) populations. With kernel smoothing, we calculated relative probabilities of occurrence for individual members of each population in each cell of our grid. We estimated the uncertainty in probabilities by bootstrapping. Availability of polar bears from each population varied geographically. Near Barrow, Alaska, 50% of harvested bears are from the CS population and 50% from the SBS population. Nearly 99% of the bears taken by Kaktovik hunters are from the SBS. At Tuktoyaktuk, Northwest Territories, Canada, 50% are from the SBS and 50% from the NBS population. We displayed the occurrence of bears from each population as probabilities for each cell in our grid and as maps with contour lines delineating changes in relative probability. This new analytical approach will greatly improve the accuracy of allocating harvest quotas among hunting communities and jurisdictions while assuring that harvests remain within the bounds of sustainable yield.

Alaska, Northwest Territories, Yukon↗
USGS2013

Coping with the cold: An ecological context for the abundance and distribution of rock sandpipers during winter in upper Cook Inlet, Alaska

Shorebirds are conspicuous and abundant at high northern latitudes during spring and summer, but as seasonal conditions deteriorate, few remain during winter. To the best of our knowledge, Cook Inlet, Alaska (60.6˚ N, 151.6˚ W), is the world’s coldest site that regularly supports wintering populations of shorebirds, and it is also the most northerly nonbreeding location for shorebirds in the Pacific Basin. During the winters of 1997–2012, we conducted aerial surveys of upper Cook Inlet to document the spatial and temporal distribution and number of Rock Sandpipers (Calidris ptilocnemis) using the inlet. The average survey total was 8191 ± 6143 SD birds, and the average of each winter season’s highest single-day count was 13 603 ± 4948 SD birds. We detected only Rock Sandpipers during our surveys, essentially all of which were individuals of the nominate subspecies (C. p. ptilocnemis). Survey totals in some winters closely matched the population estimate for this subspecies, demonstrating the region’s importance as a nonbreeding resource to the subspecies. Birds were most often found at only a handful of sites in upper Cook Inlet, but shifted their distribution to more southerly locations in the inlet during periods of extreme cold. Two environmental factors allow Rock Sandpipers to inhabit Cook Inlet during winter: 1) an abundant bivalve (Macoma balthica) food source and 2) current and tidal dynamics that keep foraging substrates accessible during all but extreme periods of cold and ice accretion. C. p. ptilocnemis is a subspecies of high conservation concern for which annual winter surveys may serve as a relatively inexpensive population-monitoring tool that will also provide insight into adaptations that allow these birds to exploit high-latitude environments in winter.

Alaska↗
USGS2013

Residency times and patterns of movement of postbreeding dunlin on a subarctic staging area in Alaska

Understanding how individuals use key resources is critical for effective conservation of a population. The Yukon-Kuskokwim Delta (YKD) in western Alaska is the most important postbreeding staging area for shorebirds in the subarctic North Pacific, yet little is known about movements of shorebirds there during the postbreeding period. To address this information gap, we studied residency times and patterns of movement of 17 adult and 17 juvenile radio-marked Dunlin (Calidris alpina) on the YKD between early August and early October 2005. Throughout this postbreeding period, during which Dunlin were molting, most birds were relocated within a 130 km radius of their capture site on the YKD, but three birds were relocated more than 600 km to the south at estuaries along the Alaska Peninsula. On average, juvenile Dunlin were relocated farther away from the banding site (median relocation distance = 36.3 km) than adult Dunlin (median relocation distance = 8.8 km). Post-capture, minimum lengths of stay by Dunlin on the YKD were not significantly different between juveniles (median = 19 days) and adults (median = 23 days), with some birds staging for more than 50 days. Body mass at time of capture was the best single variable explaining length of stay on the YKD, with average length of stay decreasing by 2.5 days per additional gram of body mass at time of capture. Conservation efforts for postbreeding shorebirds should consider patterns of resource use that may differ not only by age cohort but also by individual condition.

Alaska↗
USGS2014

Aggression and coexistence in female caribou

Female caribou ( Rangifer tarandus ) are highly gregarious, yet there has been little study of the behavioral mechanisms that foster coexistence. Quantifying patterns of aggression between male and female, particularly in the only cervid taxa where both sexes grow antlers, should provide insight into these mechanisms. We asked if patterns of aggression by male and female caribou followed the pattern typically noted in other polygynous cervids, in which males display higher frequencies and intensity of aggression. From June to August in 2011 and 2012, we measured the frequency and intensity of aggression across a range of group sizes through focal animal sampling of 170 caribou (64 males and 106 females) on Adak Island in the Aleutian Archipelago, Alaska. Males in same-sex and mixed-sex groups and females in mixed-sex groups had higher frequencies of aggression than females in same-sex groups. Group size did not influence frequency of aggression. Males displayed more intense aggression than females. Frequent aggression in mixed-sex groups probably reflects lower tolerance of males for animals in close proximity. Female caribou were less aggressive and more gregarious than males, as in other polygynous cervid species.

Alaska↗
USGS2014

Storm-surge flooding on the Yukon-Kuskokwim Delta, Alaska

Coastal regions of Alaska are regularly affected by intense storms of ocean origin, the frequency and intensity of which are expected to increase as a result of global climate change. The Yukon-Kuskokwim Delta (YKD), situated in western Alaska on the eastern edge of the Bering Sea, is one of the largest deltaic systems in North America. Its low relief makes it especially susceptible to storm-driven flood tides and increases in sea level. Little information exists on the extent of flooding caused by storm surges in western Alaska and its effects on salinization, shoreline erosion, permafrost thaw, vegetation, wildlife, and the subsistence-based economy. In this paper, we summarize storm flooding events in the Bering Sea region of western Alaska during 1913 – 2011 and map both the extent of inland flooding caused by autumn storms on the central YKD, using Radarsat-1 and MODIS satellite imagery, and the drift lines, using high-resolution IKONOS satellite imagery and field surveys. The largest storm surges occurred in autumn and were associated with high tides and strong (> 65 km hr-1) southwest winds. Maximum inland extent of flooding from storm surges was 30.3 km in 2005, 27.4 km in 2006, and 32.3 km in 2011, with total flood area covering 47.1%, 32.5%, and 39.4% of the 6730 km 2 study area, respectively. Peak stages for the 2005 and 2011 storms were 3.1 m and 3.3 m above mean sea level, respectively—almost as high as the 3.5 m amsl elevation estimated for the largest storm observed (in November 1974). Several historically abandoned village sites lie within the area of inundation of the largest flood events. With projected sea level rise, large storms are expected to become more frequent and cover larger areas, with deleterious effects on freshwater ponds, non-saline habitats, permafrost, and landscapes used by nesting birds and local people.

Alaska↗
USGS2016

Habitat use and foraging patterns of molting male Long-tailed Ducks in lagoons of the central Beaufort Sea, Alaska

From mid-July through September, 10 000 to 30 000 Long-tailed Ducks ( Clangula hyemalis ) use the lagoon systems of the central Beaufort Sea for remigial molt. Little is known about their foraging behavior and patterns of habitat use during this flightless period. We used radio transmitters to track male Long-tailed Ducks through the molt period from 2000 to 2002 in three lagoons: one adjacent to industrial oil field development and activity and two in areas without industrial activity. We found that an index to time spent foraging generally increased through the molt period. Foraging, habitat use, and home range size showed similar patterns, but those patterns were highly variable among lagoons and across years. Even with continuous daylight during the study period, birds tended to use offshore areas during the day for feeding and roosted in protected nearshore waters at night. We suspect that variability in behaviors associated with foraging, habitat use, and home range size are likely influenced by availability of invertebrate prey. Proximity to oil field activity did not appear to affect foraging behaviors of molting Long-tailed Ducks.

Beaufort Sea↗
USGS2004

Modeling the effects of human activity on Katmai brown bears (Ursus arctos) through the use of survival analysis

Brown bear-human interactions were observed in 1993, 1995, and 1997 at Kulik River in Katmai National Park and Preserve, Alaska. We analyzed these interactions using survival analysis, creating survival curves for the time that bears remained on the river in the presence, and absence, of human activity. Bear-only survival curves did not vary significantly between years (p = 0.067). Ninety-seven percent of bears left the river within 70 minutes of arrival in all years. Temporal patterns of bear activity were unaffected by the presence of humans as long as the bears did not share river zones with humans (p = 0.062 to p = 0.360). When people and bears did not share river zones, 38.6% (1993), 36.0% (1995), and 37.0% (1997) of bears remained on the river for at least 10 minutes after arrival. In contrast, when people and bears shared river zones, fewer bears remained on the river after the first 10 minutes, with 28.6% (1993), 25.0% (1995), and 32.6% (1997) observed in each year. We conclude that human activity displaced 26.0% (1993), 30.5% (1995), and 12.0% (1997) of the bears using the river, which otherwise would likely have remained longer. Over the three years of study, habituation to human activity may account for observed changes in bears' use of the river.

Alaska↗
USGS2003

Polar bear aerial survey in the eastern Chukchi Sea: A pilot study

Alaska has two polar bear populations: the Southern Beaufort Sea population, shared with Canada, and the Chukchi/Bering Seas population, shared with Russia. Currently a reliable population estimate for the Chukchi/Bering Seas population does not exist. Land-based aerial and mark-recapture population surveys may not be possible in the Chukchi Sea because variable ice conditions, the limited range of helicopters, extremely large polar bear home ranges, and severe weather conditions may limit access to remote areas. Thus line-transect aerial surveys from icebreakers may be the best available tool to monitor this polar bear stock. In August 2000, a line-transect survey was conducted in the eastern Chukchi Sea and western Beaufort Sea from helicopters based on a U.S. Coast Guard icebreaker under the "Ship of Opportunity" program. The objectives of this pilot study were to estimate polar bear density in the eastern Chukchi and western Beaufort Seas and to assess the logistical feasibility of using ship-based aerial surveys to develop polar bear population estimates. Twenty-nine polar bears in 25 groups were sighted on 94 transects (8257 km). The density of bears was estimated as 1 bear per 147 km² (CV = 38%). Additional aerial surveys in late fall, using dedicated icebreakers, would be required to achieve the number of sightings, survey effort, coverage, and precision needed for more effective monitoring of population trends in the Chukchi Sea.

Alaska↗

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