Ringed seals ( Phoca hispida Schreber, 1775 = Pusa hispida (Schreber, 1775)) and bearded seals ( Erignathus barbatus (Erxleben, 1777)) represent the majority of the polar bear ( Ursus maritimus Phipps, 1774) annual diet. However, remains of lower trophic level bowhead whales ( Balaena mysticetus L., 1758) are available in the southern Beaufort Sea and their dietary contribution to polar bears has been unknown. We used stable isotope (13C/12C, δ13C, 15N/14N, and δ15N) analysis to determine the diet composition of polar bears sampled along Alaska’s Beaufort Sea coast in March and April 2003 and 2004. The mean δ15N values of polar bear blood cells were 19.5‰ (SD = 0.7‰) in 2003 and 19.9‰ (SD = 0.7‰) in 2004. Mixing models indicated bowhead whales composed 11%–26% (95% CI) of the diets of sampled polar bears in 2003, and 0%–14% (95% CI) in 2004. This suggests significant variability in the proportion of lower trophic level prey in polar bear diets among individuals and between years. Polar bears depend on sea ice for hunting seals, and the temporal and spatial availabilities of sea ice are projected to decline. Consumption of low trophic level foods documented here suggests bears may increasingly scavenge such foods in the future.

Polar bears (Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004)(2005)(2006)(2007)(2008)(2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.Résumé : L'ours blanc (Ursus maritimus Phipps, 1774) dépend de la banquise pour chasser les mammifères marins dont il se nourrit. Les diminutions récentes de la banquise ont été corrélées au déclin de l'état corporel, du taux de survie et de la taille de la population de cet animal. S'il est postulé que la réduction du nombre de possibilités d'alimentation constitue la principale cause du déclin de l'ours blanc associé à l'état de la banquise, les coûts de déplacements dans un contexte de banquise détériorée pourraient également être un facteur explicatif. Nous avons utilisé des données sur les déplacements de 52 ourses blanches adultes portant des colliers à système de localisation GPS, dont certaines accompagnées de jeunes dépendants, pour documenter leurs déplacements à la nage sur de longues distances (>50 km) dans la partie méridionale des mers de Beaufort et de Tchoukotka. En six ans (2004)(2005)(2006)(2007)(2008)(2009), nous avons recensé 50 déplacements à la nage de longue distance par 20 ourses. La durée et la distance de ces déplacements allaient de 0,7 à 9,7 jours (moyenne de 3,4 jours) et de 53,7 à 687,1 km (moyenne de 154,2 km), respectivement. La fréquence des déplacements à la nage a semblé augmenter au cours de l'étude. Nous démontrons que les ourses blanches adultes et leurs oursons sont capables de parcourir de longues distances à la nage en périodes caractérisées par la présence de vastes étendues d'eaux libres. À ces déplacements de longue distance à la nage semble toutefois être associée une plus forte demande énergétique que pour les déplacements sur la banquise. Nos observations suggèrent que les déplacements de longue distance à la nage constituent un changement de comportement en réponse au déclin de l'état de la ban...

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Anthropogenic global warming is occurring more rapidly in the Arctic than elsewhere, and has already caused significant negative effects on sea icedependent species such as polar bears. Although observed effects have thus far been gradual, the large amount of annual variation in the climate system may cause habitat changes in individual years that exceed the long-term trend. Such years may be below critical thresholds necessary for feeding and result in unprecedented reductions in survival, reproduction, and abundance in some populations. Here, in anticipation of sudden negative population-level effects, we provide an overview of proactive conservation and management options. Preplanning, consultation, and coordination of management responses will be necessary to reduce the risks to human safety and other effects of catastrophic declines in habitat. Advance consideration of the costs, legality, logistical difficulties, likelihood of success, and invasiveness of potential responses will be critical to minimizing short-term negative effects while laying the groundwork for longer-term conservation objectives.