Polar bears on Norwegian islands fatter and healthier despite ice loss, scientists say | BBC News

Key Concepts

• Polar Bear Adaptation: The ability of polar bears to adjust their diet and hunting strategies in response to declining sea ice.
• Sea Ice Decline: The reduction in the extent and thickness of Arctic sea ice due to climate change.
• Alternative Prey: Land-based food sources utilized by polar bears, including reindeer, bird eggs, and walruses.
• Subpopulations: Distinct groups of polar bears geographically isolated and adapted to specific environments.
• Body Condition: A measure of an animal’s fat reserves, used as an indicator of health and survival prospects.

Increased Body Fat in Svalbard Polar Bears Despite Sea Ice Loss

A 30-year study focusing on polar bears in the Norwegian archipelago of Svalbard has revealed a surprising trend: an increase in the average body fat reserves of the bears, despite a significant decline in sea ice. Researchers analyzed the body condition of 770 polar bears, finding that they are “significantly fatter” now compared to the early 1990s. This increase coincides with a rise in temperatures resulting in 100 more ice-free days annually than when the study commenced.

Dietary Shifts and Prey Availability

The observed weight gain is attributed to a shift in the bears’ diet, necessitated by the reduced availability of their primary prey – seals – due to diminishing sea ice. Polar bears in Svalbard are increasingly relying on land-based food sources. Specifically, the study indicates increased consumption of reindeer, bird eggs, and walruses. The resurgence of the walrus population in Svalbard is a key factor; walruses were previously hunted “almost to extinction” but have recovered following protection measures, leading to a greater abundance of this alternative prey source.

Regional Variation in Polar Bear Response to Climate Change

The report highlights that the Svalbard polar bear population’s adaptation is not representative of the entire Arctic region. The Arctic is comprised of 20 different subpopulations of polar bears, each uniquely adapted to its local environment. In Churchill, Canada, researchers observed a contrasting scenario: a decline in the polar bear population due to the loss of sea ice without readily available alternative prey sources. This demonstrates that the success of adaptation is heavily dependent on the availability of suitable land-based food options.

Temporary Adaptation and Future Concerns

Scientists emphasize that the positive trend observed in Svalbard is likely “temporary.” As sea ice continues to recede, polar bears may be forced to travel greater distances between hunting grounds, expending crucial energy reserves. This increased energy expenditure could negate the benefits of the altered diet. The long-term viability of this adaptation strategy remains uncertain.

Expert Commentary

Victoria Gil, BBC News science correspondent, reported on the findings, framing the situation as an “Arctic mystery” regarding the bears’ dietary changes. The study underscores the complex and varied impacts of climate change on Arctic wildlife.

Technical Terms

• Archipelago: A group of islands closely scattered in a body of water. (Svalbard is an archipelago)
• Subpopulation: A geographically distinct group within a larger population, exhibiting unique characteristics.
• Body Condition: A measure of an animal’s nutritional status, often assessed through visual observation or measurements of fat reserves.

Conclusion

The study in Svalbard provides a nuanced perspective on the impact of climate change on polar bears. While some populations demonstrate a capacity for adaptation through dietary shifts, this adaptation is contingent on the availability of alternative prey and is unlikely to be a sustainable solution in all regions of the Arctic. The contrasting situation in Churchill, Canada, underscores the vulnerability of polar bear populations lacking access to sufficient land-based food sources. The findings emphasize the urgent need for continued monitoring and conservation efforts to mitigate the long-term effects of sea ice loss on these iconic predators.