A growing and vital field of polar bear studies is research into energetics: the study of how animals take in and expend calories.
Like all animals, polar bears need to take in energy through feeding, and they use those calories to move, grow, produce offspring, and keep cells and tissues healthy.
Why This Research Matters
As large, predatory mammals, polar bears require vast amounts of energy — but their ability to hunt is being compromised by declines in the sea ice habitat where they catch seals. Less hunting habitat means fewer seals and fewer calories coming in, leaving polar bears with less energy available for reproduction and basic health functions, like repairing tissues and fighting off infections.
The specific prey is also important: polar bear physiology is uniquely well-adapted for digesting and storing fat, limiting their ability to replace blubber with other types of food, including most land-based foods.
To understand these pressures, researchers use predictive models that analyze how sea ice availability influences the bears’ energy budget — the balance of calories consumed versus calories spent — and their body fat storage.
Because all animals need to take in and expend energy, this approach can also help us understand how populations in less well studied regions might respond to changes in sea ice. This research is key to gaining a detailed understanding of how climate change will affect polar bears into the future and how responses may unfold across the Arctic.
What We’re Learning
-
Energy models can forecast outcomes like starvation, reduced lactation, or cub survival, and they have proven accurate in reconstructing and explaining recent population changes in Western Hudson Bay via changes in the energy balance of individual polar bears. They are now being used to estimate how polar bears will respond to future scenarios and timelines of warming, which can inform conservation planning and policy.
-
Polar bears forage on land, but lose weight: A study using video-collar cameras worn by polar bears found that although they foraged on various foods on land, including berries, birds and small mammals, on average, all bears lost similar body weight during the study. The absence of high-fat foods on land like seal blubber means that polar bears deplete their body fat reserves as they spend longer periods off the sea ice, eventually impairing reproduction and risking their survival.
-
Energy intake is vital to polar bears on the sea ice as well: bears can gain large amounts of body fat over short intervals feeding on seals, but can also lose weight quickly between meals due to their large size and high energy demands.
-
Changes to hunting success or prey availability on the ice can further impact polar bears’ ability to accumulate the large amounts of body fat they need to sustain themselves across the year. Alternative prey like belugas don’t replace the energy polar bears gain from seals.
-
Short-term climate impacts can be dependent on local conditions: Though polar bears ultimately need sufficient sea ice habitat to support their high-fat diet and high energy demands, local variation in food availability may partially buffer polar bears in some regions in the short term.
What’s Next
Upcoming research is looking at how energy intake and expenditure varies in different populations, and how behaviour and food availability can affect this. This research will give us better insight into when and how different populations may respond to changing sea ice conditions to inform monitoring and management efforts.