Polar bear survival is intrinsically linked to the presence of sea ice, which is the foundation of its hunting strategy and caloric intake. The loss of Arctic sea ice due to climate change is fundamentally altering the behavior of these animals, forcing them to adapt or face severe consequences. As the ice melts earlier and forms later, the polar bear’s ability to secure the high-fat diet it needs is compromised, directly threatening its long-term survival.
Traditional Polar Bear Hunting Practices
Polar bears primarily hunt ringed and bearded seals, which provide the blubber necessary to sustain their massive bodies. They employ two specialized methods that depend entirely on a stable ice surface. The most common technique is still-hunting, where a bear uses its exceptional sense of smell to locate a seal’s breathing hole, or aglu, in the ice. The bear waits motionless until a seal surfaces for air, then strikes with a powerful pounce to secure its prey.
The second method is stalking, used to hunt seals resting on the ice surface near floes or leads. The bear uses its white camouflage to slowly approach the seal, minimizing vibrations. Once within close range, typically around 12 meters, the bear initiates a sudden, high-speed charge to capture the seal before it escapes into the water. These techniques are highly effective and allow the bear to consume high-calorie prey that provides weeks of energy from a single meal.
The Essential Role of Sea Ice in Hunting Success
Sea ice is the platform that allows the polar bear to access its primary prey. This solid surface serves as both a mobile base and a transport corridor, making the bear an ice-dependent predator. The ice brings the bear into proximity with seal populations, which spend most of their lives in the water beneath the ice.
The ice environment also manages the bear’s energy budget, as moving on a solid surface is significantly more efficient than swimming. Minimizing energy expenditure while hunting is required for the bear to build significant fat reserves. The expansive, flat surface of the ice allows the bear to utilize its acute sense of smell, detecting a seal’s breathing hole from up to one kilometer away. This sensory advantage is largely lost when the bear is forced to hunt from the water.
Direct Impacts of Ice Loss on Traditional Methods
The decline of sea ice directly undermines the established hunting practices polar bears rely upon. The most immediate impact is a shorter hunting season, as the ice is melting earlier and forming later in regions like Hudson Bay. This forces bears to spend longer periods fasting on land, depleting the fat reserves needed to survive and reproduce.
The retreat of the ice edge over deeper waters reduces access to preferred foraging areas, as productive seal habitats are often located over continental shelves. Fragmented and unstable ice makes still-hunting and stalking difficult, since bears cannot hold a patient position at an aglu or approach a resting seal without the ice shifting. These conditions force bears to travel longer distances, increasing energy expenditure while food intake declines. Scientists have correlated these pressures with an approximately 50% population decline in the Western Hudson Bay subpopulation between 1979 and 2021.
Forced Shifts to Alternative Hunting Strategies
When traditional ice-based hunting methods fail, polar bears are increasingly forced to adopt alternative strategies, often involving terrestrial foraging. As they spend longer periods on shore, bears scavenge for bird eggs, nestlings, and marine mammal carcasses, or prey on land animals like caribou and muskox. Some bears also raid human garbage dumps near northern communities, which increases human-wildlife conflict.
These alternative food sources are insufficient to meet the polar bear’s high energy demands. Seals provide a high-fat, calorie-dense meal that terrestrial prey cannot match, as the polar bear’s physiology is specialized for a blubber diet. In the water, bears may attempt riskier aquatic hunts, such as long-distance swims to catch beluga whales or target slower-moving walrus calves. These shifts are energy-intensive, yield less nutritional value, and ultimately result in a decline in the bears’ body condition and reproductive success.