Primary Diet and Caloric Needs
Polar bears rely almost exclusively on ringed seals and bearded seals for their daily energy. A single adult bear needs roughly 43,000 calories per day, which is equivalent to about 1.5 adult ringed seals every 10 days, according to data from the National Park Service. Their metabolism is so efficient that they can store up to 150 pounds of fat, which sustains them during the ice-free summer fasting period when they cannot hunt.
When seals are scarce, polar bears will scavenge whale carcasses, eat bird eggs, and occasionally hunt small mammals or caribou. These alternative food sources provide only a fraction of the required calories, and a bear cannot survive on them long-term. The global polar bear population is estimated at 22,000 to 31,000 individuals, with the Southern Hudson Bay subpopulation showing measurable declines linked to reduced seal hunting success, as reported by the IUCN Polar Bear Specialist Group.
Hunting Techniques and Ice Dependency
Still-Hunting and Stalking Methods
Polar bears hunt seals primarily by waiting motionless at breathing holes in the sea ice for hours, a technique called still-hunting. They also stalk seals resting on ice floes, using their white fur as camouflage and closing the distance to within 30 feet before a burst of speed. A successful kill provides a bear with roughly 8 days of energy, but success rates have dropped as seasonal ice becomes thinner and less predictable.
Arctic sea ice extent has been declining by approximately 13 percent per decade since satellite records began in 1979, according to the National Snow and Ice Data Center. This loss forces bears to swim longer distances between ice platforms, burning calories they cannot replace. In some regions, such as the western Hudson Bay, the ice-free season has lengthened by about three weeks since the 1980s, directly reducing the window available for seal hunting.
Impact of Climate Change on Food Access
Subpopulation Health and Body Condition
Studies of the Southern Beaufort Sea subpopulation show that average adult body condition has declined measurably since the early 2000s, with fewer cubs surviving to adulthood. The U.S. Geological Survey tracks these trends using capture-and-release data, finding that bears in areas with earlier ice breakup weigh less and have lower reproductive rates. This pattern is consistent across multiple subpopulations in the southern range of the species.
As sea ice diminishes, polar bears increasingly come into contact with human settlements, scavenging garbage and bird eggs to supplement their diet. While this behavior is documented in places like Churchill, Canada, and Svalbard, Norway, it does not provide sufficient nutrition to offset the loss of seal-based calories. The Polar Bear International notes that without significant reductions in greenhouse gas emissions, two-thirds of the world's polar bears could be lost by mid-century due to habitat and food loss.
Energy Deficit and Fasting Periods
Research published in Science indicates that polar bears now face longer fasting periods than their physiology can sustain in many regions. The threshold for survival is roughly 180 days without food, but some subpopulations are already approaching or exceeding this limit during extended ice-free seasons. This energy deficit leads to reduced cub production, lower survival rates, and increased starvation events observed by