Icon of the Arctic
Standing up to 12 feet tall and weighing up to 1,600 pounds, polar bears have no natural predators. Intelligent, patient, and strong, they are at the top of the Arctic food chain.
Although they are the largest land carnivore on Earth, polar bears are excellent swimmers and spend most of their lives traversing and swimming between sea ice floes. In fact, their scientific name, Ursus maritimus, means sea bear. Because they’re so comfortable in and around water, they’re considered marine mammals, making them unique among bear species.
These big bears of the North are perfectly adapted to the most remote areas and extreme environments of the planet. Along with other unique characteristics, they have water-repellent fur and a thick layer of fat under their skin, attributes which keep them warm in subzero temperatures.
Polar bears are almost exclusively carnivorous and spend more than half their time hunting. They feed primarily on ringed seals and bearded seals, the only animals that provide them with enough fat to fuel their large bodies. An adult seal can supply a bear with enough calories for 11 days!
Why Polar Bears Need Sea Ice
Polar bears spend the winter months at sea, out on the ice, where they hunt seals. The bears wait motionless on the ice, sometimes for hours, above a seal’s breathing hole, then ambush the seal when it comes up for air. This method of hunting relies entirely on the availability of ice on the surface of the ocean that can support a polar bear’s weight.
Being as large as they are, polar bears have enormous appetites. When they feed, they need to eat enough to survive until the next meal, usually four or five days, and still have energy to hunt on days they don’t catch prey. Unlike other bear species, polar bears don’t hibernate. Instead, they spend the winter months hunting seals. When the sea ice melts in summer, the bears are forced ashore, where they endure a low-energy fasting period and lose more than two pounds per day. During the warm season, a polar bear can lose up to 30% of its total body mass—that’s up to 480 pounds!
Pregnant polar bears have even greater, more urgent meal requirements. After an expectant mother bear digs a den in the winter snow, she won’t leave again until spring, when her cubs are big enough to go with her. Changes in her metabolism allow her to go without food and water for as long as eight months. To survive this, she has to store an enormous amount of fat before she dens—reserves that will provide all the nutrition she needs for herself and her nursing cubs until they emerge from the den.
How Climate Change Affects Polar Bears
In recent decades the Arctic has warmed twice as quickly as the rest of the planet, which has melted the sea ice that polar bears require for survival. The bears are working harder to find food, walking and swimming longer distances without regular meals. This depletes their fat reserves, which they can’t replenish quickly enough, causing starvation.
Globally, the greatest cause of warming temperatures is carbon emissions, which are created by burning fossil fuels like coal and oil. Burning coal and oil releases carbon dioxide and other carbon compounds into the atmosphere. These compounds, sometimes called greenhouse gas (GHG) emissions, trap solar energy in the atmosphere, which raises temperatures around the world.
Steadily warming temperatures have melted vast quantities of sea ice and changed its freezing patterns. Every year, the ice freezes later in the fall and melts earlier in the spring. This shortens the polar bears’ hunting season, sometimes by several weeks. Bears don’t have enough time on the ice to catch enough seals to survive the summer fast. And when hungry bears are land-bound for long stretches of time, they wander into towns and villages, where they forage in trash cans and garbage dumps. Practically fearless, polar bears are not easily chased away. When humans and polar bears collide, the encounter is often fatal for both species.
New Threats for Polar Bears
Recent research shows that female bears are having fewer litters of cubs, with fewer cubs per litter, and that more and more cubs are not surviving to adulthood. When polar bear mothers and their cubs emerge from dens in the spring, much of the ice has already disappeared, forcing emaciated mother bears to swim greater distances between ice floes in rough ocean conditions. While starving mother bears hunt for seals among the remaining ice, trying to restore their body mass, their cubs lack the strength, size, and endurance to swim and trek such great distances. But adult bears are succumbing, too. For the first time in recorded history, adult polar bears—sea bears—are being found dead from drowning.
With their fragile habitat melting out from under them, polar bears also face other challenges. Now that some parts of the Arctic are no longer covered by a permanent layer of ice, they have been opened up for oil and natural gas drilling. Testing for these underground resources requires the use of heavy trucks and equipment, which may frighten mother bears into prematurely leaving their dens. The separation of mothers from cubs could have disastrous consequences.
Solutions for Sea Bears
San Diego Zoo Global collaborates extensively with other conservation organizations, government agencies, and research institutions, including Polar Bears International and the U.S. Geological Survey. Together, we’re improving our understanding of polar bears’ ability to adapt to warming temperatures, including how a changing environment affects their abilities to find mates, raise cubs, and survive disease. We’re finding ways to protect polar bears and their habitat from warming temperatures, as well as the problems that follow.
You can help polar bears by reducing your carbon footprint wherever you can:
- Switch to renewable energy sources, like solar or wind power, if you can.
- Consider carpooling or bicycling to work. Or maybe an electric vehicle is right for you.
- Plant a garden and grow some of your own food. Or shop for locally grown produce, which is gentler on the climate because it doesn’t travel as far as commercial products shipped in gas-powered vehicles.
- Tell your elected officials that protecting wildlife and the environment matters to you.
- Reduce, reuse, and recycle as much as possible.
If we can reduce carbon emissions and stabilize global temperatures, sea ice will stop melting and may even come back. It’s not too late to turn things around for polar bears. If we act now, and act together, we can ensure that these magnificent bears survive for generations to come.