Are polar bears endangered? What threats do they face?
Melting sea ice is one of the most pressing threats to polar bears’ survival. Declining ice habitat is already hurting polar bears, but scientists predict even more dramatic reductions in sea ice coverage during the next 50 to100 years. As a result, the polar bear was listed as a threatened species in the United States under the Endangered Species Act in May 2008. The International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species currently classifies the polar bear as ‘vulnerable.’
With receding ice, polar bears have a hard time maintaining their food supply – ringed and bearded seals, which also rely on sea ice. Mother bears cannot pack on enough body weight to nurse their cubs and many bears are left starving. Some bears are even drowning as they swim further and further distances out to sea to find food. Cubs of mother bears who swim too far to find food often perish.
Additional threats to polar bears include:
- Pollution – Many toxins build up in animal fat, and a healthy polar bear diet requires large quantities of fat.
- Industrial development – Industrial development can threaten polar bears by increasing human-bear interactions. It can also affect mother polar bears when they select their dens, or cause them to abandon a den – and their cubs. And the IUCN states that an industrial oil spill in sea ice habitat would probably “result in oil being concentrated in leads and between ice floes resulting in both polar bears and their main prey (ringed and bearded seals) being directly exposed to oil.”
How many polar bears are there?
The IUCN states that 20-25,000 polar bears remain in the wild worldwide. In 2014, a study published in Ecological Applications on polar bears in northeast Alaska (the southern Beaufort Sea) and the Northwest Territories documented a 40 percent polar bear population loss between 2001-2010, dropping from 1,500 to 900 bears.
Polar bears in Alaska rely on “divergent ice” – ice that shrinks further and further from shore, making polar bears swim further and further out to sea in an attempt to reach prey. About 8,000 bears from Canada to Alaska to Russia share this divergent ice.
Polar Bear Diet
Polar bears eat mainly ringed and bearded seals that live in the Pacific Ocean’s Bering Sea, as well as the Beaufort and Chukchi Seas of the Arctic Ocean. They will wait for ringed seals to surface in their breathing holes or stalk them on ice floes. To catch hauled-out seals, they will pounce from as much as 20 feet away.
Polar bears follow ice floes to maintain their food supply, and as sea ice melts and recedes further from shore in the summer, bears must decide either to fast until the ice returns in winter or swim further and further out to sea for the chance to find food.
Polar bears will also eat the occasional small mammal, the remains of other animals like whales, or scavenge eggs from on-shore bird nests. However, consuming seal blubber is critical to allowing them to maintain their needed body weight.
Side note: polar bears will share food if another bear “begs” politely. This involves submissive behavior, circling, and nose bumping.
After eating as much as possible in the summer, pregnant females will make a small snow cave in the fall. Mothers wait for the snow to close the tunnel entrance, and then within their cozy den will give birth to one, two or three tiny cubs during the winter months. Polar bear families generally emerge from their den in March or April when the cubs are strong enough to survive outside and ready to make the trek to the sea ice. Scientists, however, believe disturbances caused by development activities can cause mothers to abandon their dens early, thereby endangering the lives of their newborn cubs.