Great White Hunters
Weighing in about twice the size of Siberian tigers, polar bears and their Kodiak cousins are among the world’s biggest land-based predators. But don’t let that fool you – polar bears are just as dependent on water as they are on terra firma.
Polar bears are considered both marine and land mammals because they spend most of their time on the ice and in the ocean. These white giants are expert swimmers and rely on the ocean for their favorite dietary staple of seals. A truly circumpolar Arctic animal, polar bears are tied to the pack ice. They travel from tundra to fast ice and pack ice in search of food like ringed, bearded and sometimes harp seals, as well as an occasional whale calf.
Because their favorite prey – ringed seals – depend on snow and fast ice for their underground birthing lairs and molting territory, polar bears also rely on snow and ice floes for survival.
Polar bears practice unique hunting strategies that work well in their environment. They sit quietly by breathing holes of seals, waiting patiently for one to pop up within reach. Polar bears use their massive paws to deftly sweep the surfacing seal out of the water. Bears also have a keen sense of smell, and they can even detect seal pups buried well under the snow.
When food is plentiful, polar bears eat just the fat and skin and leave the rest of the meal for other Arctic carnivores and scavengers, like the foxes, birds and young bears. What might prompt such an act of generosity? More than just a matter of taste, this might be a water conservation tactic. This lower protein diet, where the bear leaves behind the muscle and organs, results in the bear producing less urea – that means they don’t need to eat as much snow for water in the winter if they eat more blubber and less lean meat.
Though other animals comprise 90% of the polar bear diet, these bears aren’t as picky when food is scarce. In the summer, polar bears spend more time on the tundra because the fast ice isn’t around to provide easy access to seal populations. The bears eat fish, plants, small animals, birds, and sometimes even young walruses, musk ox or reindeer. Polar bears rarely ever tangle with an adult walrus, which can be twice the weight of a bear!
And yes, polar bears have been known to eat humans, though it’s a rare occurrence (rare meaning infrequent, not uncooked). To polar bears, humans are no different than any other potential meal. Of course, this could be considered fair and reciprocal since humans have threatened bear populations by hunting them on a much larger scale.
White Is The New Black
White is great camouflage in the Arctic. Unlike other Arctic mammals, polar bears stay white even in the warm summer months – which means white is “in” all year round. Their fur outer-coat is comprised of long, air-filled guard hairs that are really translucent instead of white. These hairs are very strong, plus they’re waterproof and buoyant in water. After a swim, the bears simply roll in the snow or shake off the water before it freezes. The guard hairs trap heat and protect a soft, fluffy, down-like undercoat that insulates the bears in Arctic temperatures. The polar bear’s long legs are covered with dense fur, and even their feet and soles are hairy. The soles of their feet also feature small bumps that keep them from slipping on ice.
Like other polar animals, polar bears also rely on a thick layer of blubber to keep them warm. They have other adaptive features, like tiny eyes and short, round, furry ears. Their small heads and dignified Roman noses work well for swimming, which the bears keep above water while practicing the breast stroke from ice floe to ice floe.
These animals wrote the book on “layering for cold” and dressing for winter survival.
Though you can’t tell by looking, their skin (base layer) is even black to retain the maximum amount of heat. The problem? Polar bears can overheat quickly when they run, even in cold temperatures. That gives caribou and musk oxen an advantage if a chase ensues! (Typically, the bear is chasing the caribou, and not the other way around.)
Polar bears are also known for their immense size – they’re huge! The males are sometimes two to three times bigger than the females. They’re 1.6 meters (5 feet) tall at the shoulder, 410 to 770 kgs (900 – 1700 lbs) in weight, and 2 to 3 meters (6’ 6” – 9’ 9”) long. They tower over us humans when they stand up and rear on their hind feet.
The Lonely Planet travel books could have been named for the polar bear. They’re not very social animals. The males spend most of their time swimming solo, following the ice and its hunting opportunities. Female polar bears at least have the company of their two cubs before they kick them out of the den and propagate another set of babies.
Hunting and breeding seem to provide the best (and maybe only) social settings. Polar bears do their courting in the spring, from March to May. Females become sexually mature at ages four to six, and the males are ready to breed a little younger. It’s a brief relationship, since the males take off soon after the deed is done, and the females go into a feeding frenzy that prepares them for maternity leave. The implantation of the egg is delayed until Fall (September through October), when the female digs a snow cave that she’ll call home for the winter.
Polar bears don’t go into a true hibernation. With true hibernators, the animal’s heart rate slows remarkably and the body temperature drops to nearly 0 degrees C (32 degrees F).
Only female polar bears (not males) enter the den for the winter fast, and they go into a walking hibernation – or dormancy – that isn’t as deep as true hibernation.
In early winter, the female polar bear usually gives birth to two tiny and helpless cubs that are about 30-35 cm (12-14 inches) long and weigh 500-700 grams (1 to 1-1/2 pounds).
Like other bear cubs, these newborns are blind, nearly naked, and completely dependent on their mother while in the den. With the help of super-rich, high-fat (31%) milk, they gain about 10kg (20 plus pounds) by the time they emerge from the den in March or April.
They’re virtual prodigies in that they walk at 1-1/2 months old and start eating solid food at four or five months.
Most cubs stay with their mother for 2-1/2 years to learning hunting and survival techniques before going their separate ways. At that time, the female is ready to start the maternal cycle all over again. With a lifespan of 15 to 18 years in the wild (with some living into their 30’s), a female might have up to five litters of cubs over her lifespan!
Protecting This Predator
Official bear counters estimate that 20,000 to 27,000 polar bears populate the Arctic region, and the numbers are decreasing. They travel as far north as the open sea, and reach 80 degrees in the summer, and they go as far south as James Bay in Canada. Polar bear sub-populations range from Labrador to Alaska’s Yukon to Spitsbergen, Norway.
In 1972, the United States covered polar bears under its Marine Mammal Protection Act (MMPA), and in 1975 the polar bear was identified as a “threatened” species.
In 1973, five polar bear nations – Canada, Greenland, Norway, the United States, and the former Soviet Union – signed an agreement to protect polar bear habitat such as den areas, feeding areas, and migratory routes. This International Agreement on Conservation of Polar Bears and Their Habitat also banned hunting the bears from the air and from motorized boats, and it set some guidelines regarding the management of polar bears.
Now there is a huge push to get the polar bear placed on the endangered species list, due to its declining habitat and numbers. The biggest threat to today’s polar bear population seems to be melting ice in the Arctic.
[TRIP TRIVIA: Svalbard on Spitsbergen is known for its polar bear watching. And if you’re watching them, they’re watching you – so watch out! Your group is required to carry a weapon when wandering in polar bear territory, but the bears are also protected by law. That means confrontations are troublesome in more ways than the obvious one! Make it easy on the bears and yourselves by giving them plenty of room to roam.]