when were polar bears first discovered?
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The mystery has been solved thanks to a very lucky find. In 2004, Icelandic geologist Ólafur Ingólfsson of the University of Iceland was working on Svalbard. While studying sediment layers in the island’s coastal cliffs, he accidentally discovered a lower jawbone belonging to a large predator. Ingólfsson gave the bone to researchers at the University of Oslo’s Natural History Museum, who, along with colleagues, have studied it for several years.
Based on its shape and chemistry, the researchers have determined that the jaw belonged to a bear that ate marine organisms. And its location in the sediment places its age at somewhere between 110,000 and 130,000 years old, which would make about twice as old as the oldest polar bear remains ever found.
“It’s a truly ancient polar bear,” says lead author and geneticist Charlotte Lindqvist of the University at Buffalo in New York state. It must have lived close to the time when the species had split off from the so-called ABC brown bears, which inhabit three islands—Admiralty, Baranof, and Chichagof—in southeastern Alaska. Those bears are more closely related to polar bears than they are to other brown bears, she says.
Polar bear
Polar bears are the largest carnivorous land mammals on Earth. They are about seven to eight feet long, measured from the nose to the tip of their very short tail.
Male polar bears are much larger than the females. A large male can weigh more than 1,700 pounds, while a large female is about half that size (up to 1,000 pounds). Bears can weigh about 50 percent more after a successful hunting season than they do at the start of the next; most of this additional weight is accumulated fat. A newborn polar bear weighs only about 1.5 pounds.
Many of the polar bear’s physical adaptations help it maintain body heat and deal with its icy habitat. The bear’s outer layer of fur is hollow and reflects light, giving the fur a white color that helps the bear remain camouflaged. The skin under the polar bear’s fur is actually black; this black is evident only on the nose.
Polar bears also have a thick layer of fat below the surface of the skin, which acts as insulation on the body to trap heat. This is especially important while swimming and during the frigid Arctic winter. The bear’s large size reduces the amount of surface area that’s exposed to the cold per unit of body mass (pounds of flesh), which generates heat.
RANGE
Most polar bears occur north of the Arctic Circle to the North Pole. There are some populations south of the Arctic Circle in the Hudson Bay of Manitoba, Canada. Polar bears live in Alaska, Canada, Russia, Greenland, and some northern islands owned by Norway, such as Svalbard.
Polar bears depend on the sea ice, which forms above the open waters where their seal prey lives. They will spend time on land when sea ice is not available (and most pregnant polar bear females make their dens on shore near the coast). Polar bears are excellent swimmers, and they travel long distances between shore and the sea ice if necessary.
However, if a storm kicks up during these increasingly long swims (caused by the warming ocean), they can drown. These long swims and storms are also often difficult for cubs. During periods of ice breakup, polar bears frequently swim between floating ice islands.
DIET
Unlike other bear species, polar bears are almost exclusively meat eaters (carnivorous). They mainly eat ringed seals, but may also eat bearded seals. Polar bears hunt seals by waiting for them to come to the surface of sea ice to breathe. When the seal nears the surface, the polar bear will bite or grab the seal and pull it onto land to feed. They also eat walruses and whale carcasses. Polar bears will search out bird eggs and other food sources, but none of these are abundant enough to sustain the large body mass and dense populations of polar bears.
Another vitally important food source in most areas are seal pups that are born and live in dens in the Arctic ice. The polar bear identifies these dens by smell and other markers and pounces though the roof of the den to capture the young seals. In Hudson Bay, the availability of seal pups in the spring is increasingly limited by earlier melting of ice. In the Arctic, polar bears are at the top of the food chain; they eat everything and nothing (except native hunters) eats them.
BEHAVIOR
Polar bears tend to live solitary lives except when mating, when a female raising her cubs forms a family group, or when many bears are attracted to a food source like a beached whale.
Young polar bears spending the summer ashore on the Hudson Bay coast will frequently play with each other, most commonly with their siblings.
Polar bears near Churchill on the coast of Hudson Bay are even known to play with chained sled dogs without killing them, which they could easily do.
LIFE HISTORY
When the cubs are born, they are completely dependent on their mother. They stay in the den nursing on her rich milk until spring, when they emerge and start exploring the world as their mother heads out to the ice to catch the seals she needs to replenish the weight she’s lost during her period of fasting.
Over the next two years, the cubs will learn from their mother how to catch seals themselves and to develop the other skills needed to survive and grow to adult size. Typically cubs will stay with their mother until they are two-and-a-half years old, but in some cases they will stay for a year more or a year less. If the mother is able to replenish her fat reserves sufficiently, she can produce a litter of cubs that survive until weaning every three years.
When food declines in abundance, there is a longer period between successive successful litters, and litter sizes are smaller. Polar bears in the wild can live to be 30 years of age, but this is rare. Most adults die before they reach 25 years.
The conditions developing in Hudson Bay are such that females will no longer be able to birth and successfully raise a little of cubs. When this happens, the adult bears will survive until they die of old age and the population will be doomed.
Scientists are fearful that this pattern is also starting to happen in the more northern polar bear populations as the amount of Arctic ice continues to shrink.
CONSERVATION
Polar bears are in serious danger of going extinct due to climate change. In 2008, the polar bear became the first vertebrate species to be listed under the U.S. Endangered Species Act as threatened due to predicted climate change. The Secretary of Interior listed the polar bear as threatened but restricted the Endangered Species Act’s protections, and thus the polar bear’s future is still very much in jeopardy.
The chief threat to the polar bear is the loss of its sea ice habitat due to climate change. As suggested by its specific scientific name (Ursus maritimus), the polar bear is actually a marine mammal that spends far more time at sea than it does on land.
It’s on the Arctic ice that the polar bear makes its living, which is why climate change is such a serious threat to its well-being. Polar bears are being impacted by climate change in several ways.
Population sizes are decreasing:
In southern portions of their range around Hudson Bay, Canada, there is no sea ice during the summer, and the polar bears must live on land until the bay freezes in the fall, when they can again hunt on the ice. While on land during the summer, these bears eat little or nothing. In just 20 years, the ice-free period in Hudson Bay has increased by an average of 20 days, cutting short polar bears’ seal hunting season by nearly three weeks.
The ice is freezing later in the fall, but it is the earlier spring ice melt that is especially difficult for the bears. They have a narrower time frame in which to hunt during the critical season when seal pups are born, and average bear weight has dropped by 15 percent. The bears have fewer cubs, and of the cubs they do have, the frequency of survival to adulthood is decreasing. In addition, the interval between successful litters is growing. As a result, the Hudson Bay population is down more than 20 percent. The patterns seen in Hudson Bay are beginning to occur now in more northern populations and is especially well documented on the north coast of Alaska, but appears to be the case worldwide.
Sea ice platforms are moving farther apart:
The retreat of ice has implications beyond the obvious habitat loss. Remaining ice is farther from shore, making it less accessible. After each summer, the trend seen in the Arctic is for sea ice to be farther from shore, making it necessary for polar bears to swim increasingly long distances from shore to reach the ice. Worse, the last remaining sea ice is over deep and unproductive waters that yield less prey.
The larger gap of open water between the ice and land also contributes to rougher wave conditions, making the bears’ swim from shore to sea ice more hazardous. In 2004, biologists discovered four drowned polar bears in the Beaufort Sea. Never before observed, biologists attributed the drowning to a combination of retreating ice and rougher seas.
As a result of rapid ice melt in 2011, a female polar bear reportedly swam for nine days nonstop across the Beaufort Sea before reaching an ice floe, costing her 22 percent of her weight and her cub. As climate change melts sea ice, the U.S. Geological Survey projects that two thirds of polar bears will disappear by 2050.
Food scarcity is increasing:
As sea ice disappears for longer and longer periods during the late summer, polar bears are left with insufficient time to hunt. Polar bears can only survive in areas where the oceans freeze, allowing them to hunt seals living under, on, or in the frozen polar ice cap. Exacerbating the problems of the loss of hunting areas, it is expected that the shrinking polar ice cap will also cause a decline in polar bears’ favorite prey—seals.
The reduction in ice platforms near productive areas for the fish eaten by seals is affecting the seals’ nutritional status and reproduction rates.
Polar bears are going hungry for longer periods of time, resulting in cannibalistic behavior. Although it has long been known polar bears will kill for dominance or kill cubs so they can breed with the female, outright predation for food was previously unobserved by biologists.
Additionally, development is increasing in ocean floor exploration and offshore oil extraction in the open waters that were previously sealed by frozen ice.
This brings people, disturbance, and potentially ruinous oil spills to the previously pristine Arctic polar bear habitat. Polar bears need our help and protection to ensure a long, healthy future for the species.
The best way for people to help polar bears is by reducing carbon emissions and working with the National Wildlife Federation to campaign for reductions in climate change pollutants.
