Which Animals Never Get Their Sea Legs Planet Earth Pole To Pole

Polar Bear Cubs Photo Credit: Michael Henry

Polar Conduct

Ursus maritimus

Status: Threatened

Clarification

Polar bears are the largest carnivorous land mammals on World. They are about 7 to viii feet long, measured from the nose to the tip of their very short tail. Male polar bears are much larger than the females. A big male can weigh more than i,700 pounds, while a large female person is virtually half that size (upward to ane,000 pounds). Bears can counterbalance about 50 percent more subsequently a successful hunting season than they do at the start of the adjacent; most of this boosted weight is accumulated fat. A newborn polar bear weighs but nearly 1.5 pounds.

Many of the polar bear'southward physical adaptations help it maintain trunk heat and deal with its icy habitat. The bear'due south 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 acquit's fur is actually black; this blackness is evident simply on the nose. Polar bears also have a thick layer of fat beneath the surface of the peel, which acts as insulation on the body to trap heat. This is specially of import while swimming and during the frigid Arctic winter. The bear's large size reduces the corporeality of surface expanse that'due south exposed to the common cold per unit of body mass (pounds of mankind), which generates heat.

The polar carry'southward footpads accept a kind of "non-sideslip" surface, allowing them to get traction on slippery ice. Polar bears have potent legs and big, flattened feet with some webbing betwixt their toes, which helps with swimming and walking on ice. The wide paws prevent sea water ice from breaking by distributing the polar bear'due south weight equally information technology walks. The webbed anxiety results in making polar bears, dissimilar other bear species, considered to be "marine mammals" along with seals, bounding main lions, walruses, whales, and dolphins. Still, they are still bears. The polar conduct evolved 1 to three million years ago from the brown bear, which yet ekes out a marginal life forth the northern shore of the Arctic oceans. Unlike the massive polar bear, which can grow huge on a diet of abundant seals, its ancestor in the Chill is minor, has very lower reproductive rates, and eagerly eats almost annihilation that exists in its surround.

Polar bears have evolved something else that is unlike from their antecedent: most polar bears don't den, however all brown bears exercise. When grizzly comport food is covered in snow during the winter, this species must den because there is zip to swallow. In contrast, about polar bears have access to their food of selection (seals) all wintertime long, so at that place is no need for them to den. The exception to this is meaning adult females. Significant female polar bears must den and then that their tiny newborn cubs are built-in in a warm protected surround; dens tin can exist 38 degrees Fahrenheit warmer than the outside temperature. The cubs would otherwise freeze to decease in the frigid temperatures of the far n.

Range

Most polar bears occur northward of the Arctic Circle to the North Pole. There are some populations south of the Arctic Circumvolve in the Hudson Bay of Manitoba, Canada. Polar bears live in Alaska, Canada, Russia, Greenland, and some northern islands endemic by Kingdom of norway, such as Svalbard.

Polar bears depend on the bounding main ice, which forms above the open waters where their seal casualty lives. They will spend time on land when bounding main ice is not bachelor (and almost 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 bounding main water ice if necessary. All the same, if a storm kicks up during these increasingly long swims (caused past the warming bounding main), they can drown. These long swims and storms are as well oft difficult for cubs. During periods of ice breakup, polar bears oftentimes swim between floating ice islands.

Permanent, multi-year water ice that doesn't always cook is more important to polar bears than the annual ice that melts and reforms every twelvemonth; this multi-yr water ice is increasingly rare, but will likely persist for longer in the island archipelago of northwestern Canada than in Alaska or off the northern coast of Russia.

Diet

Dissimilar other conduct species, polar bears are almost exclusively meat eaters (cannibal). They mainly swallow ringed seals, only may also eat bearded seals. Polar bears hunt seals by waiting for them to come up to the surface of sea ice to breathe. When the seal nears the surface, the polar bear will seize with teeth or take hold of 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, just none of these are arable enough to sustain the big body mass and dense populations of polar bears.

Some other vitally important food source in most areas are seal pups that are born and live in dens in the Arctic ice. The polar conduct 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 bound is increasingly limited by earlier melting of water ice. In the Arctic, polar bears are at the pinnacle of the nutrient chain; they eat everything and aught (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 nutrient source similar 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 hands do.

Life History

Polar bears breed in the late spring as the temperatures begin to ascension in the Arctic. Like other bear species, all the same, they don't really become pregnant at the time of breeding as the tiny embryo (or blastocyst) will not implant in the female'south uterus until autumn, when true gestation starts. This is called delayed implantation and allows a female person bear to physiologically appraise her condition prior to starting gestation and the process of birthing, nursing, and carrying for her offspring for the adjacent iii years. The period of actual gestation following implantation is only about sixty days.

In the Hudson Bay population, where the reproductive biology of polar bears has been near extensively studied, information technology appears that a polar bear female person conveying a blastocyst must achieve a body weight of at least 490 pounds to accept the blastocyst implant and kickoff gestation. If this threshold is not achieved, the blastocyst will reabsorb, the female person will continue to chase seals all winter, attempting to be fatter a year later on and able to conduct off a successful pregnancy.

In the offset of the winter, a meaning female volition dig a den in a snow bank and brainstorm the process of gestation. Depending on the area, pregnant females may enter dens anytime between early October and Dec. The time of exit from dens occurs betwixt belatedly February and April. Most females dig their dens in a snow bank on state, only some also den on the floating sea ice. In Hudson Bay, females may dig a den in the basis instead, but they use areas where the snow will build upward and provide insulation. In the eye of winter in some of the coldest places on Globe, female polar bears requite birth to cubs. Litter size is most commonly two cubs, but sometimes litters can be one, iii, or, very rarely, iv cubs.

Female polar bears in the Hudson Bay area spend remarkable periods of time fasting, the longest known of whatsoever mammal species. This fasting period before denning and in dens averages about 180 to 186 days. In Hudson Bay, significant females can successfully fast for every bit long as 240 days. The long period of fasting makes this species especially vulnerable to ecology changes like a warming climate, which reduces the amount of fourth dimension they have bachelor to build up the fat reserves they need to survive fasting and bring off a successful pregnancy.

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 equally their mother heads out to the ice to catch the seals she needs to replenish the weight she'south lost during her period of fasting. Over the next two years, the cubs will learn from their mother how to grab seals themselves and to develop the other skills needed to survive and abound to adult size. Typically cubs will stay with their female parent until they are two-and-a-one-half years erstwhile, but in some cases they volition stay for a year more or a year less. If the female parent 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 betwixt successive successful litters, and litter sizes are smaller. Polar bears in the wild tin can live to exist xxx years of age, but this is rare. Near adults die before they achieve 25 years.

The conditions developing in Hudson Bay are such that females will no longer be able to nascence and successfully enhance a niggling of cubs. When this happens, the developed bears will survive until they dice of quondam historic period and the population will be doomed. Scientists are fearful that this blueprint is also starting to happen in the more than northern polar bear populations every bit the amount of Chill ice continues to shrink.

Conservation

Polar bears are in serious danger of going extinct due to climate alter. In 2008, the polar behave became the first vertebrate species to be listed under the U.S. Endangered Species Deed as threatened due to predicted climate change. The Secretary of Interior listed the polar behave equally threatened simply restricted the Endangered Species Human action'south protections, and thus the polar carry's future is nevertheless very much in jeopardy.

The principal threat to the polar bear is the loss of its sea water ice habitat due to climate modify. Equally suggested by its specific scientific proper name (Ursus maritimus), the polar carry is really a marine mammal that spends far more than time at body of water than it does on land. It's on the Arctic ice that the polar bear makes its living, which is why climate modify is such a serious threat to its well-being. Polar bears are beingness impacted past climate change in several ways.

Po pulation sizes are decreasing: In southern portions of their range effectually Hudson Bay, Canada, at that place is no sea ice during the summer, and the polar bears must live on state until the bay freezes in the autumn, when they can again hunt on the water ice. While on land during the summer, these bears consume little or nothing. In simply twenty years, the ice-free flow in Hudson Bay has increased by an average of 20 days, cutting short polar bears' seal hunting season by nearly 3 weeks. The ice is freezing later in the fall, merely it is the earlier bound ice melt that is especially difficult for the bears. They take a narrower fourth dimension frame in which to hunt during the critical season when seal pups are born, and average deport weight has dropped by 15 pct. The bears have fewer cubs, and of the cubs they do accept, the frequency of survival to machismo is decreasing. In addition, the interval between successful litters is growing. Every bit a upshot, the Hudson Bay population is down more than 20 pct. The patterns seen in Hudson Bay are first to occur now in more northern populations and is peculiarly well documented on the due north coast of Alaska, but appears to exist the case worldwide.

Bounding main ice platforms are moving farther autonomously: The retreat of ice has implications beyond the obvious habitat loss. Remaining ice is further from shore, making it less attainable. Later on each summer, the trend seen in the Arctic is for sea ice to be further from shore, making it necessary for polar bears to swim increasingly long distances from shore to reach the ice. Worse, the final remaining sea water ice is over deep and unproductive waters that yield less prey. The larger gap of open water between the ice and land as well contributes to rougher moving ridge weather, making the bears' swim from shore to sea ice more than hazardous. In 2004, biologists discovered 4 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 cook in 2011, a female polar bear reportedly swam for nine days nonstop across the Beaufort Sea earlier reaching an water ice floe, costing her 22 percent of her weight and her cub. As climate change melts sea ice, the U.South. Geological Survey projects that 2 thirds of polar bears volition disappear by 2050.

Nutrient scarcity is increasing: As sea ice disappears for longer and longer periods during the late summer, polar bears are left with bereft fourth dimension to hunt. Polar bears tin 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 bug of the loss of hunting areas, information technology is expected that the shrinking polar ice cap will also cause a decline in polar bears' favorite prey—seals. The reduction in ice platforms nigh productive areas for the fish eaten past seals is affecting the seals' nutritional status and reproduction rates. Polar bears are going hungry for longer periods of fourth dimension, resulting in cannibalistic behavior. Although it has long been known polar bears will kill for authorization or impale cubs so they tin breed with the female, outright predation for food was previously unobserved past biologists.

Additionally, development is increasing in sea floor exploration and offshore oil extraction in the open up waters that were previously sealed by frozen ice. This brings people, disturbance, and potentially ruinous oil spills to the previously pristine Arctic polar comport habitat. Polar bears need our help and protection to ensure a long, good for you time to come for the species. The best way for people to aid polar bears is past reducing carbon emissions and working with the National Wildlife Federation to campaign for reductions in climatic change pollutants.

5 Fun Facts

1. Because they spend so much fourth dimension in the ocean, polar bears are classified every bit marine mammals. The polar bear's scientific name, Ursus maritimus, means "sea bear."

2. Polar bears evolved from brown bears to survive in extreme northern environments.

iii. Polar bears are the largest terrestrial predator on the planet, with big males standing more than xi feet (3.3 meters) tall on their hind legs and reaching weights over i,700 pounds (770 kilograms).

4. Unlike blackness bears and brown bears, polar bears do not hibernate during the wintertime months because that's when ocean ice forms, which the polar bears need to hunt seals.

5. When necessary or playing, polar bears communicate with each other with grunts, growls, roars, or squeals. What does a polar bear roar sound similar? We hit the streets to pose this simple question. Hear what people had to say: