Number 91 Mummy Polar Bear sleeping wid her cubs

The polar bear (Ursus maritimus), also known as the white bear, northern bear, sea bear, ice bear or nanuq in some Inuit languages, is a species of bear that is native to the Arctic and the apex predator within its range. Its thick blubber and fur insulates it against the cold,and its translucent fur camouflages it from its prey, This fur is commonly mistaken as white or cream-colored due to the way light refracts within each hair. The bear has a short tail and small ears that help reduce heat loss, as well as a relatively small head and long, tapered body to streamline it for swimming. The polar bear is a semi-aquatic marine mammal that depends mainly upon the pack ice and the marine food web for survival. It has uniquely adapted for life on a combination of land, sea, and ice and is now dependent on this combination.[2]
Scientists and climatologists believe that the projected decreases in the polar sea ice due to global warming will have a significant negative impact or even lead to extinction of this species within this century.[1][3]
An alternative theory downplays the affect climate change is having on the polar bear and hypothesizes that the species may survive through adaptation.

Polar bears rank with the Kodiak bear as among the largest living land carnivores, and male polar bears may weigh twice as much as a Siberian tiger. There is great sexual dimorphism, with some males reaching more than twice the size of the females. Most adult males weigh 300-600 kg (660-1320 lbs) and measure 2.4-3.0 m (7.9-10.0 ft) in length. Adult females are roughly half the size of males and normally weigh 150-300 kg (330-660 lbs), measuring 1.9-2.1 m (6.25-7 ft).[5][6] At birth, cubs weigh only 600-700 g or about a pound and a half.The polygamous polar bears mate in the spring (March to May); pairing only lasts for the actual mating with few permanent bonds observed. Testosterone levels increase in the spring for the males and the testicles increase in size.[citation needed] Once fertilized the females ova undergoes a delayed implantation, which takes hold in September or October. The gestation period is between 195 and 265 days (about 8 months) with the cubs born soon after the ova implant in early winter (November to December). The mother digs a two-chambered cave in deep snow for the birth in October after a period of heavily feeding. Usually, two cubs are born, less often one or three; litters of four cubs have been recorded. Like other Ursus bears, the new cubs are tiny, typically 30 cm long and weighing 700 g (a pound and a half), compared to their sometimes 300 kg (660 lb) mothers. The helpless and blind cubs open their eyes after about a month, emerge from the den at about 10 kg (22 lb), are able to walk at 1.5 months, and start eating solid food at 4-5 months. They remain with their mother, learning to hunt and protect themselves against adult males, which sometimes cannibalize cubs. Females nurse their young for up to two and a half years on milk that contains approximately 33% fat, higher than that of any other species of bear and comparable to that of other marine mammals.[8] The bears farther north tend to stay longer with their young, with weather conditions and age of the female affect this time as well. Sexual maturity is reached at 3-4 years. Adult polar bears are known to live over 30 years in captivity with average around 25. In the wild this is likely much shorter. Polar bears do not hibernate, though lactating females go into dormancy during denning. The female can control urea cycling so she can endure a long fast during this time[citation needed]; they often go without eating for a period of nine months and rely on stored body fat (also known as blubber) to keep themselves and their cubs alive. Once the cubs mature they go their separate ways.
The 2004 National Geographic study found no cases of cubs being born as triplets, a common event in the 1970s, and that only one in twenty cubs were weaned at eighteen months, as opposed to half of cubs three decades earlier.[21]
In Alaska, the United States Geological Survey reports that 42 percent of cubs now reach 12 months of age, down from 65 percent 15 years ago.[27] In other words, less than two of every three cubs that survived 15 years ago are now making it past their first year.