A warming world means that sea ice is melting earlier and forming later every year. Polar bears thus have less time to hunt for food, and female polar bears have less time to build up the fat reserves essential for when they hibernate and give birth.
This also leads to lower reproductive rates, as undernourished bears have fewer cubs.
Ongoing exploration for oil in the Arctic has a number of consequences for polar bears, including:
• Habitat destruction
• Disturbance (seismic blasting, construction, boat traffic)
• Oil pollution (poisoning, oil spills, etc.)
Polar Bear Basics
1 Their latin name, Ursus maritimus, means “sea bear”
2 Polar bears are the largest land-based carnivores in the world. Adults can grow to over 2.5 metres long and weigh almost 700 kilos!
3 Most of their life is spent on sea ice and in the water. They are easily able to swim at speeds of around 10 kilometres an hour
4 Polar bears have been spotted swimming more than 100 kilometres from land
5 They have incredible adaptations to their environment, including huge, webbed paws, a streamlined skull and long neck for swimming, and thick blubber for insulation and buoyancy
6 Their diet consists mainly of seals, which they hunt from the sea ice, ambushing breathing holes. They also feed on walruses, beluga whales, whale carcasses, and seabird eggs
7 Polar bears have in incredible sense of smell – they are able to detect prey from many kilometres away
8 Individual bears may travel thousands of kilometres each year to find food
9 Polar bears are generally solitary animals, except when breeding or rearing their cubs
10 Polar bear fur isn’t really “white”. It is transparent with a hollow core that reflects the light
- Polar bears normally mate from late March to May
Gestation is around eight months
Pregnant polar bears will seek out maternity dens, in October or November, in which to hibernate and then give birth to their cubs. Pregnant polar bears need to build up fat reserves to survive the “denning period”
Cubs are born from November to January while the mothers are hibernating
Sows can have up to four cubs at a time, though one or two is more common
Cubs weigh about two kilos when they are born, and will nurse until they reach about 10 to 14 kilos before emerging from the den in March or April
Cubs will stay with their mothers for a little over two years
Female polar bears can produce five litters in their lifetime
Polar bears have one of the lowest reproductive rates of any mammal
With such low reproductive rates, as well as a high degree of specialisation to a vulnerable ecosystem, polar bear populations are extremely vulnerable
The World Conservation Union (IUCN) estimates that there are between 20,000–25,000 polar bears in the world
Polar bears are distributed throughout the Arctic region in 19 subpopulations. They are found in Alaska, Canada, Russia, Greenland and Norway.
The most important habitats for polar bears are the edges of pack ice, where the melting and refreezing of ice creates patches of ice and patches of water where they can find the greatest number of seals