Thousands of Earth Rangers are taking action to protect the Polar bear
Details: Through the help of kids just like you, Earth Rangers, the Churchill Northern Studies Centre and Polar Bear Scientist Dr. Nick Lunn are protecting the Polar bear. The donations raised for this Bring Back the Wild™ project are helping to:
- Support scientists in their fieldwork, which will help us learn more about what Polar bears eat, their movement patterns, and reproductive habits
- Purchase satellite collars to place on Polar bears so we can track them and learn more about how early melting of sea ice due to climate change is impacting their offshore movements, survival and health
A message from researcher Dr. Lunn…
Polar bears live on the sea ice in the winter throughout the circumpolar Arctic, which they use for travel and as a platform to hunt seals. However, the Arctic is warming, causing more and more of the sea ice to melt. For animals, like Polar bears, that are dependent on sea ice to survive, there is great concern for their future. I am very pleased to be partnering with Earth Rangers to study this magnificent animal and help Bring Back the Wild in Canada’s North!
Check out the latest updates about the polar bear!
- Polar bears are the largest terrestrial carnivores in the world, growing up to 600 kg
- They live on Arctic sea ice(December-July) butmove onshore when the ice melts in the summer (August-November)
- They hunt ringed seals and mostly eat their blubber; meat they leave behind is vital to the survival of other Arctic animals (e.g. Arctic fox)
- They catch seals by waiting at their breathing holes and grabbing them when they come up for air
- Females mate in April or May on the ice and move onto land in August to den; pregnant females live off their body fat until they emerge from dens with their 3-month old cubs and return to the ice to feed.
- Polar bears are classified as vulnerable (IUCN, 2008), special concern in Canada (COSEWIC, 2008)
- Global warming and bioaccumulation of toxins are their main threats
Polar bears are the largest land carnivore in the world, and, along with Kodiak bears, are the largest bears on Earth. Adult males can weigh up to 600kg and measure about 2.6m in length – that’s about the same size as a small car, and almost twice as heavy as a Siberian tiger!
Although born on land, Polar bears spend much of their time in and around water. They have thick fur and lots of body fat to keep them warm in the harsh Arctic conditions, and have large furry paws that act as snowshoes on land and flippers underwater. To give them better grip on icy surfaces, the pads of a Polar bear’s paws are covered in soft little bumps called papillae, which give them better traction like how big treads on snow tires help cars stay on the road in the winter. Their neck and forelimbs are quite long which they use to hunt seals through holes in the ice. Their powerful hindquarters help them to lift their prey on to dry land.
Polar bears have a reputation for being extremely aggressive, but they are not territorial animals and young will sometimes play with each other when they meet. They are curious animals and have been known to come close to humans. For the most part, Polar bears will not attack humans when they are well fed from seal hunting, but because of their large size and unpredictability when hungry, people living in the Arctic know to give these bears plenty of space.
Polar bears are often found along the coastal areas of the Arctic, including parts of Greenland, Norway, Russia, the United States and Canada, with about two-thirds of their total population living in Canada (15,500 bears).
Their preferred habitats are packs of ice in the shallow waters of the continental shelf because that’s where they can best hunt for ringed seals that make up most of their diet. Throughout the year, the sea ice will change in shape and extent in response to the seasons, causing the seals to move around the Arctic Circle. Polar bears will try to move with their prey as best they can, however, during the summer when the ice melts they either have to retreat northwards on the ice to colder climates or move inland until the next freeze-up, depending on the location of the population. Since they depend so much on the sea for their survival, Polar bears are considered to be marine mammals even though they live on land for part of the year when the sea ice is not available.
The timing of when Polar bears are on land versus out on the Arctic sea ice differs between pregnant and non-pregnant individuals. Polar bears generally live on Arctic sea ice (December-July) and then move onshore in August when the ice melts in the summer, returning to the ice in November for another winter. When other adults and older cubs are returning to the sea ice, pregnant females remain on land in dens to give birth to their young and don’t return to the ice until the following February/March to feed.
Polar bears require specific resources and environmental conditions to survive. Generally, they only eat seals, capturing them by either pulling them up through breathing holes in the ice, crouching and walking slowly up to seals on the ice, or by swimming through channels or cracks in the ice. Polar bears are dependent on seal populations as their main prey. Polar bears are apex predators, meaning they have no natural predators once they reach adulthood. Northward shifts of ecosystems due to climate change have resulted in a rise in aggressive encounters between adult Polar bears and Brown bears. There are also cases of Polar bear cubs being preyed upon by wolves or Brown bears.
While adult Polar bears may not be prey themselves, they provide food for other animals in their ecosystem. For example, when Polar bears catch seals they typically eat only the fatty blubber and leave the meat behind because the blubber’s fat content has the highest caloric content and helps them survive the frigid cold Arctic winter. These seal carcasses are invaluable to other animals in the Arctic ecosystem because they provide food for young Polar bears and scavengers such as Arctic foxes and gulls.
A Polar bears’ diet is made up almost entirely of seals. Most often, Polar bears will catch ringed seals but they will sometimes eat bearded seals or harp seals as well. Polar bears have also been known to hunt for walruses, belugas or narwhals, but preying on these species is very rare due to the risk of injury. An adult walrus can weigh twice as much as an adult Polar bear and can cause serious injuries with its 1 m long ivory tusks; a Polar bear will usually only try to attack a walrus under near-starvation conditions.
Since Polar bears arenot the most graceful runners and overheat easily, they have developed a clever technique to make their prey come to them. Ringed seals can’t breathe under water so they have a network of breathing holes in the ice. Polar bears will wait at these breathing holes, and,when a seal comes up to catch a breath, will useits powerful paws to pull them up onto the ice. Polar bears have also been known to smash into birthing lairs of seals to eat newborn young, or even stalk seals basking in the sun on the shore.
During the summer, when the sea ice melts away from the shorelines, some bears migrate to land to wait for the next freeze-up in late fall. Since they can’t get seals during this time, they mostly have to rely on the fat they built up over the winter. This lag in being able to hunt is why it is so important for them to bulk up on seal blubber during the winter and spring. During the summer, hungry Polar bears sometimes eat carcasses, and when really desperate they will feed on grasses and berries. Some Polar bears have even been seen trying to catch seabirds by swimming out in the water and popping up underneath them!
Polar bear populations grow very slowly because females usually have no more than two cubs at a time and only breed every three years or so.
The mating season takes place in April and May on the ice before ice-break up. During breeding, bears from different populations can mate with each other because populations overlap on the ice. The bears move onto land in August as the sea ice melts. As fall progresses, females begin seeking out deep snowdrifts that they can use for their dens. Denning areas do not overlap with other Polar bear populations’ denning locations. The dens are dug into the snow, with a long tunnel that leads into one of three large chambers where the mother will give birth and nurse her young. Pregnant females give birth to, on average, two cubs from late November to early January. Mothers live off their body fat until they emerge from their den with their 3-month old cubs, about eight months after coming onshore (February or March), at which time they return to the ice with their cubs to feed.
The cubs are helpless at birth. They are blind, measure only about 25cm long, weigh less than a kilogram and are covered in fine, downy white fur. For the next month or two the mother will continue to stay with her young to protect and nurse them. As a result, mothers cannot go on hunts and have to survive off the fat they built up before they began to den. Polar bear cubs weigh approximately 10-15 kg at three months of age.
The cubs depend on their mother for survival for the first two or three years of life. The first year of a Polar bear’s life is its most vulnerable; female Polar bears can be fearless when protecting their young!
- Globally vulnerable (IUCN, 2008) and a species of special concern in Canada (COSEWIC, 2008)
- Main threats include Arctic sea ice habitat loss and changes in food availability due to climate change, and bioaccumulation of pollutants
Polar bears are currently listed as vulnerable globally, and are a species of special concern in Canada. These magnificent creatures face many threats in the wild including habitat loss, limitations in food availability, which affects their health and pollution.
Polar bears rely heavily on sea ice for travel and hunting so climate change poses an enormous threat to this species. As the climate of our planet warms, Arctic sea ice is breaking up earlier in the summer and becoming thinner and timing of freeze up the following winter is also being affected. These threats are changing Polar bears’ movement patterns and ability to find large ice sheets to use as hunting platforms for seals. Reduced hunting opportunity is hurting Polar bear health. Scientists warn that the loss of Arctic ice hunting grounds could prove devastating to Polar bears.
Furthermore, seals and fish are being contaminated by pollutants washing into the sea from industry. As Polar bears consume more and more of these contaminated animals, those same chemicals start to build up in the bears’ insulating body fat, a process called bioaccumulation. As toxin levels continue to increase in their bodies, the Polar bears can become weaker and more vulnerable to disease.
In the past, Polar bears have been able to survive changes in their climate, but those changes occurred at a much slower rate than what we are seeing now. We do not know if Polar bears will be able to continue adapting to climate change. Our actions have huge and far-reaching impacts; with chemicals that we release into the environment, thousands of kilometers south of the Arctic, being found in Polar bear tissues. What we do at home is affecting the lives of animals in some of the most remote parts of our planet.
Cook et al. (2007). Examining the population viability of the polar bear (Ursusmaritimus). Journal of Conservation Biology 3065 Vol. 1:30-40.
DerocherAE, NJLunn, and I Stirling (2004). Polarbears in a warming climate. Integrative and Comparative Biology 44:163-176.
Lunn et al. (2010). Polar bears. Arctic Biodiversity Trends 1:26-28.
McKinney et al. (2010). The role of diet on long-term concentration and pattern trends of brominated and chlorinated contaminants in Western Hudson Bay polar bears, 1991-2007. Science of the Total Environment 408:6210-6222.
Species at Risk Public Registry.Polar bear.
IUCN Red List of Threatened Species.Ursusmaritimus.
Hinterland’s Who’s Who. Polar bear.