Description and Ecology
Polar bears are very well known. They live in the arctic and inhabit habitats such as the forest, marine oceanic and marine intertidal. They are K-selected species, meaning they do not have low quantities of offspring and late sexual maturity. Their reproductive rate is actually among the lowest in all mammals. But their maternal investment is very high and the adult survival rate is too.
Polar bears are also the most carnivorous of existing bear species. They feed on ringed seals, bearded seals, harped seals, hooded seals and they have been know to prey on larger species such as walrus. They are able to survive off these prey because of the way they digest fats. Polar bears are able to digest fat much better than proteins. And since seals and similar animals are covered in fat (due to their use of it for swimming in the freezing arctic oceans) polar bears strive off these prey. However, due to this dependence on fat they would likely starve on a primarily terrestrial diet.
Geographic and Population Changes
Currently the species range is as shown in the map above. They cover most of the arctic circle and part of Canada, Alaska Russia and Greenland. Yet this is rapidly changing due to climate change the land they live on is quickly melting. The current population of polar bears is unknown. However it is known to have declined from its historic population numbers. Due to climate change there has been a rapid increase in the temperatures around the world. And in the arctic this means glaciers are melting, and the land that inhabited the polar bears is decreasing. Not only that but it is being broken apart, this is known as free ice. Where larger land masses break apart due to the change in climate. This now separates polar bear communities and again leaves them with smaller habitats. But the effect on polar bears is also indirect. The loss in land of course affects other other species that use it, like seals. Seals use this land to raise their young, and with the loss of it their population of seals declines and in turn many polar bears no longer have their main food source.
The Polar Bear Specialist Group (PBSG) of the International Union for the Conservation of Nature recognizes 19 subpopulations of polar bear. One of the subpopulations has increased, six has remained stable, three have declined and the other nine lack the data to come to a consensus. The reason behind such little information is that collecting data on polar population is incredibly expensive and difficult with species that occur in such remote areas and at low densities. However with the current information there is an estimated total of 26,000 polar bears.
Listing Date and Type of Listing
Polar bears have been assessed and are listed as "vulnerable". They were assessed on August 27, 2015. Climate change caused a decrease in populations. The assessment means that polar bears are considered to be facing a high risk of extinction.
Cause of listing and main threats to its continued existence
The main threat, and a huge theme in this blog, is climate change. They are dependent on the ice for their prey and for their dens. However, the increasing climate has also led to more diseases to occur among polar bears. The warming climate has been connected to an increase in pathogens to both terrestrial and marine arctic species. Parasites that are more inept to developing in warm blooded hosts benefit greatly from the changes in temperature. Many of these pathogens have already been found in seals, which are the main prey of polar bears.
Another threat to polar bears is also the pollution in the waters they swim in. Despite living in the arctic much of the toxic runoff from industries still make their way to the water the bears inhabit. Polar bears also feel the effect of pollution from the animals they prey on. Since polar bears are apex predators they ingest the accumulation of pollutants that occurs along the food web. This is known as bioaccumulation. Another form of pollution that is hurting the polar bears is from oil development in the arctic. Resource exploitation increases the ice breakage. There is also in increase of human interaction with the bears but even bigger than that is the threat of oil spills and waste from the industrial work going on in their habitat. The oil spills in the ocean are a danger to seals which are their main prey. But the waste on land is dangerous for the polar bears, since they are known to ingest plastics, styrofoam, lead acid batteries, tin cans, oil, and other hazardous materials. Polar bears are also being hunted for clothing, meat and other of their resources. Yet the harvest of polar bears is legal, and is even thought to be sustainable in most subpopulations.
Recovery Plan
Currently there is no action recovery plan. Yet there is land/water protection and species management, as well as education actions that are taking place. In 1973 The International Agreement on the Conservation of Polar Bears was signed. Article II of this agreement states that each party “…shall manage polar bear populations in accordance with sound conservation practices based on the best available scientific data,…”. In addition Article IV states “The Contracting Parties shall conduct national research programs on Polar Bears…” and “...consult with each other on the management of migrating Polar Bear populations...”. Due to the increase in dangers the polar bears are facing the Parties have agreed to set into motion a plan to lead into a coordinated approach of conservation and management strategies. The Circumpolar Action for Polar Bears was signed in 2015. With this the parties conduct national research programs for the polar bears and monitoring the harvests and other removals of the bears. They also set out to understand the movement patterns and how they relate to habitat change. They document human-bear interactions and conflicts, trends in habitat use, and pollution and disease.
What can you do?
Use cars less
Use energy efficient lightbulbs (LEDs)
Recycle
Turn off electronics when you are not using them
Doing anything to decrease your carbon footprint will help the polar bears not lose the ice they so depend on. And it will do a great number of other organisms good too.
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