Polar bear

Published by the Norwegian Polar Institute

Polar bears (Ursus maritimus) are found throughout the Arctic, including the Svalbard archipelago and the surrounding sea ice. The species is the world’s largest terrestrial carnivore. Polar bears hunt mainly from the sea ice, and have difficulty finding enough food when there is no ice cover. Climate change and pollution are the most serious threats to polar bears.

Almost 3000 polar bears in Svalbard and the Barents Sea

There are about 20 000–25 000 polar bears in the world, unevenly distributed throughout the Arctic. Satellite tracking shows that there is a joint Norwegian-Russian subpopulation around Svalbard and the Barents Sea. In 2004, it was estimated that there were almost 3000 polar bears in this region. A new survey of the joint Rusian-Norwegian population is planned to take place during August 2015. 

Polar bear dens have been studied on the island of Hopen (southeast of Spitsbergen) and certain other areas of Svalbard. The number of dens on Hopen appears to fluctuate depending on the timing of ice formation in autumn. There are fewer dens in years when the ice cover forms late in the season than in years when it forms early. Because of this link with climate change and its impacts, there is now a permanent monitoring programme for polar bear dens in Svalbard.

There are eight species of bears across the world, but only the polar bear is entirely carnivorous, feeding mainly on seals. Hunting behaviour and the area used as a home range vary widely. Some polar bears roam across an area as large as mainland Norway. On the other hand, tagging of female polar bears from Storfjorden between the islands of Spitsbergen and Edgeøya has shown that they remain in this area and do not roam across the Barents Sea.

Sea ice loss causing great concern

Environmental conditions in the Arctic are highly variable, which results in a wide range of variation in many of the biological systems in the region as well. This makes it difficult to distinguish between natural variation and variation caused by human activity.

Polar bears dependent on melting sea ice

Many climate models predict a dramatic loss of sea ice during the present century. In the last few years, observations have shown a clear reduction in ice cover in almost all parts of the Arctic. Climate models indicate that it will only be a few decades before the entire Arctic Basin is ice-free in summer.
 
In 2007, researchers from the US Geological Survey modelled sea ice and the likely response of the polar bear population to a dramatic reduction in ice cover. Their studies showed that we could lose two-thirds of the world population of polar bears by 2050. Time will show whether this happens, but there is general agreement that ice cover will continue to decline. Polar bears are highly dependent on ice cover, since they hunt mainly from the ice. Their most important prey species, ringed seal and bearded seal, are perhaps even more strongly associated with the sea ice. The polar bear is at the top of the Arctic food chain, and will therefore rapidly be affected by changes in the populations of prey species.

High levels of pollutants in polar bears

It has been documented that polar bears carry high loads of persistent organic pollutants (POPs), and that these pollutants affect bear health. Concentrations of new types of pollutants, such as brominated flame retardants and fluorinated compounds, are rising in polar bears, whereas there is a general decline in levels of “old” POPs such as PCBs and DDT in the Arctic.

Nevertheless, the PCB levels measured in polar bears in Svalbard are so high that they are liable to cause effects such as:

  • disruption of the hormonal system
  • damage to the immune system
  • reduced reproductive capacity
  • lower life expectancy for adults
  • higher cub mortality.

These effects could in turn reduce survival or cause rapid population decline because of disease. However, we do not yet know enough about how POPs are actually affecting polar bear reproduction or population size.

Milder climate and pollutants the main threats

Climate change is perhaps the greatest threat to the survival of the polar bear. Global warming is resulting in loss of ice cover, and ice is forming later in autumn and melting earlier in spring. This shortens the bears' hunting season and results in a loss of habitat for both bears and their prey species. In addition, migration patterns and access to denning areas are affected. Snow quality also changes, making it more difficult for polar bears to find snow of a suitable type for constructing dens.

Pollutants

Polar bears’ main prey is seals, and they eat large quantities of seal blubber. This is why polar bears are so vulnerable to fat-soluble pollutants, which accumulate in fatty tissue. PCB levels in polar bears are higher than those found in other Arctic species, and levels in polar bears from Svalbard are higher than those measured in bears from Canada and Alaska. Recent sampling suggests that polar bears in the eastern Barents Sea and the Kara Sea are the most heavily polluted in the world, closely followed by polar bears from Svalbard.

Climate change is expected to influence the transport, spread and uptake of POPs and mercury in polar bears.

Hunting

The polar bear is protected throughout the Arctic, but Inuit communities in North America and Greenland are allowed to take a limited harvest. Hunting is strictly regulated, and quotas should only be set if enough is known about the subpopulation to document that the harvest is sustainable. Despite this, quotas are still being set for some areas where too little is known, for example eastern Greenland. No hunting is permitted in Svalbard.

Polar bears are occasionally killed illegally in northwestern Russia, which may mean that Svalbard’s polar bears are the last remaining large carnivore population anywhere in the world that is not harvested.

International interest in polar bears

All the polar bear range states (Greenland (formerly Denmark), Canada, the US, Russia (formerly the Soviet Union) and Norway) are parties to the 1973 Agreement on the Conservation of Polar Bears. The agreement bans the hunting, killing and capturing of polar bears, with the exception of a limited quota for indigenous peoples, and forbids sales of skins and other polar bear products. It also requires the parties to conduct research and monitoring as a basis for managing polar bear populations.

In 2006, the International Union for Conservation of Nature (IUCN) changed the status of the polar bear on the IUCN Red List to “vulnerable” on the basis of evidence suggesting that a population reduction of more than 30 % is likely within three generations (45 years). Since then, several countries have adjusted their polar bear management regimes. The species was already strictly protected in Norway.

In response to the strong international interest in polar bears, the parties to the Polar Bear Agreement have agreed to hold more regular meetings. There had been no meeting since 1981, but at an informal meeting in 2007 they agreed to organise a Meeting of the Parties every other year. The first of these was held in Tromsø in Northern Norway in March 2009, and later at Iqaluit in Canada in October 2011 and in Russia in December 2013. The next meeting is going to be held in September/October 2015 at Ilulissat in Greenland.

Monitoring polar bears in the Barents Sea

The Norwegian-Russian polar bear subpopulation in the Barents Sea is continuously monitored, and there are ongoing research programmes. The new Norwegian-Russian survey planned in 2015, will hopefully provide a better basis than we have now, for assessing whether the stock grows, is stable or declining.

The polar bears are monitored by mark-recapture studies, and information is being obtained on the number of cubs born and cub survival. One method used to find out more about how widely polar bears range and how they use their habitat is to fit them with satellite radio collars. Between 1988 and 2012, 245 female polar bears were fitted with these devices. Blood and fatty tissue samples are taken at the same time. In addition, ice conditions around Svalbard are monitored to provide information on how much the polar bear habitat and hunting conditions are altering as the climate changes.

The current monitoring programmes have given us early warning that pollutants are a significant stress factor for polar bears. However, without further surveys that provide a good enough statistical basis for determining whether the population size is changing, it is not possible to tell whether the number of polar bears in the Barents Sea areas is actually being affected.