Polar bear

Polar bears are the largest species of bear in the world. Compared to other bears polar bears have: a long narrow head; a head that is relatively small compared to the body; small, heavily furred ears; claws that are short and strong; canine teeth that are long; and cheek teeth that are sharper. These features have been selected for in polar bears as a consequence of their almost purely carnivorous way of life. The polar bear has a circumpolar distribution, but is largely restricted to areas that have sea ice during a significant part of the year. Polar bears are typically off-white in colour, but vary from grey, through shades of white to yellow.

Contents

Description

Polar bears are the largest species of bear in the world. They are markedly sexually dimorphic, with males being larger than females. Males weigh between 300–700 kg while females weigh 150–350 kg. The length of adult polar bears varies from 180–260 cm. Weight varies dramatically seasonally, especially among females that can more than double their body weight from the spring to the late summer. Polar bears are typically off-white in colour, but vary from grey, through shades of white to yellow. Adult males can be distinguished from females on the basis of their larger size, but more reliably on their more powerful necks that looks wider than their heads. Compared to other bears polar bears have: a long narrow head; a head that is relatively small compared to the body; small, heavily furred ears; claws that are short and strong; canine teeth that are long; and cheek teeth that are sharper. These features have been selected for in polar bears as a consequence of their almost purely carnivorous way of life.

How to avoid conflicts between polar bears and humans?

From extensive hunting to conservation and research on the king of the Arctic

A hunter fine-tuned for the Arctic

The polar bear’s diet

International polar bear cooperation

Where do polar bears den?

When humans meet polar bears in Svalbard

When scientists head into the polar bear’s realm

We follow the polar bear step-by-step

An invisible enemy

8 December 2020

How to avoid conflicts between polar bears and humans?

8 December 2020

From extensive hunting to conservation and research on the king of the Arctic

8 December 2020

A hunter fine-tuned for the Arctic

8 December 2020

The polar bear’s diet

7 December 2020

International polar bear cooperation

7 December 2020

Where do polar bears den?

3 December 2020

When humans meet polar bears in Svalbard

3 December 2020

When scientists head into the polar bear’s realm

3 December 2020

We follow the polar bear step-by-step

2 December 2020

An invisible enemy

Distribution

The polar bear has a circumpolar distribution, but is largely restricted to areas that have sea ice during a significant part of the year. They live in Canada, Alaska (USA), Greenland, the Russian Arctic, the Norwegian Arctic, and on areas of the ice shelf surrounding the North Pole. They occur as far south as 50° N in James Bay, Canada. There are 19 different defined populations of polar bears in the Arctic, that together contain an estimated 26,000 bears. Individual bears roam over large areas, and populations are therefore well connected.

In Svalbard, most bears are found in areas with sea ice. The western part of Spitsbergen therefore has low densities of bears most of the year, while higher densities are found along the east coast, and also in the fjords to the north. Many bears hunt at glacier fronts in the fjords in the spring because ringed seal lairs are concentrated in such areas. The most important denning areas for polar bears in Svalbard are located on Kongsøya, Svenskøya, Edgeøya, Nordaustlandet and Hopen. In Svalbard, some bears have small home ranges of a few hundred square kilometres where they hunt on the sea ice in the spring; during summer these bears wait on land for the sea ice to freeze again. Other bears follow the retreat of the sea ice and move north-east or east in the summer, hunting at the ice edge or in Franz Josef Land in Russia. The Barents Sea population of polar bears includes animals that den in both Svalbard and Franz Josef Land. Movement westwards to Greenland, or from Greenland to Svalbard, seem to be quite restricted.

General ecology

A survey of the Barents Sea polar bear population, conducted in August 2004, concluded that there are between 1,900 and 3,600 polar bears in this region. Approximately half of these animals may reproduce in Svalbard. Polar bears are powerful swimmers. Their most important prey by far is ice-living seals, so they spend a lot of their time on the sea ice. Adult bears can spend days at a time in the water and travel very long distances at sea.

In Svalbard, their main prey species are ringed seals, bearded seals and harp seals. However, polar bears are opportunistic feeders and eat almost everything edible that they encounter — including carrion. Some bears take a lot of bird eggs in the summer. Polar bears also hunt sea birds even in steep cliff areas. Predation on reindeer has been recorded occasionally. Stranded corpses of dead whales can attract large numbers of scavenging bears. Polar bears are largely solitary, except for mothers with their young or male-female pairs that are together during brief periods in the mating season. Only pregnant female polar bears den during the winter; all other polar bears are winter active, even during the months with 24 hour darkness. Non-pregnant bears will dig day-beds in the snow in which they rest for a day or two at a time, and in some cases temporary dens where they can stay for days or weeks, e.g. in periods with bad weather.

Life history and reproduction

Polar bears mate in April or May. At this time of year, males track the smell of females that can be many kilometres away. Females in Svalbard usually mate for the first time when they are five years old. Males reach sexual maturity somewhat later and do not reach full body size until they are 8–10 years old. A large male can mate with several females within the same season, attending each for some days or weeks. Polar bears have delayed implantation; the egg does not begin to develop beyond some few initial steps before the autumn (September–October), although the female mates in the spring. A pregnant female builds a birthing den in late autumn which she enters for about four months. During her time in the den she goes into a winter sleep, dropping her metabolic rate and her body temperature to conserve energy.

Females give birth around New Year. The cubs are very small (approximately half a kilo) when they are born. Most frequently polar bears have two cubs in a litter, but litter size ranges from one to three. Polar bear milk is rich in fat, and the nursing cubs grow quickly in the security of the den. They weigh about 10 kg when the family leaves their winter home in late March or early April. Juveniles follow their mother until the age of 2.5 years, at which time the mother is ready to mate again. Survival of juveniles is low, with only about one out of three reaching the age of two years. Adults have high survival, and typically live to be 15–25 years old.

Isbjørnens utfordringer

Klimaendringer og mindre havis

Sen ankomst av sjøis rundt tradisjonelt viktige hiområder som Kongsøya og Hopen på høsten har i mange senere år ført til at få binner har nådd øyene for å gå i hi. I mildere år fødes færre unger i disse områdene enn i kaldere år, og vi vet at mange år med lite havis kan føre til lav overlevelse, særlig blant unge dyr. Det er likevel usikkert om dette har ført til reduksjon i bestandsstørrelse, eller om bestanden fortsatt er i vekst.

Isbjørnene på Svalbard viser responser på klimaindikatoren Arktisk Oscillasjon (AO). Og om klimaet fortsetter å varmes opp i Arktis, med medfølgende tap av sjøis, vil bestanden utvilsomt bli påvirket negativt.

Forurensing og miljøgifter

Studier har vist at isbjørn har høye konsentrasjoner i fett og blod av fettløselige miljøgifter (bl.a. PCB og bromerte flammehemmere). Miljøgifter konsentreres oppover i næringskjeden, og dyr på toppen av har derfor de høyeste verdiene. Isbjørn er helt øverst i næringskjeden, og på grunn av at Svalbard tilføres miljøgifter både via luft- og havstrømmer har isbjørn i europeisk Arktis spesielt høye nivåer av langtransporterte fettløselige miljøgifter.

Miljøgifter har innvirkning på isbjørnenes hormonnivå og immunsystem. Høye nivåer av miljøgifter – i kombinasjon med lavere mattilgang i et varmere klima – kan gi arten store problemer i framtiden. Miljøgifter som er lagret i fettet frigjøres i blodet når dyret sulter. Dette omfatter også tiden ungene ligger i hiet og dier, siden binna da ikke tar til seg næring. Isbjørnmelken er svært fettrik, og ungene blir derfor spesielt utsatt for høye miljøgiftkonsentrasjoner.

Sult

Trolig er sult den viktigste dødsårsaken hos isbjørn. En tilleggsbelastning etter perioder med matmangel og forbrenning av fettreserver er at fettløselige miljøgifter kommer i blodbanen der de kan gjøre skade.

Parasitter kan også spille en rolle. På Svalbard er det særlig to parasitter, trikiner og toxoplasma, som er svært vanlig hos isbjørn. Foreløpig vet vi lite om virkningen av disse parasittene på bjørnene, men det kan tenkes at de fører til sykdom.

Menneskelig aktivitet

Mindre is gjør områdene mer tilgjengelige, både for turisme og transport, samt olje- og gassutvinning. Økt menneskelig aktivitet i arktiske områder kan være negativt for arten. Farlige situasjoner i møter mellom isbjørn og mennesker oppstår jevnlig på Svalbard. Økning i skipstrafikk og petroleumsvirksomhet betyr økt miljørisiko i området, og risikoen for akutte oljesøl øker tilsvarende.

Isbjørnforskning

Etterspørselen etter kunnskap om isbjørn er stor, og det har lenge vært intens forsknings- og overvåkingsaktivitet blant verdens isbjørnnasjoner.

Norsk Polarinstitutt har drevet forskning på isbjørn i norsk Arktis siden 1960-årene, og norske isbjørnforskere har tilegnet seg mye kunnskap om arten. Vi har også en av de lengste kontinuerlige dataseriene på isbjørn, innhentet med fangst-gjenfangst-metodikk (fra 1987), noe som muliggjør en rekke ulike studier på arten.

På Svalbard prioriteres nå forskning på miljøgifter, sykdom, demografi og effekter av klima. Mellom 50 og 100 isbjørn merkes eller gjenfanges hvert år. Fra disse tas det prøver for ulike analyser, og flere merkes med satellittsendere som forteller hvordan de vandrer gjennom året.

I de kommende år vil det være spesielt fokus på hvordan isforhold påvirker antallet reproduserende hunner og overlevelse av isbjørn i ulike aldre.

Management status and monitoring

The need to streamline and coordinate the circumpolar monitoring of polar bears is becoming increasingly important. This will place higher demands on international coordination and cooperation than we see in current activities.

Norway signed the Polar Bear Agreement in 1973, together with Canada, Denmark (Greenland), the USA and Russia. These countries manage the world’s polar bear populations, and in recent years have met more often than before, due to the serious threats the species faces.

After the agreement was signed in 1973, ratified in 1976, and reaffirmed in 1981, the parties did not meet until the United States requested an informal meeting in 2007. At this meeting, Norway, as a signatory to the agreement, was asked to convene the parties again. The first official party meeting after 1981 was held in Tromsø in March 2009, and here the nations agreed to start the development of an action plan, and to meet every two years. Party meetings have subsequently been held in Iqaluit in 2011, in Moscow in 2013, in Greenland in 2015, where a final action plan was approved, in Alaska in 2018, in Longyearbyen on Svalbard in March 2020, and most recently in a virtual meeting in November 2023.

According to the Polar Bear Agreement, Norway is obliged to: “take appropriate action to protect the ecosystems of which polar bears are a part, with special attention to habitat components such as denning and feeding sites and migration patterns, and shall manage polar bear populations in accordance with sound conservation practices based on the best available scientific data». According to the agreement, the countries have undertaken to protect the polar bear’s habitats, but there has been a challenge in following up on this agreement when it comes to protecting important sea areas in international waters.

The administrative authorities provide for strict restrictions on traffic and other human activity in den areas and other important living areas in Norwegian waters. The need to streamline and coordinate the circumpolar monitoring of polar bears is growing. This will place higher demands on international coordination and cooperation than we see in current activities.

Hunting

In Svalbard, the polar bear was subjected to harsh hunting and trapping for a hundred years, but after 1973 polar bear hunting in this area has been illegal (see capture statistics for polar bears in Svalbard).

The population has recovered significantly since the protection 40 years ago. Up to three bears are typically shot each year in Svalbard in self-defense or euthanized due to damage to property. Despite the number of encounters between bears and man likely have increased in recent years concomitant with increased human traffic within the archipelago, the number of bears killed have dropped in recent years.

In Canada, Alaska and Greenland, approximately 700 polar bears are shot annually. Polar bear hunting is illegal in the Russian Arctic, but an unknown number of polar bears are still shot there every year.

Polar bear

Description

How to avoid conflicts between polar bears and humans?

From extensive hunting to conservation and research on the king of the Arctic

A hunter fine-tuned for the Arctic

The polar bear’s diet

International polar bear cooperation

Where do polar bears den?

When humans meet polar bears in Svalbard

When scientists head into the polar bear’s realm

We follow the polar bear step-by-step

An invisible enemy

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