Just don’t look for them in the Antarctic…!
On Thin Ice
The first polar bear I ever saw had a large number 59 painted on its rump - and that was in Spitsbergen…!
Not a great start to the trip, but it soon improved, and we ended up having around 13 polar bear sightings.
Spitsbergen (or Svalbard) is one of the best places to go to see polar bears, but cruises are generally scheduled in the summer months when the days last 24 hours, so you might want to go to Canada if you want the warmer light at sunrise and sunset.
If you want a few tips on how to shoot a polar bear, just take a look at my blog post.
Basic facts
Order: Carnivora
Family: Ursidae
Species: Polar bear (or nanook)
Scientific name: Ursus maritimus
Subspecies: none
Mass: 350–700 kg (770–1,540 lb) for adult males, 150–250 kg (330–550 lb) for females.
Height at shoulder: 122 to 160 cm (4 ft 0 in to 5 ft 3 in)
Length of head and body: 2.4–3 metres (7 ft 10 in–9 ft 10 in) for adult males, 1.8–2.4 metres (5 ft 11 in–7 ft 10 in) for females
Appearance: Bear with sharp teeth and claws, thick, whitish or yellowish fur and a short tail.
Top speed: 40 km/h (25 mph)
Gestation period: 195 – 265 days
Lifespan: 25-30 years
IUCN Red List Status: Vulnerable
Population: 20-30,000
Habitat: Forest, Shrubland, Grassland, Marine Oceanic, Marine Intertidal, Marine Coastal/Supratidal, Other
Distribution: Anywhere within or near the Arctic Circle, including Spitsbergen and Canada
Habitat
Polar bears inhabit areas of sea ice in the Arctic Circle, particularly enclosed areas of water known as ‘polynyas’ and temporary stretches of open water known as ‘leads’.
This area is known as the ‘Arctic ring of life’, and it’s favoured by the polar bear as there are more seals for them to hunt than in the high Arctic (towards the North Pole).
Their bodies are adapted to the cold conditions in that their feet are wide enough (up to 30cm in diameter) to avoid sinking into the snow and help them to swim, and they have also thick, shaggy, fur coats.
Polar bears are as comfortable in the water as on land, and they have been reported to be able to swim distances of up to 354 kilometres (220 mi) for up to 10 days!
One thing to bear in mind is that polar bears don’t hibernate like other bears. Pregnant females ‘den’, but that’s slightly different as I’ll explain later.
Hunting
Polar bears are carnivores and scavengers, and they eat a wide variety of marine animals:
ringed seal (Pusa hispida)
bearded seal (Erignathus barbatus)
harp seal (Pagophilus groenlandicus)
harbour seal (Phoca vitulina)
hooded seal (Cystophora cristata)
walrus (Odobenus rosmarus)
beluga whale (Delphinapterus leucas)
narwhal (Monodon monoceros)
Arctic char/charr (Salvelinus alpinus)
fourhorn sculpin (Myoxocephalus quadricornis)
The majority of their diet consists of ringed and bearded seals, and they will rarely attack species such as the walrus as a full-grown male might be twice the size of a bear!
Mature animals will tend to eat the calorie-rich skin and blubber of the seal while younger bears focus on the protein-rich red meat.
Polar bears use a variety of hunting methods:
Still-hunting. This is when the bear sniffs out a seal breathing hole and then waits next to it until a seal arrives. Once it smells its breath, the bear will reach in with a forepaw and try to drag it out, then crush it by biting through its skull.
Stalking on ice. If a seal is resting on an ice floe, the polar bear will approach to around 100 yards and crouch to see if it’s been spotted. If not, it will carefully approach to around 10 yards before rushing to attack the seal. [There was a great example of a polar bear creeping up behind a seal on a David Attenborough show once, but the director censored the attack itself! Shame…]
Birth lair raid. Female seals create ‘lairs’ in the snow in which to give birth, so this is an obvious target for polar bears if they can find them.
Fishing. Polar bears don’t try to catch seals while underwater, but occasionally they will ‘fish’ for species such as the Arctic char.
Scavenging. Polar bears will often scavenge for food, and this is particularly true of subadults that either can’t defend a kill from a dominant male or visit the carcase of a seal after another bear has finished with it. This habit becomes a problem in inhabited areas as polar bears end up eating anything they can find, including potentially hazardous household and industrial waste.
Breeding
Females start mating at four or five years old while males take longer to mature and usually start at five or six, becoming more and more active until the age of 10.
Polar bears generally adopt a polygynous mating system, which means males mate with several females whereas females only mate with one male, but this is not always the case as has been shown by genetic testing of mothers and their cubs.
The mating season takes place in April and June each year.
Males may pursue a breeding female for up to 100 km (60 mi), and males will often fight for mating rights, resulting in scars and broken teeth.
After mating, a male will spend a few days with the female before taking off on his own.
Meanwhile, the fertilised egg goes through a process called ‘delayed implantation’, which means it only implants in August or September if - and it’s a big if! - the mother has put on enough fat to survive the long denning season.
In preparation for that, the mother has to build a ‘maternity den’ on land or on the sea ice (usually in snow but sometimes in the permafrost underground).
This has a narrow entrance tunnel leading to one, two or three chambers.
Polar bears typically den in the same place each year, and they spend the winter months there before ‘waking up’ from mid-February to mid-April.
This period of dormancy is not quite the same as hibernation: the bear’s heart rate does slow down from 46 bpm to 27 bpm, but it isn’t constantly asleep, and its body temperature doesn’t fall as it does for mammals that actually do hibernate.
Polar bear cubs will be born at some point between November and February.
A litter usually consists of two cubs, which will be blind, covered with light down and weigh less than 0.9 kg (2.0 lb).
Their mother will nurse them on fat-rich milk until they emerge on to the ice again in spring.
At that point, the mother will graze on local vegetation, and her cubs will play around the den for a couple of weeks.
Finally, the family will make the long walk back to the sea ice so that the female can start hunting for food again.
Like brown bear cubs, polar bear cubs imitate their mothers in learning how to hunt, fish and fight, and this is reflected in their play.
The cubs are obviously vulnerable when they’re very young, and they are sometimes killed and eaten by other polar bears. In fact, only 42% of them survived their first 12 months in a study carried out in Alaska in 2006 (down from 65% in 1991).
The mother will eventually wean her cubs when they are 1.5-2.5 years old, at which point she will either chase them away or abandon them.
The cubs then have to fend for themselves, which they usually do alone.
Territory
Brown bears have large home ranges and are not usually territorial except when fighting over resources.
Males generally cover more ground in order to gain access to food and females, while females stick closer to home, partly in order to protect their cubs and avoid meeting dangerous male bears.
Territories also vary across the world:
Coastal Alaska: home ranges for females are up to 24 km2 (9.3 sq mi) and for males are up to 89 km2 (34 sq mi).
British Columbia: bears of the two sexes travel relatively compact home ranges of 115 km2 (44 sq mi) and 318 km2 (123 sq mi).
Yellowstone National Park: home ranges for females are up to 281 km2 (108 sq mi) and up to 874 km2 (337 sq mi) for males.
Romania: the largest home range was recorded for adult males (3,143 km2, 1214 sq mi).
Central Arctic of Canada: where food sources are quite sparse, home ranges range up to 2,434 km2 (940 sq mi) in females and 8,171 km2 (3,155 sq mi) in males
Communication
Polar bears communicate using a variety of noises:
moans (between mothers and cubs)
huffs (sign of nervousness)
chuffs (between mothers and cubs or a sign of nervousness)
snorts (sign of nervousness)
bleats (the distress calls of both cubs and subadults)
hisses (sign of aggression)
growls (sign of aggression)
roars (sign of aggression)
hums (cubs while suckling)
Threats
There have been many attempts to make the polar bear into the poster child for climate change, and it’s true that any reduction in sea ice in the Arctic would severely impact its ability to hunt for seals, and global warming might affect mothers’ ability to build dens.
However, recent studies suggest that polar bear numbers are rising, and the current world polar bear population may be as high as 31,000.
The IUCN deems the brown bear to be in its ‘Vulnerable’ category, but it refuses to say what the population is or whether it’s going up or down…!
In fact, polar bear mortality is poorly understood as carcases are rarely found, so it’s hard to know what threats they face apart from starvation and predation (by brown bears or other polar bears).
The good news is that the death of the polar bear has been greatly exaggerated, so let’s enjoy them while we can.
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