Tiergarten Nürnberg

Systematology

Scientific name

Descent

Characteristics

• comparatively slim body with long neck
• narrow head with small eyes and outer ears
• paddle-like paws with webbed toes
• short tail (7 to 13 centimetres)
• five short, non-retractable claws
• body covered with hair, with the exception of the lips, the nose and part of the soles of the feet
• underwool up to 5 centimetres, guard hair/ top hair at the belly up to 15 centimetres
• heat-insulating layer of fat under the skin (up to 10 centimetres)
• hairs hollow, almost transparent and light-conducting
• 42 teeth

Colour

• fur white to yellowish white
• skin, lips, nose and claws black
• tongue blue

Measurements

• largest living predator on land
• male: 2.0 to 2.6 metres, rarely over 3 metres in length, shoulder height up to 1.6 metres
• female: 1.8 to 2.1 metres in length, shoulder height up to 1.4 metres

Weight

• adult male: 300 to 800 kilograms, according to historic reports up to 1 ton
• adult female: 150 to 350 kilograms, pregnant female over 500 kilograms

Distribution

• across the entire North Pole area, mainly north of the Polar Circle
• Alaska, Canada, Greenland, Spitzbergen and Siberia
• Individual animals observed between 46 and 88 degrees north

Habitat

• North Pole Sea (pack ice, ice fields)
• islands and coastal strips (tundra)

Roaming area

• Polar bears can cover distances of many thousand kilometres each year.
• Every year, they roam 10,000 to 600,000 square kilometres.

Sense Organs

• Their sense of smell is excellent. Polar bears can sniff the snow-covered breathing hole of a seal from a distance of one kilometre. They can probably smell cadavers from a distance of 30 kilometres.
• Their hearing is a bit better than that of humans.
• Their sight is comparable with that of humans.

Movement

• Polar bears walk on the soles of their feet.
• Walking/Running: up to 70 km per day, short sprints at over 40 km/h
• Jumping: on land up to 4 metres and 2.3 metres out of the water
• Climbing: for example on steep slopes of up to 45 degrees incline
• Swimming: speeds up to 9.6 km/h and distances of 65 kilometres without rest
• Diving: in shallow waters, up to 2 minutes

Food

• mainly ringed seals, more rarely bearded seals, harp seals and hooded seals
• cadavers of walruses and whales
• occasionally small mammals, birds, fish, herbs, berries, seaweed
• cannibalism (rare): mainly adult males eating cubs
• polar bears can fast for up to 12 months

Hunting behaviour

• pack ice or drift ice is essential for hunting success
• creeping up on seals' birth lairs and breathing holes
• diving underwater to seals' resting places on ice floes
• lying in wait in front of breathing holes or places where seals go to sunbathe
• diving underwater then jumping to catch sea birds (rare)
• attacking walruses and small whales (rare)
• hunting reindeer on land (rare)

Social Structure

• solitary
• cubs stay with the mother for up to 2.5 years

Sexual Maturity

• male: mature at 5 to 6 years, in the wild able to compete with other males at 8 to 10 years
• female: mature at 4 to 5 years

Reproduction

• mating season between April and June, depending on region
• usually, several males compete for one female ready to conceive

Length of Pregnancy

Size of Litter

• twins (70 per cent)
• one cub (25 to 30 per cent)
• very rarely triplets or quadruplets

Interval Between Litters

• at least 3 years (if previous cubs were reared successfully)
• 1 year (if previous cubs were lost)

Birth Weight

Birth Den

• pregnant females dig a snow den in late autumn
• the birth den usually consists of a tunnel (1 to 3 metres' length, rarely up to 6 metres) and basin (about 2 to 3 square metres)
• usually on land, near the coast (in so-called "denning areas")
• in some regions also on perennial pack ice (drift ice)

Development of Cubs

• the cubs are helpless, blind and deaf when born, with very thin fur
• rapid development with polar bear milk (about 30 per cent fat content at first)
• open their eyes at the end of the first month
• during the second month, first teeth break through
• in the second month, the cubs can hear
• in the third month they stand securely on all fours
• at 3 to 5 months, they leave the birth den
• after leaving the birth den, they take solid foods for the first time
• in the fourth month, the milk teeth are complete
• at about 8 to 10 months, the cubs can hunt their first prey
• weaning at 2 to 2.5 years (rarely earlier, e.g. at 1.3 years)
• the cubs leave the mother after weaning

Life Expectancy

• 20 to 35 years in the wild
• in zoos, polar bears have lived up to 43 years

Stock

• 20,000 to 25,000 animals in about 20 populations
• status "vulnerable" on the IUCN Red List

Natural Enemies

• none, apart from man
• young and weak animals are sometimes threatened by other polar bears and wolves

Threats

• global warming (pack ice melting, less hunting time)
• pollution of oceans (poisonous chemicals, crude oil)
• over-fishing (less food for the seals)
• disturbances due to mining of raw materials, military use, shipping, tourism
• commercial hunts (in some populations)
• illegal trading of polar bear products (e.g. gall bladders)

Protection

• International Agreement on Protection of Polar Bears (1976)
• regional hunting bans