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Everything you need to know about polar bears

The rulers of the Arctic, from rearing cubs to dealing with climate change
By Dr. Thea Bechshoft from Polar Bears International

What Is It?

White carnivorous bear that roams the Arctic Circle’s ice and snow.

Size

Polar bears are the largest four-legged predator. Adult males normally weigh from 350 to more than 600 kilograms (775 to more than 1,300 pounds). Adult females are smaller, normally weighing 150 to 295 kilograms (330 to 650 pounds).

Scientists usually refer to how tall bears are by measuring them at the shoulder when on all fours. Those heights are typically 1-1.5 metres (3.3-5 feet) for adult polar bears. An adult male may reach over three metres (10 feet) when standing on its hind legs.

Age

In the wild, polar bears live 15 to 18 years on average, although researchers have handled a few bears that were in their early 30s. In captivity, some bears reach their mid-to-late 30s. Debby, a captive bear in Canada, lived to be 42.

Where Are They Found

Polar bears are found all around the circumpolar Arctic, in the five ‘polar bear range countries’: Canada, US, Russia, Svalbard (Norway), and Greenland. Canada’s home to the most polar bears, approximately two thirds of the global numbers.

Photo by Tim Auer

Habitat

A healthy Arctic sea ice habitat, especially over the shallow, most biologically productive continental shelf areas, is essential for polar bears to survive. They use the sea ice platform to hunt seals, to breed, to transport themselves, and sometimes even to den on.

Pregnant denning females also need undisturbed areas in the winter for giving birth and raising their young during their first vulnerable months.

Food

Ringed and bearded seals make up the majority of a polar bear’s diet. Seals have a thick layer of fat (blubber), which provide the bears with the massive amount of energy they need to be healthy. A lack of seals means skinnier bears, which produce fewer and smaller cubs.

A polar bear can eat 10-20 per cent of its own body weight in one go and needs to ingest the calories equivalent to an average of one adult ringed seal per 1-1.5 weeks in order to survive long-term.

Photo by Tim Auer

Reproduction

A female polar bear will typically only have about five litters over the course of her life, each consisting of an average of two cubs. For this to happen, she has to be in good body condition (fat). If she’s too skinny, her body is unlikely to send the right hormonal signals for the pregnancy to happen. In a process called delayed implantation, the egg, fertilized during mating in the Spring, only implants and starts developing once the female goes into her maternity den around October or November. As cubs are born around the beginning of the new year, the true gestation period for polar bears is therefore only three to four months.

Newborn polar bear cubs are 30-35 cm long and weigh little more than half a kilogram. They are blind, toothless, and covered with short, soft fur. The female also needs to be in good enough body condition after the birth of her cubs to be able to produce sufficient milk for them during the average 2.5 years they stay together as a family group. Add to this the fact that cub mortality can be very high (upwards of 50 per cent in some cases), and you see why polar bear population numbers can only ever grow very slowly.

Photo by Tim Auer

Behaviour
Polar bears are largely solitary creatures, who prefer to spend their time roaming the Arctic sea ice and hunting seals. In some areas, though, the melting summer sea ice forces bears onto land, where they fast for months, waiting for the sea ice to return.

Despite some months being leaner than others, the only polar bears that den are the pregnant females, who spend the winter with their new-born cubs. All other polar bears are outside on the ice, mostly hunting and sleeping, with the occasional social encounter when their meandering path crosses that of another bear.

7 Incredible Facts

Polar bears’ fur isn’t actually white. Their hair is actually without colour. Each hair shaft is pigment-free and transparent, with a hollow core that scatters and reflects visible light, much like what happens with ice and snow, which makes their hair appear white to the human eye.

Polar bears are technically marine mammals. Contrary to all other bear species, there is no terrestrial prey that will sustain a polar bear long-term, so they have no interest in being on land. Given a choice, they spend most to all of their lives on the frozen surface of the Arctic waters, where they hunt, travel, breed, and raise their young.

Polar bear paws measure up to 30 centimetres across, to help the bears tread on thin ice. Black footpads on the bottom of each paw are covered by small, soft bumps known as papillae. Papillae grip the ice and keep the bear from slipping. Tufts of fur between its toes and footpads can help with security as well.

The word ‘Arctic’ comes from the Greek word for ‘bear’, while ‘Antarctic’ comes from the Greek for ‘opposite of the Arctic’ or ‘opposite of the bear.’

Unlike other large carnivores, polar bears have home ranges, not territories. Polar bears can travel more than 3,000 kilometres per month and can have home ranges that exceed 600,000 square kilometre, an area larger than California or the entire Yukon, in one year. Unlike a territory, home ranges are not defended, so individual polar bear’s home ranges overlap with other bears.

Polar bears are incredible swimmers. The longest swim recorded was by a nine-year-old female who swam for 232 hours straight, covering 687 kilometres (427 miles). While polar bears are great swimmers, they cannot out-swim a seal. That’s why sea ice is so important to them. It gives them a platform to hunt their seal prey from.

Polar bears can fast (go without food) for up to eight months. After feeding throughout the winter, a pregnant female polar bear builds a maternity den in the autumn, where she can give birth and nurse her cubs. She’ll emerge with her infants in the Spring and head to the sea ice to find seals to hunt, which means the mother lasts up to eight months without food.

Photo by Simon Gee

How Many Polar Bears Are On The Planet Today?

Scientists estimate the global polar bear population is around 20,000 to 25000. The IUCN Polar Bear Specialist Group lists the polar bear as a vulnerable species, citing sea ice loss from climate change as the single biggest threat to their survival. Polar bears are dependent on sea ice, and all sea ice is being affected by the increasing temperatures in the Arctic.

However, sea ice has different movement patterns depending on the specific area of the Arctic. Researchers have divided the Arctic into four different regions, according to these patterns. The western Hudson Bay polar bear population experiences seasonal sea ice, in that the sea ice melts completely every summer and re-freezes each winter. During the increasingly longer ice-free period, the bears here have no choice but to fast on land. In the late 1980s and mid-1990s, this population was estimated at approximately 1200 bears. In 2016, however, this number was down to approximately 800 bears – around a 30 per cent decline over as many years.

Without action on climate change, we could see dramatic declines in polar bear numbers by the middle of this century.

Photo by Tim Auer

The Greatest Threats To Polar Bears….

Habitat Loss: The rapid loss of sea ice is the primary threat to polar bears’ long-term survival. Our reliance on fossil fuels and the resulting climate change is currently causing a 13 per cent decline per decade in the sea ice extent (September minimum). As polar bears are reliant on the sea ice as a seal hunting platform, this decline is profoundly affecting them in many areas already.

Pollution: Persistent pollutants, such as PCBs, pesticides, and heavy metals, are being transported to the Arctic with the wind and ocean currents, where they’re incorporated into the Arctic ecosystem and magnify up through the food chain. As the top predator of this ecosystem, polar bears ingest high amounts of these chemical compounds, something that leads to a myriad of detrimental health effects.

Disturbance: Climate change leads to a more accessible Arctic and to an increase in commercial activity and use of the region. This leads to an increase in conflicts between humans and polar bears, as well as to an increase in human disturbances in historically important polar bear denning areas.

What Can People Do To Help?

Combatting climate change is the most important factor in protecting polar bears and ensuring their existence for generations to come. There are several steps people can take to do this.

Vote and speak up: Vote with the climate in mind, in each and every election. Let your representatives know you support bold climate action and a swift transition to clean energy sources.

Support an energy shift: Support projects that reduce or replace fossil fuels with clean energy sources, such as solar and wind. Research renewable energy options available to you.

Talk about it: Open up and talk about climate change (and climate change solutions) with friends, family members, and colleagues. Share this article.

Promote clean transportation: Support projects that aim at reducing the number of vehicles overall, such as car-sharing programs and mass-transit programs. Build a better future: Encourage energy-efficient construction standards, including better heating and cooling systems, insulation, and lightning methods.


Dr. Thea Bechshoft is a staff scientist at Polar Bears International.

Polar Bears International: www.polarbearsinternational.org.

Follow Polar Bears International on Instagram: @polarbearsinternational.

Please SHARE this article.

NOTE: The best way to solve the crises facing the planet and its wildlife is by having open, honest, respectful conversations and hearing diverse voices from around the world. The New Big 5 project does not necessarily support or agree with every opinion or idea expressed by photographers, conservationists or organisations featured on the New Big 5 website. The many different wildlife charities, photographers, film-makers and conservationists we’ve collaborated with also do not necessarily support or agree with every idea or opinion expressed by other people or organisations on the website. It’s ok to disagree and debate. But we hope the opinions and ideas can inspire people, make people think, and be part of the conversation to help our planet and the animals that live on it.

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