It's National Polar Bear Day!
This is a great day to learn about the mighty mammals and appreciate that they're a valuable animal but are worryingly endangered.

Scientists have studied the evolution of polar bears and concluded that they developed from the traditional brown bear around 6 million years ago.

Polar bears are the world's largest carnivore.

Fully grown polar bears can be as tall as 9 feet (2.7 metres).

Polar bears live in countries that ring the Arctic Circle such as Canada, Russia, the United States (in Alaska), Greenland and Norway.  In the winter, temperatures in the Arctic are usually around - 29 degrees Fahrenheit (- 34 degrees Celsius) and can reach as low as - 92 F (- 69 C).

Polar bears have small, round ears and their tails are short. This helps them conserve heat.

Polar bears are really good at swimming; their scientific name is Ursus Maritimus which means "sea bear". 

These bears have been known to swim more than 60 miles at a time. 

Baby polar bears are called cubs.

A cub only weighs 1.3 pounds (about half a kilogram) - about the weight of a guinea pig!

Female polar bears who are pregnant will dig a snow den before giving birth. They then come out from the den three months later. They usually give birth during November or December and have one, two or three cubs.

To build a snow den, they start to dig a small cave, they then wait for the snow to fall and block the entrance.  

During winter polar bears will also sleep in shallow dens that they have dug in the snow. The snow in their den will pile on top of them and provide warmth just like a blanket! They can sleep through winds and storms and sometimes they will stay curled up in their den for several days until the weather gets better.

In the wild polar bears can live up to 30 years.

Most polar bears sleep for seven to eight hours - just like humans!

Polar bears have built-in socks. The bottoms of their paws are covered with fur to keep them warm and to help grip surfaces when it's slippery.

They have an excellent sense of smell and can sniff out prey from up to 16km away (over 50,000 feet!).

Polar bears often get hot and will roll in the snow to cool off. 

Underneath the fur, a polar bear's skin is actually black. This black skin soaks up the sun's heat and helps them stay warm.

Polar bears have 42 teeth, their cheek teeth are sharp so they can get chunks of meat. Their canine teeth are long and sharp which helps with catching prey.

The polar bear was the mascot for the 1998 Winter Olympics in Canada.

The Russian name for polar bear is "beliy medved", meaning the white bear. In Norway and Denmark, the polar bear is called "isbjorn", which means the ice bear.