© Craig Taylor/Polar Bears International
11/6/2018 9:54:51 PM
Our 10 Favorite Facts About Polar Bears
By Alysa McCall, Director of Conservation Outreach and Staff Scientist
As we celebrate the bears during Polar Bear Week, we wanted to share 10 of our favorite polar bear facts:
- Polar bears are the largest four-legged predator. Adult males normally weight 350 to more than 600 kilograms (775 to more than 1,300 pounds). Adult females are smaller, normally weighing 150 to 290 kilograms (330 to 650 pounds).
- Polar bears are one of the most mobile four-legged animals, if not the most. Polar bears can travel more than 3000 kilometers per month and can have home ranges that exceed 600,000 square kilometers (an area larger than California or the entire Yukon in one year!).
- Polar bears can fast (i.e., not eat) for up to eight months. After feeding throughout the winter, a pregnant female polar bear builds a maternity den in the fall where she will give birth to her cubs and nurse them. She’ll emerge with her cubs in the spring and head to the sea ice to find seals—which means up to eight months with no meals for mom, an amazing feat.
- Polar bears weigh 1-1.5 pounds when born but grow more than 20 times their body weight in just a few months. When a family finally heads toward the sea ice in the early spring, cubs can already be 15-30 pounds at just two to three months old. Polar bear milk is the fattiest found on land, at about 31 percent fat when the cubs are born. This provides enough calories to help cubs grow rapidly.
- Polar bears have massive, sticky, furry feet. Polar bear paws measure up to 30 centimeters (11.81 inches) across. Tufts of fur between their toes and footpads help with warmth. 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.
- Polar bears navigate with their noses. A polar bear can likely smell a seal from more than 1 kilometer (0.6 miles) away and up to 1 meter (3 feet) under snow. Polar bears move cross-wind to encounter as many new scents as possible, turning upwind when something piques their interest. Females who are ready to mate release a pheromone scent through their paws. Male polar bears smell the footprints and follow females on the sea ice.
- Polar bears are incredible swimmers. The longest swim recorded was by a nine-year-old female who swam for 232 hours straight, covering 687 kilometers (427 miles). By the end, she had lost 22 percent of her body mass, and her yearling cub had died. While polar bears are great swimmers, they cannot outswim a seal. That’s why sea ice is so important to them—it gives them a platform from which to hunt their seal prey.
- Polar bears spar, or play fight, with each other. In the spring males fight hard for females, injuring each other in the process. In the fall there is no competition over mates or food so near Churchill, Manitoba males seem to become more social and engage in what we call “sparring” or play fighting. Sparring may help males test their strength and gauge how well they stack up to each other in preparation for the true fighting that will occur in the spring. You can see the big males wrestle throughout the day, check out the Polar Bear Cams to watch for yourself!
- Polar bears are the most carnivorous bear. We sometimes call them “lipovores” because their main source of calories comes from marine fat, or blubber. Polar bears assimilate the majority of the fat they eat directly into their own body fat. They can eat over 100 pounds of blubber in one sitting. Polar bears do not digest carbohydrates or proteins as well as brown bears do. They rely on seal prey reached via sea ice for the majority of their calories. The fat from seals will keep them going for much of the year and through times of extended fasting.
- Polar bears are at the top of the Arctic food chain but rely on the entire food web to stay alive. Eighty-six percent of the carbon that makes up the polar bear’s body is derived from the marine algae that grows within sea ice. Microorganisms like copepods eat the algae, fish each the copepods, seals eat the fish, and polar bears eat the seals. Just as soil and plants form the base of a forest or meadow food chain, sea ice and algae form the base of the sea ice food chain, supporting polar bears at the top.
Thank you for helping us take action on climate change this Polar Bear Week. With your support we can conserve polar bears and their sea ice home and also maintain a healthy planet for all of us!