GOING FOR A SWIM: Polar bears spend a lot of time in water, hunting fish, seals, and whales.

OLE JORGEN LIODDEN/NPL/MINDEN PICTURES; SHUTTERSTOCK.COM (BACKGROUND)

STANDARDS

NGSS: Core Idea: LS1.A, PS1.A

CCSS: RI.2

TEKS: 6.2D, 7.2D, 8.2D, CHEM.2D, CHEM.7C

Investigate It!

The Slippery Secrets of Polar Bear Fur

Researchers figure out how polar bears avoid getting covered in ice—despite living in the freezing Arctic.

January 19, 2026

By Jennifer Barone

AS YOU READ, THINK ABOUT the functions of hair and fur in various animals.

A few years ago, physicist Bodil Holst of the University of Bergen in Norway was watching a quiz show on TV. Someone on the show mentioned that polar bears are difficult to see with heat-detecting cameras. Thick layers of fat and fur insulate the bears so well that very little heat escapes from their body. In fact, polar bear fur is roughly the same temperature as the animals’ bitter-cold surroundings.

A few years ago, Bodil Holst was watching a quiz show on TV. Holst is a physicist at the University of Bergen in Norway. Someone on the show mentioned a fact about polar bears. They’re difficult to see with heat-detecting cameras. Thick layers of fat and fur insulate the bears, so very little heat escapes from their body. In fact, polar bears’ fur and their bitter-cold surroundings are about the same temperature.

PICTURE BY TAMBAKO THE JAGUAR/GETTY IMAGES

SHAKE IT OFF! After coming out of the water, the bears shake their fur to help dry it.

That little piece of nature trivia got Holst thinking. She knew polar bears hunt in the ocean. That means their fur is wet every time they get out of the water. If their dripping fur gets as cold as the frigid air around it, she wondered, why don’t the bears end up covered in ice?

Holst, who usually studies the structure of surfaces, never expected to investigate one of the most iconic animals on the planet. But the question kept nagging at her. Holst teamed up with scientists from many specialties to explore the secrets of polar bear fur. They discovered that these animals have a natural solution for keeping ice away—one that rivals the best anti-icing materials invented by people.

That little detail made Holst wonder. Polar bears hunt in the ocean. When they get out of the water, their fur is wet. And their dripping fur gets as cold as the frigid air around it. So why don’t they end up covered in ice?

Holst usually studies the structure of surfaces. She never expected to study one of the most famous animals on the planet. But the question kept nagging at her. So Holst set out to explore the secrets of polar bear fur. She teamed up with scientists from many specialties. They discovered that these bears have a natural way to keep ice away. And it rivals the best anti-icing materials invented by people.

SPECIAL FUR

Some of Holst’s collaborators who study polar bears shared their observations about the animals’ fur. These notes hinted that the fur had some exceptional slipperiness that might help it stay ice-free.

One clue came from the Norwegian Polar Institute, which monitors and studies polar bears. Researchers with the Institute occasionally track polar bears with helicopters. They use tranquilizer darts to put the bears to sleep briefly so the scientists can safely collect data and samples to check the animals’ health. These colleagues shared that polar bears sometimes tried to get away from the helicopters by sliding down slopes instead of running.

Another hint came from a conservator at the National Museum of Denmark. She described a hunting stool in the museum’s collection that had been crafted by the Inughuit—Indigenous people of Greenland. The stool had polar bear fur on its feet, which allowed hunters to slide it silently across snow and ice. Inughuit hunters sometimes strapped polar bear fur to the soles of their boots for the same purpose.

Some of Holst’s colleagues study polar bears. They shared their observations about the animals’ fur. These notes hinted that the fur was very slippery. That might help it stay ice-free.

One clue came from the Norwegian Polar Institute. Scientists there monitor and study polar bears. Sometimes, they track polar bears with helicopters. They use tranquilizer darts to put the bears to sleep briefly. Then scientists can safely collect data and samples to check the animals’ health. These colleagues shared how polar bears tried to get away from the helicopters. Instead of running, they sometimes slid down slopes.

Another hint came from a conservator at the National Museum of Denmark. She described a hunting stool in the museum’s collection. The Inughuit had crafted it. They’re Indigenous people of Greenland. The stool had polar bear fur on its feet, so hunters could slide it silently across snow and ice. Inughuit hunters sometimes strapped polar bear fur to the soles of their boots. It served the same purpose.

PUTTING IT TO THE TEST

Intrigued, Holst decided to conduct experiments to learn more about the properties of polar bear fur. The Polar Institute provided samples of fur for analysis. Holst and co-investigator Julian Carolan, a materials scientist at Trinity College in Ireland, examined the fur under a microscope. They looked at human hair as well. “We thought about photos of polar explorers whose beards were full of ice,” says Holst. “We suspected human hair would be an interesting comparison and probably not as good at anti-icing.”

The structure of polar bear fur looked similar to human hair, just with wider strands. But “it was obvious that the fur was covered in grease, and the samples smelled quite strongly,” says Holst. The oily substance was sebum, which protects and lubricates the skin of many mammals, including humans. The scientists wondered if it was the key to the fur’s slipperiness.

Next, Holst and Carolan tested the adhesion, or attachment strength, of ice to the fur—and to greasy human hair. “I let my hair get greasy by going just over a week without washing and then shaving it off,” says Carolan. “The process was a little gross,” he adds, so it was a relief to finally shave. The researchers froze blocks of ice onto the samples of Carolan’s greasy hair and polar bear fur. They then used a device to measure the amount of force needed to push the ice blocks off the samples.

The researchers repeated the experiment with washed samples of fur and human hair to see if removing sebum affected adhesion. They also did the same test with ski skins. Backcountry skiers attach these pads to skis when climbing hills. The pads provide grip to prevent skiers from slipping back down a hill—but they must glide smoothly when skiers are moving forward uphill. The skins are made of goat hair sprayed with synthetic, or lab-made, coatings to enhance glide. These nonstick coatings often contain PFAS, chemicals that are harmful to both human health and the environment (see “You Can’t Escape These Chemicals!,” Science World, March 13, 2023).

The results of the experiments showed that unwashed polar bear fur releases ice far more easily than greasy human hair, washed human hair, and washed fur. It’s also about as slippery as the top-performing ski skin coated with PFAS (see “Freeze Test”). Carolan was excited about the results—even if he was “maybe a little disappointed” to learn that his own hair had no anti-icing properties.

Holst wanted to learn more about the properties of polar bear fur. So she decided to conduct experiments. The Polar Institute provided samples of fur to test. Holst worked with Julian Carolan, a materials scientist at Trinity College in Ireland. They examined the fur under a microscope. They also looked at human hair. “We thought about photos of polar explorers whose beards were full of ice,” says Holst. “We suspected human hair would be an interesting comparison and probably not as good at anti-icing.”

The polar bear fur looked similar to human hair. It just had wider strands. But “it was obvious that the fur was covered in grease, and the samples smelled quite strongly,” says Holst. The oily substance was sebum. It protects and lubricates the skin of many mammals, including humans. Was it the key to the fur’s slipperiness?

Next, Holst and Carolan looked at adhesion, or attachment strength. They tested the adhesion of ice to the fur and to greasy human hair. “I let my hair get greasy by going just over a week without washing and then shaving it off,” says Carolan. “The process was a little gross,” he adds. He was relieved to finally shave. The researchers froze blocks of ice onto the samples of Carolan’s greasy hair. They also froze some onto polar bear fur. Then they pushed the ice blocks off the samples. A device measured how much force this took.

The researchers washed some samples of fur and human hair to remove sebum. Then they repeated the experiment with them. They also did the same test with ski skins. Backcountry skiers attach these pads to skis when they climb hills. The pads provide grip so skiers don’t slip back down a hill. But they must glide smoothly when skiers move forward uphill. The skins are made of goat hair. To improve glide, the hair is sprayed with synthetic, or lab-made, coatings. These nonstick coatings often contain chemicals called PFAS. They’re harmful to both human health and the environment (see “You Can’t Escape These Chemicals!,” Science World, March 13, 2023).

The experiments showed that unwashed polar bear fur is very slippery. It releases ice far more easily than greasy human hair, washed human hair, and washed fur. It’s about as slippery as the best PFAS-coated ski skin (see “Freeze Test”). Carolan was excited about the results. But he was “maybe a little disappointed” that his own hair had no anti-icing properties.

FREEZE TEST

SCIENCE.ORG/DOI/10.1126/SCIADV.ADS7321

PUSH! The scientists measured the force required to remove ice frozen to the fur.

The bar graph below shows how strongly ice stuck to different samples tested by Holst and Carolan. Higher adhesion means ice is harder to remove, while lower adhesion means ice comes off more easily. How does the adhesion strength of ice on washed polar bear fur compare with that of unwashed fur? What about washed versus unwashed human hair?

FREEZE TEST

SCIENCE.ORG/DOI/10.1126/SCIADV.ADS7321

PUSH! The scientists measured the force required to remove ice frozen to the fur.

GREAT GREASE

The ice investigation suggests that polar bear sebum gives the fur its anti-icing abilities. That relates to an odd behavior scientists have observed in the wild: After coming out of water, polar bears first shake their fur like a dog to remove most of the water. Then they often roll in snow. The rolling may freeze any remaining water into ice, which easily slips off the greasy fur.

The ice study suggests that polar bear sebum is the key. It gives the fur its anti-icing abilities. That relates to an odd polar bear behavior in the wild. Scientists have observed the animals coming out of water. First, the bears shake their fur like a dog. This removes most of the water. Then they often roll in snow. That may freeze any remaining water into ice. The ice easily slips off the greasy fur.

Chemists partnering with Holst analyzed polar bear sebum. They found that it contains a mixture of oily compounds, including fatty acids and cholesterol—but it’s missing one called squalene. This natural oil is found in many mammals’ sebum and adheres strongly to ice. Further analysis of polar bear sebum could guide scientists toward synthetic coatings that are safer than PFAS and completely biodegradable, or able to break down naturally in the environment. Such substances could be used in ski skin coatings, lubricants, waxes, outdoor clothing and sporting gear, and even in fluids used to remove ice from aircraft.

Holst is grateful to have had the chance to follow her curiosity and explore research outside her normal area of study. According to Carolan, the polar bear project highlights “the value of looking to nature for inspiration.”

Chemists worked with Holst, and they examined polar bear sebum. They found that it contains a mixture of oily compounds, including fatty acids and cholesterol. But it’s missing one called squalene. This natural oil is found in many mammals’ sebum. It sticks strongly to ice. Further study of polar bear sebum could lead to new synthetic coatings. Scientists may develop ones that are safer than PFAS and completely biodegradable. They would break down naturally in the environment. These substances could be used in ski skin coatings, lubricants, waxes, outdoor clothing, and sporting gear. They could even be used in fluids that remove ice from aircraft.

Holst is glad she followed her curiosity. She’s grateful she got to explore research outside her normal area of study. And Carolan says that the polar bear project highlights “the value of looking to nature for inspiration.”