How polar bear fur stays ice-free
A brilliant idea led nanophysicist Bodil Holst to investigate why polar bear fur doesn't freeze. Now, her research on the deicing properties of polar bear fur has been published as the cover story in Science Advances.
By: Håvard Kroken Holme and Åshild Nylund
Published: (Updated: )
Bodil Holst is a professor of nanophysics at the Department of Physics and Technology at the University of Bergen (UiB). The groundbreaking study, published in Science Advances (external link), is the first to investigate why polar bear fur doesn't freeze.
Professor Holst got the idea for the project from the German TV show «Wer weiß denn sowas?» which showed that polar bears are invisible to infrared cameras, indicating that their fur has the same temperature as their surroundings. This piqued her curiosity, especially since she was already researching deicing properties of materials.
"I was so fascinated and thought: 'How is this possible? How can they jump into the water, be so well insulated, and not get covered in ice?'"
She then contacted colleagues at the Norwegian Polar Institute (external link) in Tromsø and obtained polar bear fur to investigate how ice interacts with the fur. Ph.D. student Julian Carolan (external link) from Trinity College Dublin (external link) conducted experiments showing that polar bear fur has anti-icing properties comparable to the best fluorinated ski skins. As a physicist, Holst initially hoped that the structure of the polar bear hairs was led to these properties, but realized quite quickly that it’s the hair grease.
News around the world
The story about the polar bear fur's properties have been shared in media and social media around the world.
CNN have posted a video about it on Tiktok and on their website, with an interview with Ph.D. student Julian Carolan:
Watch CNN's video with the interview here (external link).
From polar bear fur to eco-friendly ski skins
To understand why the fat has these properties, Holst collaborated with Professor Øyvind Halskau's group at the Department of Biological Sciences (BIO) at UiB and quantum chemists from the University of Surrey (external link). They identified specific compounds in the fat that are key to its anti-icing properties. The researchers found that polar bear fur is highly effective at preventing ice buildup, similar to materials coated with special chemicals like fluorocarbons. This is due to the sebum (hair grease) that covers the fur. By analyzing the fats in the fur, they discovered that it contains cholesterol, diacylglycerols, and special fatty acids. Surprisingly, it does not contain squalene – an organic compound with the chemical formula C₃₀H₅₀, often used as a natural moisturizer in cosmetics. Calculations show that the identified fats have a low propensity to accumulate ice, while squalene is very prone to attracting ice. This suggests that the composition of the hair grease prevents polar bear fur from freezing.
The research has led to a patent application to develop an eco-friendly ski wax based on these compounds, which can be synthetically produced. Holst also collaborated with ski manufacturer Åsnes, who provided ski skins for comparison in the experiments. This collaboration has been crucial in understanding the practical applications of the findings.
"The aim is to one day have a new polar bear-inspired ski wax, which is environmentally friendly," she says.
Inuits knew the secrets of polar bear fur long before modern science
During a visit to the National Museum of Denmark (external link), Holst observed how the Inuit have used polar bear fur for centuries. She noticed how the Inuit shut the legs of the hunting stool, and even put polar bear fur slippers under their boots, to prevent it from freezing to the ice and to reduce noise.
"This shows that the Inuit have known about the unique properties of polar bear fur long before modern science," Holst says enthusiastically.
"Our research has enhanced understanding of how polar bears adapt to their environment. They must be very quiet when hunting because seals have excellent hearing. Over the past decade, behavioral biologists have noted that polar bears mostly hunt by lying still near breathing holes, striking quick and silent as seals appear. The low friction from the fat on their fur makes this possible, much like oil removes squeaks from a door," concludes Bodil Holst.
Read more:
- Polar bear fur has a built-in deicing feature - Science.org (external link)
- Polar bear fur could hold the secret to replacing 'forever chemicals' - Washington Post (external link)
The Cover of Science Advances, volume 11, issue 5, 2025.