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Image: © Tom/Stock.adobe.com
The Inuit people prepare clothes using polar bear fur with its sebum coating intact, protecting them from the cold.
An international team of scientists have found that sebum, or the grease that coats hair, is what allows polar bears to stay insulated and thrive in some of Earth’s most punishing climates.
The scientists, from across European universities and organisations, collected hair from six polar bears in the wild, and they found that sebum, which is made up of cholesterol, diacylglycerols and fatty acids, is what makes it very hard for ice to attach to the bears’ fur.
The results of this study sheds new light on not just polar bears, but also Inuit ecology, the researchers say, while also allowing for newer innovations in the development of anti-ice surface coating and ski skins used by skiers and snowboarders.
Explaining their methodology, Julian Carolan, a PhD student from Trinity College Dublin’s School of Chemistry and the Amber Research Ireland Centre, said: “We measured ice adhesion strength, which is a useful measure of how well ice sticks to fur; hydrophobicity, which dictates whether water can be shed before it freezes; and freezing delay time, which simply shows how long it takes for a drop of water to freeze at certain temperatures on a given surface. We then compared the performance of the polar bear hair with that of human hair and two types of specialist human-made ‘ski skins’.
“The sebum quickly jumped out as being the key component giving this anti-icing effect as we discovered the adhesion strength was greatly impacted when the hair was washed. Unwashed, greasy hair made it much harder for ice to stick,” added Carolan, who is also the first author of the research, which was published in the journal Science Advances.
“In contrast, when the polar bear hair was washed and the grease largely removed, it performed similarly to human hair, to which ice sticks easily whether it is washed or greasy.”

A polar bear’s insulating fur shown under infrared heat imaging taken with a FLIR E75 24o (FLIR Systems OÜ, Estonia) Svalbard Archipelago, Norway. Image: © Jon Aars, Norsk Polarinstitutt
Moreover, the team’s research found that, unlike human hair, polar bear hair does not contain squalene, a metabolite, which is also present in aquatic animals such as sea otters, suggesting that its absence in the bears is very important from an anti-freezing perspective.
“Animals living in polar habitats have emerged as a source of inspiration for the development of new anti-icing materials,” said Dr Richard Hobbs, a Royal Society-Science Foundation Ireland University Research Fellow and an assistant professor in Trinity’s School of Chemistry and the Amber centre.
“Our work shows that polar bear fur provides an alternative strategy to produce an anti-icing surface based on the characteristic blend of lipids present in their fur sebum or hair grease.
“This work not only represents the first study of the composition of polar bear fur sebum, but it also resolves the question of why polar bears don’t suffer from ice accumulation. Despite having thick layers of insulating blubber and fur, and spending extensive periods in water at sub-zero temperatures, it seems that the fur grease provides a natural route for polar bears to easily shed ice when it forms due to the low ice adhesion on their fur,” he added.
Hobbs, who is also a senior author of the journal article, said that this research will help develop new, more sustainable anti-icing coatings, which may help replace products with ‘forever chemicals’ such as PFAS, which are harmful to the environment.
Aside from helping scientists better understand how polar bears withstand freezing temperatures, this discovery also lends to a better understanding of hunting behaviours – of both bears and the Inuit populace.
“One of the polar bears’ main hunting strategies is ‘still hunting’, where they lay motionless beside a breathing hole on sea ice waiting for seals to surface,” explained Prof Bodil Holst from the University of Bergen, and a senior author of the journal article.
“Still hunting frequently develops into an ‘aquatic stalk’ with the polar bear using its hind paws to slide into the water to pursue its prey, and the lower the ice adhesion, the less noise generated and the faster and quieter the slide.
“Our findings also help us understand the subtlety of the steps taken by Inuit people to optimise hunting strategies to mimic the polar bear method of still hunting. Inuit hunting stools are sometimes shod with polar bear fur on the feet to avoid noise when moving on the ice, while people also sometimes wear ‘polar bear trousers’, ensuring the entire contact area with the ice is covered in low ice-adhesion polar bear fur for optimal noise reduction.”
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