Scientists have unveiled the anti-icing mystery behind polar bear fur, which enables these remarkable creatures to survive in some of the harshest environments on Earth. The key to their resilience? Oily hair. Through extensive research, analyzing fur collected from six wild polar bears, researchers pinpointed the crucial element — the hair’s “sebum” (or grease). This sebum consists of cholesterol, diacylglycerols, and fatty acids, effectively preventing ice from adhering to their fur.
An international team of scientists has uncovered the anti-icing secret of polar bear fur — a remarkable adaptation that allows these iconic animals to flourish in one of the planet’s most extreme environments. The magic ingredient? Greasy hair.
Through meticulous investigation, which included examining hair samples from six polar bears in their natural habitat, the researchers identified the hair’s “sebum” (or grease) as the vital protective element. This sebum, composed of cholesterol, diacylglycerols, and fatty acids, significantly inhibits ice from adhering to their fur.
This discovery not only enriches our understanding of polar bear and even Inuit ecology but could also lead to diverse applications, such as an artificially produced sebum that might serve as an effective anti-ice surface coating for various uses, including next-generation ski skins for winter sports enthusiasts.
Julian Carolan, a PhD Candidate at Trinity College Dublin’s School of Chemistry and the AMBER Research Ireland Centre, is the lead author of the study, which has been published today as the cover story in the esteemed journal Science Advances.
He noted: “We evaluated the strength of ice adhesion, which indicates how well ice sticks to fur; hydrophobicity, which determines the capacity to shed water before it freezes; and the delay time before freezing, showing how long it takes for a drop of water to freeze at specific temperatures on a given surface. We compared polar bear fur with human hair and two kinds of specialized human-made ski skins.”
“The sebum quickly stood out as the critical factor responsible for the anti-icing effect, as we found that washing the hair significantly altered its adhesion strength. The unwashed, oily hair made it far more difficult for ice to adhere. Conversely, when the polar bear hair was washed, eliminating most of the grease, its performance matched that of human hair, to which ice easily clings, regardless of its grease content.”
This discovery prompted the team to conduct an in-depth chemical analysis of polar bear sebum. In addition to identifying the main components (cholesterol, diacylglycerols, and fatty acids), they were surprised to find that “squalene” was missing. This fatty substance is typically found in human hair and other aquatic creatures like sea otters, suggesting that its absence in polar bear hair is crucial for their anti-icing ability.
Dr. Richard Hobbs, an Assistant Professor and Royal Society-Science Foundation Ireland University Research Fellow at Trinity’s School of Chemistry and the AMBER Research Ireland Centre, is a senior author of the study. He added: “Animals inhabiting polar regions have become a source of inspiration for creating new anti-icing materials.
“For instance, Anne Kietzig’s group at McGill recently discovered that the unique structure of Gentoo penguin feathers provides anti-icing properties that hinge on the feather architecture instead of the oil coating. Our research highlights that the lipid composition of polar bear fur sebum offers an alternative method for creating anti-icing surfaces.”
“This research not only represents the first investigation into the composition of polar bear fur sebum, but it also clarifies why polar bears do not experience ice build-up. Despite their thick layers of insulating fat and fur and spending long periods in icy waters, it appears that their fur grease allows them to easily shed ice because of the low adhesion of ice to their fur.”
“We believe that these natural lipid coats from bears can guide us in developing new, more sustainable anti-icing solutions that could replace problematic ‘forever chemicals’ such as PFAS that are currently used in anti-icing applications.”
Beyond structural insights, these intriguing discoveries also enhance our understanding of hunting behaviors in both polar bears and indigenous Inuit communities.
Prof. Bodil Holst from the University of Bergen is a senior author of the article. She remarked: “One of the polar bears’ primary hunting methods is ‘still hunting’, where they remain motionless near a breathing hole in the ice, waiting for seals to emerge. This method can lead to an ‘aquatic stalk’, where the polar bear uses its hind legs to glide into the water to chase its prey. With lower ice adhesion, less noise is made, allowing for stealthier movements.”
“Our findings also provide insight into the careful tactics used by Inuit people to enhance their hunting strategies, closely mimicking the polar bear’s still hunting approach. Inuit hunting stools are sometimes fitted with polar bear fur on the feet to minimize noise on the ice, and individuals occasionally wear ‘polar bear trousers’ to ensure the entire area in contact with the ice is covered in low-ice-adhesion polar bear fur to reduce sound.”
Notably, the traditional Inuit method of preparing the fur maintains the sebum by avoiding washing the hair side, which is different from other animal furs, like fox skins, which are typically cleaned with soapstone or dry clay on the hair side.
