Polar bears live in an environment in which temperatures plunge as low as -40˚C and where they are frequently diving into the frigid waters of the Arctic Ocean.
While watching a tv quiz show, Prof Bodil Holst of the University of Bergen noticed that polar bears are invisible on infrared cameras, suggesting their fur is extremely cold. But if that was the case, she wondered, why doesn’t the water on their bodies turn to ice?
Phd student Julian Carolan of Trinity College Dublin was tasked with investigating this conundrum, and he discovered that it’s all down to the bears’ greasy fur.
The study found that polar bear sebum, secreted from glands beneath the skin (and which humans and other mammals also possess), was rich in chemicals such as cholesterol, diacylglycerols and fatty acids, which are all water and ice-repellent.
"The identification of physical and chemical characteristics of polar bear fur that enable anti-icing properties promises to inspire the development of more sustainable and environmentally friendly anti-icing materials and surfaces,” notes Carolan in the paper he wrote with a team of experts in Science Advances.
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As well as keeping them ice-free, a polar bear’s greasy fur also allows them to slide quietly over the ice, assisting them in stalking seals, one of their key hunting strategies.
During his research, Carolan discovered that indigenous Arctic people have long known about the slippery properties of polar bear fur. For example, he describes how a hunting stool was fitted with ‘sandals’ made from their fur which allows them to slide it silently over the ice.
The question now is whether other bears’ sebum has the same chemicals – brown bears are closely related, but don’t regularly plunge into freezing water in the same way. “I also wonder if sebum hair oil is partly down to what you eat, and a polar bear has a fattier diet,” Carolan says.
Main image: polar bear swimming through melting sea ice near Harbour Islands in Canada/Getty
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