Photo by Jenny E. Ross, Courtesy of Dr. Bodil Holst

February 13, 2025

by Robin Oliverio, Ph.D.

Polar bears are full of contradictions: they are warm on the inside, but their outside is as cold as their surroundings; they are friend-shaped but not friendly; and they spend time in arctic waters but their fur is not icy. This year, researchers might have revealed the answer to this last contradiction. Julian Carolan and colleagues published a paper in the prestigious journal of Science Advances that suggests polar bear fur has some built-in anti-icing properties.

As mentioned above, the internal body temperature of polar bears is pretty high at around 98.4℉ (36.9℃) But if you were to pet a polar bear (and don’t pet a polar bear), you would find that their fur is really cold. This is because they are really well insulated with blubber and they have two layers of fur. Basically, they’re all bundled up with their own personal coats. What has baffled scientists for such a long time is how they keep their cold fur from being icy while thriving in a cold, aquatic environment. Dr. Bodil Holst, who was the corresponding author on this paper, said she was inspired while watching a German quiz show. A piece of trivia shared on the program was that polar bears are invisible on infrared cameras. This is because infrared cameras use heat for detection, and the polar bear fur is so cold that it blends with the surroundings.

The paper by Carolan and colleagues suggests that the polar bear sebum may be the root of this anti-icing capability. Sebum is an oily substance that surrounds the hair follicle, and like polar bears, we also have sebum that collects around the roots of our hair. The researchers demonstrated that certain compounds in the polar bear fur sebum do not adhere very well to ice, like cholesterol. Emphasizing its necessity to prevent icing, when these scientists washed the fur to remove the oil, they found that ice did form on the fur.

Now, if you are thinking of not showering all winter in order to maximize the anti-icing properties of your hair, I want you to stop right there. It is important to note that there are some key differences between the sebum found in human hair and that found in polar bear fur.

One key molecule that the scientists found was not in polar bear fur sebum was squalene. This compound is found in human hair sebum as well as the sebum of many other aquatic mammals. Interestingly, they found that squalene actually adsorbed very well to the ice, meaning it was easier for the ice to form bonds with this compound as opposed to other molecules that were present in the polar bear fur sebum.

Photo courtesy of Dr. Bodil Holst, Carolan et al., 2025

Polar bears utilize this special anti-icing function of theirs to improve their daily life. When hunting, the polar bears sometimes slide across the ice to sneak up on seals. If their fur did adhere well to the ice, that would cause friction as they slid, and friction is noisy. Native Arctic cultures knew about this anti-icing function of polar bears and also used it to improve the success of hunting. They would put polar bear fur on the legs of stools, and use this to slide across the ice so they too could be stealthy and not alarm their targets.

It is fascinating how different microscopic aspects can vary the way a material interacts with another material. To make a bad pun, polar bear fur is pretty cool.

About Robin Oliverio, Ph.D.

Robin holds a Ph.D. in neuroscience and is passionate about bridging the gap between science and policy. She focuses on using research to inform evidence-based policies that drive positive societal change. She is strongly committed to projects that make a meaningful difference in people’s lives, and she thrives in roles where science meets advocacy, communication, and impact.

If you have any questions or would like a particular topic to be featured, please reach out to Robin Oliverio, Science Communications & Media Specialist, at OliverioR@CarnegieScienceCenter.org