How to

2 June 2016

How They Keep Warm: Polar Bears

Polar bears are absolutely massive, by far one of the largest land animals in the arctic. An adult male can weigh up to 750kg, which is a little bit more than a Smart Fourtwo. Yep, a car, a small car granted, but still a car. They need to consume an average of about 2kg of fat per day in order to maintain the energy to propel their massive bulk across the ice.

They are also one of the most solitary animals in the Arctic, spending the vast majority of their lives roaming across their territory completely alone. Penguins might be able to rely on each other to stay warm, and walruses and seals bask on the shores in big groups, but polar bears have no such social luxury.

That in mind, how exactly do they stay warm when temperatures in the Arctic Circle can drop as low as −50°C? As is often the case with arctic animals, the bears have a layer of blubber which traps warmth, in their case it’s about 10cm thick. There’s a further 15cm of fur on top of that. That’s a lot of insulation, even on a fundamental level, but it doesn’t fully account for how warm polar bears are able to stay. They are so well insulated, in fact, that they don’t show up on thermal cameras.

Until recently, it wasn’t exactly clear why this was, but recent research has revealed that polar bears process the nitrous oxide in their bodies in a different way to other bears. They are able to produce more of it, which means that they are able to convert energy that would normally become metabolic into heat energy. This is why they primarily prey on seals – more blubber equals more carbohydrate.

When they aren’t out and active, the bears will burrow into the snow for warmth. While snow is made up of cold icy crystals, they trap air in between, so a layer of snow can actually act as an insulating blanket. They will do this when they enter their ‘winter sleep state’, which is almost a halfway point between hibernation and torpor. They will sleep, deeply, but they can still be woken if they need to be.

Polar bears also have an edge in the surprisingly warm summer months (which can reach up to 30°C), as they moult much of their thick winter fur. They also swim in the icy water in order to lower their body temperature, and even change the way they move, widening their stance to allow more heat to escape. 

Callum Davies

Callum is a film school graduate who is now making a name for himself as a journalist and content writer. His vices include flat whites and 90s hip-hop.