How to

3 June 2016

How They Keep Warm: Arctic Woolly Bear Moth

To some extent, it’s easy to understand how warm blooded animals stay warm in arctic temperatures. Most rely on a thick layer of blubber to retain the heat already stored in their bodies, but what if you’re cold blooded? More than that, what if you can’t even depend on skin, because you have an exoskeleton? There are actually a few different invertebrates which live in the Arctic Circle, mostly flies and bees, but there’s one particular animal which has developed some amazing cold weather adaptations – the arctic woolly bear moth.

It might sound like somebody just smashed a bunch of random animal terms together, but trust me it’s a real thing, and it’s remarkable. When you live in a cold environment with none of the hard earned adaptations that your fellow residents have, there’s only one way to live – slowly. While they’re referred to as moths, the arctic woollies actually spend most of their lives in caterpillar form as seen above, and in fact they actually spend 90% of their lives frozen.

With their cold blood, the caterpillars need the temperature to be between 15°C and 30°C, and since the North Pole only gets that warm for a very brief period in the summer months, all they can do until then is, well, nothing. During the time when they can actually move freely, there are two things on the schedule – eat and, eventually, pupate. Given the time frame, this can take up to 7 years.

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The adult moth only lives for about 2 weeks, during which time it simply mates and lays eggs, it doesn’t even eat. In some regard, the moth gets the easier deal, as it isn’t alive long enough to have to deal with the deep freeze. The caterpillar does, and it’s evolved a whole arsenal of adaptations to do so. It is just about the hairiest caterpillar in existence, and this coating is able to retain the heat they pick up whilst basking in the sun, improving their metabolism.

Perhaps most impressively though, their blood and body tissue is lined with special cryoprotectant chemicals to stop the parts which need to keep working from freezing up when the temperatures drop to 70 below. These include glycerol and betaine. The caterpillar accumulates these chemicals by allowing the mitochondria (which are responsible for respiration and energy production) in their cells to break down, only to build back up once it gets warm again. 

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.