How do creatures in sub-zero environments keep their metabolisms working?

We put Bruce's question to Kat Arney...

Kat - This is a great question basically because I like polar bears. There's kind of a difference between hot blooded and cold blooded animals. Now, the hot blooded animals, they need to keep a constant body temperature and you tend to get more hot blooded animals in colder places. So for example, they will keep their body size, they have big body size because that means they lose less heat, they have things like fur, lots of blubber. They'll try and eat as much as they can and this helps to keep them at this temperature where their metabolism will work. Cold blooded animals, things like snakes, salamanders, all these kind of things, they will just be the temperature of their environment. So, as the temperature gets colder and colder, and colder, they basically just kind of shutdown. So, turtles and things like that will effectively, if it gets really cold, they'll just stop working. Bigger animals and mammals, they can hibernate and their body temperature does drop. That kind of gets them through the worst of the winter. Scientists are really trying to study this phenomenon to find out, can we maybe put people into a kind of suspended animation if they've had an accident or potentially, as we've talked about, going to Mars. Could that work? Another thing is that the genetics of individual organisms affects their metabolism. So for example, you might make slightly different enzymes that work better at different temperatures. And also, there's different molecules in your cells that can act as anti-freeze and try and keep all your cells and everything going at lower temperatures. So, there's lots of different ways that animals do it. obviously, evolution is a wonderful thing and will adapt each organism to the niche that it lives in. Lots of ways that different animals do that - polar bears mostly by being cute and furry.