In nature, water crystallises to form ice at about 0°C and it is largely this, rather than temperature, that poses a mortal danger. When ice forms, cells are ruptured by the expansion, or pierced by the growth of sharp crystals.
How do animals survive freezing temperatures?
Many insects prevent ice forming by dehydrating their bodies. North America’s wood frog can famously go weeks below zero and withstand –14°C, because its blood is high in natural cryoprotectants such as urea, glycerol and glycogen. These work like antifreeze, bonding so strongly with water molecules that they cannot bond with each other to form ice crystals.
Can any mammals survive freezing?
The only mammal able to cool below zero is the Arctic ground squirrel. During an eight-month hibernation, its core temperature falls to –2.9°C. It survives by ‘supercooling’ itself, so that water in its body is unable to form crystals around a nucleus and freeze solid.
Are there any insects that can survive freezing?
Did you now there are some worms that can live in ice? These cold-loving creatures are the only annelids that spend their entire lives in glacial ice. Ice worms require chilly temperatures of around 0 ̊C to survive. Special antifreeze proteins prevent them from becoming ‘wormsicles’, and they are able to overwinter deep inside snow-insulated glaciers. If exposed to the balmy warmth of 4.4 ̊C, their membranes dissolve and they will melt into goo.
Ellen Husain
Main image: Arctic ground squirrel © Getty Images