Sleeping off a tough winter to survive

Winter is upon us. Many birds fly south to avoid the cold wet darkness, but migration isn’t an option for mammals. They have to make do with thicker coats and extra layers of body fat, writes Richard Collins

An animal failing to pay its heating bills, goes to the wall. Size matters; large objects retain heat better than small ones, so being big and bulky helps.

Wild creatures feed up in autumn when food is plentiful. Hibernation makes body-fats go much further, but storing enough fuel, in advance, for an entire winter isn’t easy.