The body of adult hedgehogs ranges from 14 to 30 centimetres long, and their tail can add one to six centimetres. When they are born (there can be up to seven in a litter) their spines are soft and short. But soon after birth, their spines harden, becoming stiffer, sharper and longer. Babies stay in the nest until they”re about three weeks old. By that time, their eyes are open, their spines are effective and they can safely follow their mother outside the nest as she looks for food.