Within 36 hours, their brown prickles start to come through.
When fully grown they will have 5-6000 prickles. They are modified hairs and hollow. This makes hedgehogs very good swimmers as they are buoyant, they drown because they cannot get out of the water. Prickles moult like our own hair and, when raised, they all point in different directions, thus making it very painful for predators to attack them. The prickles are also used for nest making. They turn round and round in their nesting material, raising and lowering the prickles as they go and knitting the loose material together.