The hedgehog is covered by about 5 thousand-8 thousand spines, more or less three centimeters long, and close to a millimeter. Under normal conditions the hedgehog holds the spines along the body, pointing towards the tail: in these moments it can be safely caressed without danger of injury. Therefore, during mating the male does not run any risk, because the female completely lowers the spines, so that the partner does not injure the belly. Only when it feels in danger does the animal raise its spines, turning into a pointed ball: particular traction muscles make the skin of the back stretch so that the head, legs and tail disappear completely between the spines.