Hedgehogs are extremely vocal. They communicate their preferences and moods using a repertoire of grunts, chirps, hisses and squeals. When truly threatened, a hedgehog's primary defense is to roll up into a tight ball with all of its spines facing outward. Hedgehogs are nocturnal because most of the tiny animals they feed on are nocturnal as well. (Photo by Traer Scott/Chronicle Books)
