Nocturnal, but Communicative
Hedgehogs are easily recognized by their spines, which are hollow hairs made stiff with keratin. Their spines are not poisonous or barbed and, unlike the quills of a porcupine, cannot easily be removed from the hedgehog. However, spines normally come out when a hedgehog sheds baby spines and replaces them with adult spines. This is called "quilling." When under extreme stress or during sickness, a hedgehog can also lose spines.
A defense that all species of hedgehogs possess is the ability to roll into a tight ball, causing all of the spines to point outwards.
All hedgehogs are primarily nocturnal, although different species can be more or less likely to come out in the daytime. The hedgehog sleeps for a large portion of the daytime either under cover of bush, grass, rock or in a hole in the ground. Different species can have slightly different habits, but in general hedgehogs dig out dens for shelter. All wild hedgehogs can hibernate, although not all do; hibernation depends on temperature, species, and abundance of food.
Hedgehogs are fairly vocal, and communicate not only in a series of grunts and snuffles, but sometimes in loud squeals (depending on species).