Skunk species vary in size from about 40 to almost 70 centimetres, and in weight from about half a kilo (the spotted skunks, genus Spilogale) up to as much as 6 kilos (the well-known Striped Skunk of North America). All species share a similar form: a moderately elongated body with resonably short, well-muscled legs, and long front claws for digging.
They are nocturnal carnivores: they eat a great many insects and their larvae, especially by digging for them, and they are keen mousers. Frogs, salamanders, bird eggs, snakes, and carrion are also important. In settled areas, human garbage is sought.
Skunks are solitary animals when not breeding, but may gather together to keep warm in communal dens in the coldest part of their range. During the day they shelter in burrows which they dig with their powerful front claws, or in other man-made or natural hollows as the opportunity arises. Both sexes occupy overlapping home ranges through the greater part of the year; typically 2 to 4 km2 for females, up to 20 km2 for males.
Breeding usually takes place in early spring. Females excavate a den ready for between one and four young to be born in May. The male plays no part in raising the young and may even kill them. By late July or August the young are full-grown and disperse.
Although they have excellent senses of smell and hearing—vital attributes in a nocturnal carnivore—they have poor vision. They cannot see objects more than about 3 metres away with any clarity, which makes them very vulnerable to road traffic. Roughly half of all skunk deaths are caused by humans, as roadkill, or as a result of shooting and poisoning. They are short-lived animals: fewer than 10% survive for longer than three years.
The best known and most distinctive feature of the skunks is the great development of their scent glands, which they use as defensive weapons. They have two glands, one either side of the anus, which produce a highly offensive mixture of methane and butane compounds flavoured with sulphur. Muscles located next to the scent glands allow them to shoot out the liquid quite accurately to a distance of about 2 metres. The smell aside, it can cause irritation and even temporary blindness, and is sufficiently powerful to be detected by even an insensitive human nose anything up to a kilometre downwind.
Their chemical defence, though unusual, is effective. Predators like owls, foxes and badgerss rarely kill them. Because skunks have only enough scent for 5 or 6 'reloads' and take a couple of days to refill their scent glands, they are reluctant to expend their 'ammunition'. This is why skunks have such bold black and white colouring: to ensure that so far as predators are concerned, they are as visible and as memorable as possible. Where practical, it is to a skunk's advantage to simply warn a threatening creature off without expending scent: the black and white warning colour aside, threatened skunks will go through an elaborate routine of hisses and foot stamping and tail-high threat postures before expelling a shower of scent.
This ability has not escaped the attention of biologists: the name of the most common species, Mephitis mephitis, means 'stench stench', and Spilogale putorius means 'stinking spotted weasel'.
Skunks are closely related to the weasel group and although they are now generally classfied as a separate family within the same order, some taxonomists still place them as a subfamily of the Mustelidae.
Domesticated skunks can legally be kept as pets in certain U.S. states. Some skunks were reported by European settlers in America as being kept as pets by certain Native Americans.