Musk

Musk is an oily substance secreted by special glands in most mammals, notably in canids, mustelids, and mephitids. For any creature to whom smell is an important sense, musk is an easy way of identifying a species or individual. For those species with an especially potent musk, it may function as an announcement or warning of the animal's arrival. The musk of mephitids may serve as a defensive weapon.