They give a good impression of the appearance of the earliest predecessors of antler-bearing deer. Their most notable, and unique, feature is the musk bag or pod which develops when the male has reached sexual maturity. This sac, situated between the genitals and the umbilicus, is about the size of a clenched fist. Its glands produce a secretion whose precise function is unknown but which is probably a signal for the females. In contrast to the adults, newborn Musk deer have a distinctly striped and spotted coat.
Musk deer are shy and furtive animals with a keen sense of hearing.
The classification of the Musk deer has long been confused. Fomerly, only one species was recognized, but recently the existence of three different species has been proven. The limits of their distribution are unknown. Musk deer, being primarily forest animals, are never found in desert regions or in areas with a dense human population. Musk deer prefer dense vegetation, especially hills with rocky outcrops in coniferous, mixed or deciduous forests.