Mouse Deer

In other respects, however, they have primitive features, closer to non-ruminants such as pigs. All species in the family lack horns, but both genders have elongated canine teeth. These are especially prominent in males where they project out on either side of the lower jaw, and are used in fights. Their legs are short and thin, which leave them lacking in agility, but also helps to maintain a smaller profile to aid in running through the dense foliage of their environment. Other pig-like features include the presence of four toes on each foot, the absence of facial scent glands, premolars with sharp crowns, and the form of their sexual behaviour and copulation.
They are solitary or live in pairs. The young are weaned at three months of age, and reach sexual maturity at between five and ten months, depending on species. Parental care is relatively limited. Although they lack the types of scent glands found in most other ruminants, they do possess a chin gland for marking each other as mates or antagonists, and, in the case of the water chevrotain, anal and preputial glands for marking territory. Their territories are relatively small, on the order of 13-24 hectares, but neighbors generally ignore each other, rather than competing aggressively.
Some of the species show a remarkable affinity with water, often remaining submerged for prolonged periods to evade predators or other unwelcome intrusion. This has also lent support to the idea that whales evolved from water-loving creatures that looked like small deer.