A large bovid (family Bovidae) that was domesticated in southern Asia from a wild ancestor (B. arnee), which is now endangered. Water buffalo are black or slate-grey and have long, curved horns growing approximately horizontally to the sides of the head. River buffalo spend much of their time in deep water, and swamp buffalo in mud holes. Both types feed on aquatic plants, often with their heads submerged. Water buffalo are raised throughout southern Asia for milk, meat, and as draught animals, and they have been introduced to southern Europe, South America, and Australia; there are a few in the USA.