Deer, or true deer, is a hoofed ruminant ungulate belonging to the family Cervidae. Key characteristics: Size: Ranges from small species like the pudu (about 30 cm tall at the shoulder) to large species like the moose (over 2.1 meters tall at the shoulder). Color: Typically brown, white, tan, or orange. Diet: Herbivorous, feeding on plants, grass, twigs, and bark. Reproduction: Females usually give birth to one or two young, and males reach sexual maturity at five to six years old. Behavior: Social, often living in small groups, with males sometimes living alone. Examples of deer species: white-tailed deer, mule deer, elk, reindeer, and roe deer.