There are about 50 species of deer including elk, moose, caribou or reindeer, muntjac, red deer, and white-tailed deer, among others.
Deer are native to Europe, Asia, North America, South America and northern Africa. Humans introduced deer to Australia, New Zealand and South Africa.
A characteristic of deer is that almost all species have antlers, a biological structure that is unique to deer. Other ruminants have horns. Antlers consist of bony outgrowths from the head with no covering of keratin as is found in true horns.
Most species of deer live in forested or partly wooded areas, although some live in grasslands, marshlands, and tundra. Deer range from very large to very small.
The moose or elk is the largest species in the deer family. It can grow up to 2 meters (6.5 feet) from hoof to shoulder and weigh around 820 kilograms (1,800 pounds).
The Southern pudu is smallest species in the deer family. It weighs only around 9 kilograms (20 pounds) and gets to be only around 36 centimeters (14 inches) tall when fully grown.
The lifespan of deer is from 10 to 25 years depending on the species; though many die long before then due to predators or environmental dangers such as collisions with cars.