New World Deer (Capreolinae)
Roe deer and caribou are part of this subfamily of deer. Both the smallest--pudu--and the largest--moose--deer species on Earth belong to the Capreolinae subfamily. There are 22 modern species of New World deer, including the most widespread deer species, white-tailed deer. The habitat of 18 of these species is in North and South America. The other four species live in Europe.
Old World Deer (Cervinae)
The Old World deer subfamily includes wapiti, American elk and red deer--the only deer species indigenous to Africa. Munjacs are sometimes included in this subfamily. All species of Old World deer exist in Europe or Asia, except for red deer. When Old World deer species shed their antlers, a new pair of antlers begins growing immediately. New World deer have a resting period between antler growths.
Water Deer (Hydropotes inermis)
Water deer are indigenous to China and Korea, but live in Europe and the United States as well. Their name comes from the fact that water deer are capable swimmers. They can swim for more than a mile when they require a new food source or bed.
Water deer are distinctly different from other deer subfamilies in two ways. Water deer do not grow antlers and they possess large canine teeth that extend below the lower jaw. These canines can be more than three inches long.
Muntjacs (Muntiacinae)
Muntjacs or barking deer are small deer that bark as dogs bark. They are the oldest deer subfamily on Earth. The smallest specimens weigh little more than 22 pounds. Muntjacs are native to Asia, but have spread to Europe.
Unplaced Deer
Deer of the genuses Dicroserus, Euprox and Heteroprox have no subfamily. They are also all extinct. These genuses date back to the Oligocene and Miocene epochs.