What's the difference between a mule deer and a white-tailed deer?

Here are the general descriptions of each species from the online Animal Field Guide at http://fwp.mt.gov/

fieldguide/, which was created through a partnership between Montana Fish, Wildlife and Parks and the Montana Natural Heritage Program.

Mule deer

Coat gray in winter, brownish in summer; forehead and brisket dark; chin, throat, and rump patch white; tail short and round with black tip; ears large (reason for name); antlers fork and fork again; typical adult buck has four tines on each side (or five if brow tines are present); forward-tipping brow tines are shorter than those of whitetails or may be absent; outside of hind foot has a slit-like scent gland up to seven inches long; mature bucks weigh 250-275 lbs. on good range, does 160-180. More gregarious and migratory (mostly elevational movements) than white-tailed deer; feed early and late in the day; run with tail down in bounding leaps, keeping all feet together.

White-tailed deer

Coat grayish-brown in winter, reddish-brown in summer; underside of foot-long tail white; antlers consist of main beams, generally with three to five tines projecting upward; brow tines long; outside of lower hind foot has a small, teardrop-shaped scent gland; mature bucks weigh 250-275 lbs. on good range, does 160-180.

Occupy small home ranges, do not migrate far; mostly nocturnal and secretive; solitary much of the time but form small groups in favored feeding areas; when alarmed or running, erect and wag their tails, causing white underside to flash.