RE: Metatarsal Gland
Metatarsal Glands These glands are a light tan colored circle of hair of about 1 2/3 inches in length located on the outside of the hind leg between the toe and the hock, or heel on whitetails. They are not actual glands, because they have no duct. Mule Deer exhibit the largest glands, then the Black-tailed Deer, and the White-tailed Deer. It has been suggested that blacktails open this gland when alarmed to express danger. It is not totally understood in whitetails, but I have seen it flared when two bucks fight.
I pulled this from another site