Animal skins and hides treated to preserve them and make them suitable for use. Tanning converts the otherwise perishable skin to a stable and nondecaying material. Though the skins of such diverse animals as ostrich, lizard, eel, and kangaroo have been used, the more common leathers come from cattle, including calf and ox; sheep and lamb; goat and kid; horse, mule, and zebra; buffalo; pig and hog; and seal, walrus, whale, and alligator. Leather making is an ancient art that has been practiced for more than 7,000 years. See alsoparchment.