A mule does not sound exactly like a donkey or a horse. Instead, a mule makes a sound that is similar to a donkey's but also has the whinnying characteristics of a horse (often starts with a whinny, ends in a hee-haw). Sometimes, mules whimper. The coats of mules come in the same varieties as those of horses. Common colors are Sorrel, Bay, Black, and Grey. Less common are White, Roans (both blue and red), Palomino, Dun, and Buckskin. Least common are Paint mules or Tobianos.
The mule possesses the sobriety, patience, endurance and sure-footedness of the donkey, and the vigour, strength and courage of the horse. Operators of working animals generally find mules preferable to horses: mules show less impatience under the pressure of heavy weights, and their skin, harder and less sensitive than that of horses, rendering them more capable of resisting sun and rain. Their hooves are harder than horses', and they show a natural resistance to disease and insects. Many North American farmers with clay soil found mules superior as plow animals, especially in the U.S. state of Missouri, hence the expression "stubborn as a Missouri mule".
Mules are generally less tolerant towards dogs than horses are. They are also capable of striking out with any of their hooves in any direction, even sideways if needed.
Mules exhibit a higher cognitive intelligence than their parent species - horses and donkeys. This is believed to be the result of hybrid vigour, similar to how mules acquire greater height and endurance than either parents.


