### animal | vertebrate | mammal | ungulate:

Mule
* Most mules have skin
  - tails
* Some mules do require shoes, depending on their terrain
  - possess resistance
* also resist disease well
  - seem to have fewer leg soundness problems than horses
  - tend to be more independent than most domesticated equines other than the donkey
* always tend to have a ball with coat coloration and markings.
* appear to be quicker and more accurate problem solvers than horses or donkeys.
* appear to suffer from an aggressive form of sarcoids
  - disease and accidental injuries less than horses
* are a cross between a donkey and a horse
  - distinct species because they produce fertile offspring when mated
  - always sterile because horses and donkeys have different chromosome numbers
  - animals
  - generally more intelligent than horses
  - good examples of hybrid sterility
* are hybrids and, like all true hybrids, are generally unable to reproduce themselves
  - with interspecific sterility
  - intelligent and possess a strong sense of self-preservation
  - mammals
* are more common , and have been used for transportation of people and things
  - intelligent than donkey's or horses
  - of such ancient origin in the Middle East that their exact beginnings are murky
  - pack animals
  - slippers
  - sociable, gregarious and less quarrelsome than horses
  - software
  - sterile but female mules are known to produce milk
  - strong-willed animals
  - stronger than horses, with much longer working lives
* are the adulterous offspring of the horse and the ass
  - hybrid product of a male donkey and a female horse
* are the offspring of a jack and a female horse
  - male donkey and a mare
* are the product of a mating between a horse and a donkey
  - mating a horse and a donkey
  - very hardy animals
* blink long lashes in the dusk, tied up and resting.
* can be stubborn at times, but they are the best in extreme heat
  - bray like donkeys or whinny like horses
* come in both male and female.
* eat less than horses do.
* excel in physical soundness.
* form close bonds with horses, especially mares.
* get their natural abilities from the donkey.
* have a strong sense of self preservation
  - backs that are much straighter than horses' backs
  - fewer feeding problems than horses do
  - longer ears than horses but usually somewhat smaller than donkey
  - more stamina
  - their uses as do dead horses
  - breasts
  - cells
  - heads
  - hoofs
* is an equid
* live longer productive lives than horses do.
* overheat only in extreme temperatures and when overworked.
* require the same vaccinations and parasite control as horses.
* sometimes whimper.
* tend to be healthier, heartier and longer-lived than horses
  - develop trusting relationships with the rider or trainer
+ Donkey: Equids :: Domesticated animals :: Animals used for transport
  * Donkeys can have hybrid children with a common horse. The child of a female horse and a male donkey is called a 'mule'. The child of a female donkey and a male horse is called a 'hinny'. Mules are more common, and have been used for transportation of people and things.
+ Hybrid: Classical genetics :: Green vehicles
  * A 'hybrid' is the product of mating between individuals of different species or strains. The word is most common when talking about plants and animals. Mules are hybrids. The female parent is a horse and the male parent is a donkey. The result, a mule, is sterile.

Other ungulate
* inhabit terrains.
* share habitats.