Colloquially, the term "ass" is often used today to refer to a larger, horse-sized animal, and "donkey" to a smaller, pony-sized one. In the western United States, a small donkey is sometimes called a burro (from the Spanish word for the animal).
Although formal studies of their behaviour and cognition are rather limited, donkeys appear to be quite intelligent, cautious, friendly, playful, and eager to learn. They are often pastured or stabled with horses and ponies, and are thought to have a calming effect on nervous horses. If a donkey is introduced to a mare and foal, the foal will often turn to the donkey for support after it has been weaned from its mother.
Once a person has earned their confidence they can be willing and companionable partners and very dependable in work. For this reason, they are now commonly kept as pets in countries where their use as beasts of burden has disappeared. They are also popular for giving rides to children in holiday resorts or other leisure contexts