The most noticeable difference is of course the ears. Donkeys ears are much longer in proportion to their size than a horse' s, and their necks are characteristically straighter. Donkeys have only five lumbar vertebrae compared with most horses six, and generally have upright, sparse, spiky manes with no forelock. They evolved in the desert, so they have tough compact hooves that can handle sand and rock, woolly hair to insulate from heat and cold, a lean body mass that is fuel efficient, yet very strong and enduring, and a digestive system that can break down almost inedible roughage while at the same time extracting and saving moisture. Donkeys come in various colors, but the most common is the mouse gray called gray dun.
Donkeys have a strong sense of survival.
If they deem something as dangerous, they won't do it. And, they are smart enough to know when they can't handle something. If they hear a strange noise, donkeys sound an alert. Donkeys often even chase and trample the predators.