The majority of references to deer are specifically to the stag, the male deer. Only a few manuscripts include the doe, the female deer. The doe is sometimes illustrated in company with the stag, but rarely on its own. Bestiary allegory is about the stag.

The stag is the enemy of the snake. When the stag discovers a snake, it spits water into the hole where the snake hides, draws the snake out with its breath, and tramples it to death. If the stag is ill or old, it draws the snake out of hiding and swallows it. The stag then finds water and drinks large amounts of it to overcome the poison, and is renewed. When the stag is renewed it sheds its horns. Some say that the stag cures its ills by eating crabs it finds in the water.

Stags live for a long time; their teeth reveal their age. When Alexander the Great wanted to see how long stags lived, he captured many and had them marked. The marked deer were captured one hundred years later and were still healthy.

When stags must cross a river to find food, they swim in line with one stag's head resting on the rear of the one in front; when the front stag tires, it moves to the end of the line to rest. When stags are struck by arrows, they can shake them off by eating dittany. Stags hear well when their ears are erect, but not when their ears are lowered. They marvel at the sound of a reed pipe, and can be caught by a hunter playing one. Stags are lustful, but the female deer can only conceive at the rising of the star Arcturus. When they hear hunting dogs bark, they change direction to the other wind to keep the dogs from scenting them.

The name hinulus, young deer or fawn, is similar to the name hinnulus used for the mule.

The stag is a symbol for Christ, who tramples and destroys the devil. As the stags crossing a river help each other, so should the Christian crossing from the worldly life to the spiritual life help others who grow weak or tired. As the stag is renewed and sheds its horns after drinking from the spring, so those who drink from the spring of the spirit are renewed and shed their sins.

People who eat venison are protected from fever because stags are never feverish. The smoke from burning stag antlers stops an attack of epilepsy and is deadly to snakes. The right antler is the best for medicine. A drink made from the tears and the heart bones of a stag is a cure for troubles of the heart. An ointment made from a stag's marrow reduces fever. The marrow also soothes pain in the limbs. A stag horn ground to powder and mixed in a drink dries up all fluids. The same powder rubbed on teeth strengthens them, and when mixed with wine cures decay and destroys stomach worms. A person wearing a stag's skin does not need to fear snakes. A stone found in a stag's belly can help women conceive.

Hildegard von Bingen says, "If a person eats the flesh of the deer when it is a bit hot, but not burning, it will purge his stomach, making it light. Shave some of its horn, add frankincense, and burn them together over a fire. The horn’s power gives off an odor that chases off airy spirits, spells, and bad worms and checks magic. If a person eats deer liver, it will restrain his gicht [gout] and purge his stomach, making it light." (Throop translation)