Despite their horns, stag beetles are herbivorous, tearing down whole trees and digesting the wood by use of an enzyme which is disgorged from their stomachs. This enzyme is of no danger to humans. The stag beetle will react very aggressively if disturbed, however, attacking by swinging its huge horns at beasts and others; most creatures are driven off in this fashion without loss of life. Occasionally a stubborn predator will die, but the giant stag beetle will not touch the body once it has ceased moving.
The "antlers" of the stag beetle are usually half the beetle's full length, or seven feet. They can be opened and closed slowly. The stag beetle will usually open them as a threat to others a round before attacking.
Stag beetles do not normally associate together. However, one species, commonly called a scarab, native to Egypt, has been seen to congregate in very large numbers.