What is a deer bellow?

A deer bellow is a low-pitched, resonant vocalization produced by male deer during the breeding season. It is a territorial call that serves to attract females and warn off potential rivals. The bellow is typically produced by mature males, although younger males may also attempt to bellow. The sound is produced by vibrating the vocal cords in the larynx, and is amplified by the deer's large chest cavity. The bellow can be heard from several kilometers away, and is often used by hunters to locate deer.