Bucks: Fight among themselves and issue repeated calls, known technically as groans, during the rut.
Does: Pick a mate by listening to the males' groans.
Scientists: Have determined what females listen for. Researchers at the University of Zurich found that the acoustical properties of a buck's groan are related less to his size than his social rank—and that does mate with a dominant buck more often. It's the first time auditory discernment of social dominance has been found in animals other than primates.