Researchers at the University of Sheffield and the Leibniz Institute for Zoo and Wildlife Research in Berlin said animals generally avoid inbreeding by either moving away from home or, as do humans, avoiding mating with relatives.

Since male hyenas don't contribute to the rearing of their offspring, it's unlikely females know their father. Instead, males decide to leave the group in which they were raised, resulting in a low level of inbreeding.

But little has been known about why the males -- and not females -- move from home. The new research involving spotted hyenas shows males move because of the rules females use when choosing which of the many male group members will sire their offspring.

Researchers found young females prefer mating with males born into the group or who joined it after the female was born. Older females prefer males that have built friendly relationships with them for several years.

Such mate preferences mean males must choose groups with a high number of young females if they want to successfully reproduce.

The study appears in Nature magazine.