That issue of preferred associates comes close to the human notion of friendship, and it can prove just as important in understanding animal goings-on as it does in people watching. Baboons, bats, and dozens of other animals have been studied from this perspective. Biologists may start by asking whether individuals prefer to hang out with particular buddies. But other questions soon pop up. Does the sex or kinship of a companion matter? Are there benefits to the association? The answers