Female baboons love to talk about sex, particularly when it's good. Biologists have been baffled by this bawdy habit, but new research suggests that the ladies may have a good reason for being so forthcoming.
Grunting in approval.
CREDIT: ROBERT THOMAS AND MARGARET ORR/CALIFORNIA ACADEMY OF SCIENCES
Unlike lots of other animals that call, sing, or whistle to advertise fertility but fall silent after the deed is done, female baboons give loud staccato grunts after mating. The grunting tends to be more intense after sex with a higher-ranking, dominant male. Researchers previously thought the calls to be a signal encouraging more males to compete for a roll in the hay. But behavioral biologist Dario Maestripieri of the University of Chicago and his colleagues say the female's postcoital grunts are intended to make her partner stick around.
Maestripieri's team studied a captive group of Guinea baboons at the Brookfield Zoo in Chicago for 3 months and found that instead of persuading more males to mate, a female's calls put off potential suitors. Once a female baboon mates with a preferred male, it is in her best interest to give that male's sperm the best chance to fertilize her eggs by avoiding further copulation. Males comply by guarding a female that's grunted. This tactic gives female baboons--who might otherwise be at the mercy of the much larger males--a say in who fathers their babies, Maestripieri reported at the Animal Behavior Society meeting in Boise, Idaho, last month.
"It's definitely a novel take on postcopulation calls," says Fred Bercovitch, a behavioral biologist at the Center for Reproduction of Endangered Species at the San Diego Zoo. But before Bercovitch will be convinced that the behavior has an adaptive purpose, he says more work is needed, such as tallying whether the calls actually decrease the number of males a female mates with during her most fertile days.
