May 21, 2007 — With the male grunting and the female emitting loud and long operatic calls, mating chacma baboons produce an incredible amount of noise. And a new study has found that other males take advantage of the din by eavesdropping on mating couples to determine the status of relationships.
If the couple quarrels or parts, for even just a brief moment, the snooping male then takes advantage of the situation by mating with the female, himself.
"For male baboons, copulation calls are the most interesting vocalizations because they are only given by females and are clearly associated with females mating," lead author Catherine Crockford told Discovery News.
Crockford, a researcher in the University of Pennsylvania’s Department of Psychology, explained that eavesdropping sometimes provides low-status male baboons with such mating opportunities, since higher-ranked, more dominant males otherwise monopolize high-ranked females.
High-status baboons form what are known as consortships, which can last for a few hours up to a week. During this mini marriage-like period, the male follows a female closely and guards her against other approaching males.
When the couple begins to noisily mate, Crockford said the eavesdropping males "must make deductions from the calls they hear about who is doing what with whom."
She and her team studied a troop of free-ranging baboons in the Moremi Game Reserve of Botswana. The researchers observed lower-ranked males and waited until the animals were minding their own business, such as resting or nibbling on a palm nut or some sausage fruit.
The scientists then played a male grunt out of a loudspeaker followed by a female copulation call played out of another speaker placed over 131 feet away. Since females will continue to call when they possess sexual swellings linked to ovulation, the speaker setup mimicked what would happen if a mating consort pair separated.
The noises prompted the lower-ranked males to literally drop what they were doing and to rivet themselves towards the speaker emitting the female copulation call.
