Public tantrums defeat monkey mothers, too: bystanders make macaques more likely to give in to baby.

Baby screams. Onlookers glower. Mom gives in--even when she's a monkey.

Rhesus macaque mothers are about twice as likely to let a howling infant have its way during very public tantrums than during more private moments, says Stuart Semple of Roehampton University in London.

Not a bad decision on mom's part. A baby macaque lets out a high-pitched shriek that makes onlooking monkeys restless. Mom and the unhappy baby become at least 30 times more likely to suffer aggression from a bystander during a crying bout than in quiet times, Semple and colleagues report online March 10 in Proceedings of the Royal Society B.

Studies of communication often focus on just two parties, the one sending the message and the intended receiver, Semple says. But the real world is full of other eyes and ears. "We need to start thinking about communication in more realistic terms," he says.

[ILLUSTRATION OMITTED]

This tantrum study "adds a new dimension of complexity to our understanding of mother-infant communication and mother-infant conflict in primates," says Dario Maestripieri of the University of Chicago. Research has found that nonhuman primates pay attention to eavesdropping bystanders, "but this is the first demonstration that communication between mother and infant is affected by an audience," Maestripieri says.

Semple and his colleagues studied rhesus macaque tantrums by watching monkeys on the island of Cayo Santiago, Puerto Rico. Infants wanting to be nursed when mom wasn't willing often started shrieking. For more than 300 outbursts of baby crying, observers noted which other monkeys, if any, were within two meters. The team also noted how mom, baby and the bystanders interacted.

Semple and the researchers picked two meters because both male and female bystanders within that range routinely reacted visibly to bawling babies. The onlookers occasionally made threatening gestures, or even chased, grabbed or bit the mother or the infant.

When morns and babies weren't close to other monkeys, rebuffed babies that started shrieking were allowed to nurse 39 percent of the time, the researchers found. With just relatives nearby, the babies' luck rose to 54 percent. But with unrelated onlookers that outranked mom in the dominance hierarchy, babies won the tantrum 82 percent of the time.