No tantrum. This macaque infant got what it wanted.

Stuart Semple

Lesson to Monkey Mothers: Don't Ignore Tantrums

It's the nightmare of every parent: your child throws a tantrum in a crowded supermarket because you won't buy his or her favorite candy. But things could be worse. The crowd could start attacking you and your child. It turns out that's just what happens in one rhesus macaque society. When a mom doesn't give in to her baby's demands, it risks being smacked and bitten by its fellow monkeys.

Rhesus monkey babies cry when they want to nurse. If a mother ignores her child for too long, the baby will begin flailing and screaming (see video). Curious about how monkey onlookers respond to these tantrums, primatologist Stuart Semple of Roehampton University in London and colleagues followed a wild troop of rhesus monkeys on Cayo Santiago, an island off the coast of Puerto Rico. For 4 months, Semple's team observed the interactions among 11 females, their young infants, and other members of the troop.

Whether a baby got its way depended on who was around when it threw its tantrum. If the mothers were alone or only close relatives were nearby, the moms acquiesced to the baby's outbursts only about 40% to 50% of the time, the team reports online today in the Proceedings of the Royal Society B. But when highly aggressive macaques--those with a history of violence and those higher than the mother in the group's pecking order--were near, mothers gave in 82% of the time. "Bystanders affect the outcome of temper tantrums quite significantly," says Semple.

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Waaa! Watch a baby macaque throw a temper tantrum.

The reason for the disparity, says Semple, is that high-ranking monkeys are 35 times more likely to kick, bite, and shove mothers and babies when a child is having a tantrum than when it is well-behaved. "They do it basically because they are annoyed by the sound." So when hostile monkeys are around, mothers cave to tantrums to reduce the risk of harm.

Researchers already knew that monkey mothers modify their behavior in the presence of aggressive comrades, says primatologist Dario Maestripieri of the University of Chicago in Illinois. For instance, when babies get close to potentially dangerous individuals, mothers start scratching themselves as a sign of anxiety and retrieve their infants as quickly as possible. But this study is the first to show that a mother will alter her interactions with her baby based on who's around, he says.