Why Do Monkeys Steal Other Monkeys’ Babies?

Why Do Monkeys Steal Other Monkeys' Babies?

A scene in David Attenborough’s recent Seven Worlds, One Planet shows the distressing behavior of a female macaque monkey: a childless, high-ranking female steals the baby of another female that holds an inferior position in the group.

The kidnapper does not show mercy even when the baby screams for its mother, who cannot risk getting her baby back, because her low position in the hierarchy could result in her getting attacked. Luckily, the event has a happy end – after the mother of the kidnapped baby starts grooming the higher-ranking monkeys, even the kidnapper does not want to miss out on the fun, joins the grooming session, and brings back the baby.  

Mamma Monkey and her Baby
Mamma Monkey and her Baby

A scene from the Smithsonian’s Monkey Island documentary series depicts a similar event. Depictions like this have a lot of people wondering: Why do monkeys steal other monkeys’ babies? 

Both these situations arose from a childless mother being jealous and curious about another female’s baby. The kidnapping was only short-term in both cases and the babies were reunited with their mothers.

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Stealing another mother’s baby and trying to keep it like yours does not make much sense in a troop, where the members interact a lot, anyway – a kidnapper can hardly lock her victim up and avoid being discovered! 

While the stealing of baby monkeys is not very prevalent, it is quite typical that males who takeover a troop kill the remaining babies. In this way, they make space for the offspring they want to produce and make sure that only the young with their own genetic material remain part of the group. 

It is rare for female monkeys to kill babies, and parents do not usually kill their own offspring, either. There is one exception, though: the mustached tamarins. Being a mustached tamarin mother is not easy. They mostly have twins, which can be quite big, and then have to carry around double the amount of weight the mother of a single baby carries on her back.  

Monkey Carrying Baby Monkey
Monkey Carrying Baby Monkey

Even though the troops care for their young communally, sometimes there is an uneven balance between the number of young monkeys that need care and attention and adult monkeys that can provide these things.

In these situations, there is a greater risk of accidental death, but it also sometimes happens that mothers kill a child by dropping it from a tree or even with a bite in the head.

The make-up of the group and the number of other monkey mothers decide whether this occurs. When a monkey is the only gestating female in the troop, she is going to be lucky, since everyone can pitch in. A troop in which it is safe to raise offspring also needs at least two male monkeys that can protect its members. 

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Do Baby Monkeys Cry Like Human Babies? 

This depends on how we define crying. According to Ad Vingerhoets, a professor of clinical psychology who does extensive research on the topic of tears and crying, humans are the only animals that produce “emotional tears.”

This means that we are the only creatures for whom the emission of tears from our eyes is something that happens during intensely emotional or (physically as well as psychologically) painful moments.

Animals produce tears, too, but not in connection with pain or sadness. Instead, they produce – just like we do, too – tears to moisten the eye or as a reaction to an irritant like sand, wind, or gas. 

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Baby Monkey
Baby Monkey

Most people would agree, though, that crying is not just about tears. In this case, human babies and monkey babies are not so different after all. Monkeys that are in distress or pain or babies that are separated from their mothers vocalize their distress in whimpers, screams, and other sounds that can very well be described as crying.  

Young monkeys are even known to throw tantrums when they do not get what they want. Primatologists have observed that mothers are less likely to ignore their tantrums when being surrounded by other monkeys. Those bystanders, especially when they are of a higher rank, would otherwise become annoyed by the screaming child and start biting, kicking, or pushing both mother and baby.

While being in a public place with a toddler who has decided to throw a tantrum is embarrassing for sure, at least human bystanders are not very likely to attack! 

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Rosa Nowak

Rosa is a German-Canadian writer, a PhD student of English literature, and an amateur natural science enthusiast.