Baboon siblings get jealous just like human kids: scientists

A baboon, right, cools off with ice cubes containing mint juice at the Zoo of Vincennes in Paris France, Thursday, Aug, 2, 2018.

Sibling rivalry isn’t just a problem for humans -- young baboons also compete for their mother’s attention, scientists said on Wednesday.

The scenario is familiar for many parents: just when they finally get to share a special moment with one of their children, a little brother or sister pops up trying to get noticed.

Axelle Delaunay, an evolutionary biologist at Finland’s University of Turku and lead author of a new study, told AFP that jealousy is a “very striking” emotion in humans.

However, it has been little studied among our fellow primates because jealousy is “very complicated to measure”, she said.

Female primates usually only have one baby at a time, so “it was generally thought there was no real competition between siblings, because brothers and sisters are different ages and do not necessarily need their mother and her resources at the same time”, Delaunay explained.

For the study, a team of researchers observed two troops of wild chacma baboons in Tsaobis Nature Park in central Namibia between August and December 2021.

There were 16 families living in the troops, with a total of 49 young siblings.

Baboons live in societies ruled by women, with the position of power handed down from mother to daughter. Males, meanwhile, leave after puberty.

Like humans, baboon infants have a long developmental period during which they maintain strong bonds with their mother.

The mothers often groom their children -- and have been known to play favourites.

So the scientists spent lots of time watching baboon mothers either resting or grooming their children.

They meticulously noted when another infant interfered with a mother’s grooming by biting, slapping, crying out or more gently asking for affection.

What they observed “strikingly mirrors patterns of sibling jealousy reported in humans”, according to the study published in Proceedings of the Royal Society B: Biological Sciences.

The young baboons were more likely to interrupt their mother when she was grooming one of their siblings than when she was just resting.

The scientists also developed an index to show how the mothers played favourites, choosing to groom some kids more than others.

Delaunay pointed out that the displays of sibling jealousy did not appear to offer “many immediate benefits”.

Baboon mothers only stopped grooming one of their children because of an outburst from another roughly one-fifth of the time, the scientists found.

And she only then started grooming the jealous child nine percent of the time.