Young vervet monkeys look to mom when learning

Vervet monkeys can learn from each other. Last year, Science News reported, scientists showed that young male monkeys are capable of social learning: When they leave the group in which they were born and join a new group, they can pick up behaviors from their new compatriots. “Trying to be like others is a way of bonding with another group,” said cognitive biologist Andrew Whiten of the University of St. Andrews in Scotland.

Scientists call that horizontal learning, a transfer of information across individuals belonging to the same generation. But the more common pathway is probably vertical, that is, from one generation to the next. And now researchers have evidence that this type of learning does happen in wild vervet monkeys — children learn from their mothers, Erica van de Waal of the University of St. Andrews and colleagues report in the April Animal Behaviour.

In an earlier study, van de Waal and Whiten had documented the various ways vervet monkeys handled a problem — cleaning off tasty grapes covered with sand. The monkeys had five different approaches: rubbing the grape with their hands, rubbing the grapes on something to remove the sand, peeling the grape with their teeth and eating only the interior, peeling the grape with their hands, or just eating the grape, sand and all.

The researchers wanted to know if young vervet monkeys could learn how to eat a sand-covered grape by watching mom or someone else. They worked with a group of wild but habituated vervet monkeys at Loskop Dam Nature Reserve in South Africa. And they watched what happened after they gave a group of monkeys a box full of sandy grapes.

During their study, which lasted several years, they were able to see how 17 young vervet monkeys dealt with their first sand-covered grapes. Sixteen of the 17 mimicked their moms, and the seventeenth, named Ivy, copied her older sister India. But India was essentially Ivy’s mom at that point (the researchers called her a “mother-substitute”), so it was clear that what mom did was the key piece of information. Even when other monkeys were present, the infants always looked to their mothers for what to do.

“The first grape eaten was invariably processed exactly the way the mother processed her grape immediately before the event, consistent with social learning,” the researchers write.

Several of the mothers were seen using two or more methods to clean their grapes. The babies always copied the most recent method used when approaching their first grape. After that, though, those infants tended to mimic their moms and use multiple methods, too.

Some scientists had thought that dominant monkeys might be more important role models, but this study confirms the importance of mom. That said, van de Waal and colleagues don’t think that young monkeys only learn from their mothers, but she’s probably the primary source for learning how to get on in life. Human mothers would probably agree that this is a good learning strategy when kids are growing up.