Footage of great apes has revealed that humans are not the only ones to endure seemingly endless bouts of teasing dished out by their smaller and weaker young who appear intent on pushing their luck.
Recordings of chimps, orangutans, bonobos and gorillas found the animals to be masters of the dubious art, embarking on an impressive range of playful and occasionally somewhat aggressive acts ranging from the cheeky and plain silly to the fabulously irritating.
From 75 hours of footage taken at San Diego and Leipzig zoos, scientists documented 142 clear instances of great apes teasing their compadres, with most instigated by juveniles aged three to five years old.
The apes poked, prodded and ran away, offered objects and then pulled them back, body-slammed one other, stuck their faces in others’ faces, pulled on wisps of hair – a move particularly common in orangutans whose hair is amply long enough – tugged on body parts, tickled, and dangled things in front of each other.
And that was only for starters. In all, the researchers in Germany and the US counted 18 different varieties of teasing in the footage. More than a fifth employed an element of surprise, with an ape approaching its target from behind or while it was looking the other way.
“We cannot really say why they are doing it, but we can observe that they are doing it,” said Dr Isabelle Laumer at the Max Planck Institute of Animal Behavior in Konstanz, Germany. “This playful teasing is provocative, intentional, and typically one-sided. It comes very much from the teaser and it often remains that way throughout the interaction.”
As with all the best teasing, a failure to respond to an unexpected poke, or an ape’s face suddenly looming into view, was met with more of the same, with apes repeating their chosen move in 84% of cases or escalating the situation with more elaborate acts of annoyance.
The study of nine bonobos, four orangutans, four gorillas and 17 chimps was too small to find major differences between the species, but adults and juveniles had different strategies. Poking was the most common form of teasing for both adults and juveniles, but while juveniles engaged in hitting and waving body parts at others, adults were gentler and favoured tickling and stealing.
“What’s interesting is we found similarities with human infant teasing,” said Laumer. “When human infants tease their mother, they tend to look to their mother’s face for a reaction. We see that in these great apes too.”
Human infants engage in playful teasing as early as eight months and before they can produce words. Scientists believe the behaviour may help test social boundaries and strengthen relationships.
Although most juvenile apes targeted adults, they often spared their own parents, according to the study in Proceedings of the Royal Society B. There were exceptions, however: Denny the gorilla teased his parents repeatedly, probably because there were few other gorillas around; and Aisha the orangutan became proficient at swinging a rope into her father’s face while he was minding his own business.
It will take more observation to understand why the animals might tease one another. But with the behaviour evident in our closest primate cousins, teasing and the cognitive skills that underpin it may trace back 13m years to the last common ancestor humans share with modern apes, Laumer said.
“Teasing has been discussed in relation to humour, but it can also contribute to understanding social partners,” said Dr Marina Davila-Ross, who studies the evolution of communication at the University of Portsmouth. “If, for instance, a young ape teases another and the second one does not respond, it tells the first individual how far one can go with the second individual, providing vital information about growing up within a social group and establishing hierarchies.”