Orangutans act out meaning in a behavior that was previously thought to be uniquely human.
Orangutans pantomime in order to communicate with humans and other apes.
The mini charade-like displays feature characteristics of language.
Other great apes, such as gorillas and chimpanzees, also pantomime.
Orangutans, of their own volition, act out incredibly detailed scenarios with their bodies, using the pantomime to communicate with humans and other apes, according to a new study.
The study, published in the latest Royal Society Biology Letters, adds to the growing body of evidence that orangutan mini charade-like displays feature characteristics of language and reveal just how creative, intelligent and manipulative these great apes can be.
Orangutans "show abilities that are considered by some to be important in the evolution of language and that, to this point, have been considered uniquely human," co-author Anne Russon told Discovery News.
"Of course what orangutans do isn't up to Marcel Marceau, but they can certainly fake their own bodily signals, the essence of pantomime, and that opens up a much richer world of communication than we have believed possible," added Russon, a Glendon College professor of psychology.
Russon and colleague Kristin Andrews identified pantomime cases by mining 20 years of text and video data from observational studies conducted on orangutans. Most of the orangutans were rescued from the illegal pet wildlife trade and were sent to rehabilitation programs so they could resume life in the forests of Indonesian Borneo.
"Pantomime, like language, can be used to declare, lie, request, reminisce, tell stories, teach, explain and more," Andrews told Discovery News. "We saw cases of pantomime used to request and to deceive, which are typical examples of great ape communication but, interestingly, we also report one case of pantomime used to tell a story, to reminisce and to make a statement."
For that case, an older orangutan female named Kikan reenacted how a human worker helped to heal Kikan's wounded foot. Beforehand, the person noticed that Kikan had accidentally pierced the sole of her foot with a small stone, so the worker used a pencil to pick the stone out and then dripped latex from the stem of a fig leaf into the wound. Such latex is locally known to help dry wounds.
Kikan watched all of this intently and resumed playing when the treatment finished.
Over a week later, Kikan hugged the human healer's leg. The worker was busy observing another orangutan and didn't pay much attention. Kikan returned with a leaf and completely reenacted the leaf treatment that had been given to her foot. Three months later, Kikan held up her now-healed foot to the person.
During yet another instance of pantomiming, an adolescent female orangutan named Siti made a half-hearted attempt to open a coconut with a large stick. The researchers jokingly call this sort of behavior "poor me," referring to how the crafty apes feign weakness to get others to help.
When Siti "failed," she handed the coconut to a human staff member, along with the stick. She then pretended to use the stick as a machete, reenacting how she'd seen this person opening coconuts with machetes. He got the picture and opened the coconut with a machete while Siti impatiently waited with arms folded.
"Pantomimes often occur as elaborations on failed messages," explained Russon. "My guess is that messages more often fail when orangutans address them to human versus orangutan partners, because humans are less adept at reading the messages properly."
But the orangutans pantomimed amongst just themselves too, communicating things such as "scratch me with this stick," "eat this fruit," and "wipe your dirty face off with this leaf."
"I think these are exciting findings that help corroborate other observations of iconic or pantomimic gesture in great apes, some of which have been doubted as being such only 'in the eyes of the observer,'" said Joanne Tanner, a leading expert on gorilla gestural communication who works with the Gorilla Foundation.
Prior research indicates that gorillas, chimpanzees and bonobos can also pantomime.