Sukari the gorilla can grunt. She can sing. She can growl. Now, as scientists report, gorillas have a new way to express themselves. Sukari knows how to “grunt”.
She and the other gorillas at the zoo make a noise, a cross between a sneeze and a cough, when food keepers are nearby. The unusual expression, which has not been observed in the wild and never before described in the species, may help gorillas attract people’s attention, says primatologist Roberta Salmi of the University of Georgia in Athens. Snow adds to a small but growing pile of evidence for this captive apes can produce novel vocal soundsSalmi and her colleagues report on August 10 in PLANE ONE.
Salmi first encountered Snow years ago at Zoo Atlanta, when she and a keeper noticed that the gorillas were making strange noises. “We really laughed,” she recalls. Gorillas make all kinds of screams, but the snow stood out. When the animals exhale this noise, they open their mouths wide, as if preparing to yodel. “It’s very theatrical,” Salmi says. And it appeared, it seems, only in a specific situation – when guards appeared with food.
Salmi and her colleagues wondered if the animals also coughed at other times. So they recorded eight western lowland gorillas at Zoo Atlanta in three different scenarios: when a bucket of fresh grapes, a keeper, or a keeper holding the grapes sat outside the enclosure. The team found that the gorillas farted most often when both the keeper and the food were sitting next to each other. And they made other sounds that might attract a person’s attention, like clapping, beating their chests, or banging their hulls. When the gorillas saw only the grapes or just the keeper, they were mostly silent.
“It’s quite a decent indication of the animals’ intention to demand something from the keeper,” says Zanna Clay, a primatologist at the University of Durham in England, who was not involved in the work.
And snoring wasn’t limited to the gorillas at Zoo Atlanta. Surveys conducted at 19 zoos in the United States and Canada found that other gorillas make the same snoring sound. Salmi says these animals probably didn’t learn to cough from Zoo Atlanta gorillas because they never came into contact with each other.
At this point, her team can only guess where the sniffles came from, though she notes that a sneezing cough can be particularly good at attracting a keeper’s attention. “Coughing and sneezing are signs of a cold that caregivers pay special attention to,” she says.
If gorillas want something they can’t physically reach, they may be “trying to use communication signals to manipulate people” into helping, says Jared Tagliatella, an evolutionary biologist at Kennesaw State University in Georgia, who was not involved in the study.
To date, most research into the vocal repertoire of great apes has been limited to their charismatic gorilla cousins. Captive chimpanzees can blow “raspberries” and orangutans can whistle, but gorilla cries are not as well studied. “There is a small gap in our understanding,” says Tagliatella. If chimpanzees, orangutans and now gorillas can produce new vocalizations, an ability that is present in humans but rare in the animal kingdom, perhaps an ancestor of these animals and humans did the same, he says.
Clay believes that studying gorillas may provide new clues about what drives the development of language. She points out that snoring isn’t the same as speaking, but it can be a sign that there’s more to a gorilla than meets the eye.