Food-related calls have long been documented in in birds and mammals, including great apes such as chimpanzees and bonobos. To see if gorillas engaged in similar vocals, researcher Eva Maria Luef of the Max Planck Institute for Ornithology sought to create the first scientific and detailed analysis of gorilla food-associated calling. Luef and her colleagues trooped off to the Republic of the Congo to spend some time with two different populations of western lowlands gorillas, which have the easy-to-remember Linnaean subspecies designation of Gorilla. Their work, published in PLOS One, identified a fun fact about gorillas: they hum and even sing during mealtime.
The same study found that some gorillas may even sing when they’re chewing on a favorite piece of vegetation. (And you thought it was impolite to even talk with your mouth full.) Gorilla singing doesn’t approach the mellifluous stylings of, say, the Monkees, but it’s vaguely musical, and the logical thing to call this sound that clearly isn’t humming would be singing. Just as humans who perform “Aba Daba Honeymoon,” with the immortal line “Baba daba daba daba daba daba dab, said the monkey to the chimp,” are certainly singing, even if the work is “the nadir of all American expression,” according to Thomas Pynchon.
Primatologist Dian Fossey, who ᴅɪᴇd in Rwanda in 1985, noted that gorillas hum and sang. She categorized such sounds as “belch vocalizations,” which often seemed to signal contentment—can you believe some people still don’t accept that gorillas and humans have a common ancestor?
The current research, however, is the first to really track the vocalizations and connect them to specific behaviors. “And we found that it was [males—blackback adolescents and silverback adults—that] were the most frequent callers,” Luef revealed. “This is not surprising as adult males are usually the most frequent callers, concerning any gorilla vocalization. And then we found that the food calls were produced when they were feeding on certain foods. So aquatic vegetation or seeds elicited a lot of food calls. And… they never called when they were eating insects like termites or ants.” Because feasting on Formicidae or ingesting Isoptera is nothing to sing about. Even among gorillas.
Specifically, Luef and her team identified two different types of sound that gorillas in the Congo made when eating. One of them was humming – a consistent low-frequency tone akin to the “mmm” that humans make. The other was singing — random mismatched notes, like someone singing an improvised ditty. “They don’t sing the same song over and over,” said Luef. “It seems like they are composing their little food songs.”
So what’s with all the Sturm und Sang? “We believe that the food calls have a social function in gorillas,” Luef said. “They may signal to [other gorilla] listeners that an individual is busy eating at the moment. Silverback males have a special role in gorilla society…. They are most often the ones making group decisions. So when the silverback sits and eats, the others eat as well. And [when] he gets up and starts to … travel in the forest…, the others follow him. So it makes sense for the silverback to signal to his group mates that he’s still eating and then signal that he has finished eating when he stops calling.” In other words, humming and singing may be the dominant male’s Do Not Disturb sign. And his eventual silence could be gorilla for “Laᴅɪᴇs and almostmen, may I have your attention?”
In fact, Luef and her colleagues plan to do more in-depth analysis of gorilla vocalizations to see if they can learn anything about how we came to yap. They want to study “how the gorillas compose their food songs,” she said, “and whether they possess a certain repertoire of song notes, which they combine into their little food songs. That would be more similar to human language because [we have] a certain repertoire of sounds we can make, and we combine them into words and different languages. So if gorillas could do the same with their songs, that would just be amazing.” Aba daba indeed.
The vocalization seems to be a way for gorillas to express contentment with their meal, as well as for the head of the family to communicate to others that it is dinnertime. Each gorilla has its own distinct voice, and they sing louder for their favorite food.
Leuf found that while all gorillas in captivity sing while eating, in the wild, only dominant ‘silverback’ males sing, to inform the group that it’s mealtime and no one is excused. “He’s the one making the collective decisions for the group,” Luef told New Scientist. “We think he uses this vocalization to inform the others ‘OK, now we’re eating’.”