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Lost in the Brouhaha: Apes’ Own Communication

Almost lost in arguments about whether and to what degree apes can learn “language” are their own native “tongues.” Each species uses a number of varied—and sometimes incredibly loud—vocal calls, as well as facial expressions and a rich body language. No researcher claims that these calls constitute a language as complex as ours. But they seem to serve the animals quite well in the wild.

Orangutans may have the most impressive individual call of any ape, the long call. It begins with a low soft grumble, modulating in pitch like a string bass player using vibrato. It builds slowly to a roar audible a mile and a quarter away through the dense Borneo jungle. The third movement falls back to a soft series of mumbles and sighs. As with many animal calls, this one announces a male, protecting his territory and possibly calling females. Some orangutans accompany this call by pulling over standing snags, creating a crash that echoes through the forest. Occasionally the crash alone is enough to trigger return long calls from neighboring males. More often, males will call back and forth to each other, presumably communicating their location and the sovereignty of their territory.

Orangutans also vocalize with grunts, grumbles and squeaks when they copulate, and young orangs squeak, bark and scream. Both adults and young make a variety of sounds with their lips and throats, sucking, burping and even grinding their teeth. Researchers have no dictionary of these sounds, or the gestures and body postures orangutans use to communicate. Because they live high in the trees of dense forest, wild orangutans have proved difficult to document.

Researchers have also studied the calls of chimpanzees. Jane Goodall and many other researchers have catalogued a wide variety of screams, grunts and so-called pant-hoots, all accompanied by striking facial expressions and body language.

Chimpanzees live in fluid social groups that change in both the short and long term. Unlike dolphins, elephants and lions, male chimpanzees form stronger and longer-lasting social bonds than do females. They cooperate in grooming and hunting, forming alliances that increase their social rank and mating success.

One of the best-studied of chimpanzee vocalizations, the pant-hoot, begins with breathy, low-pitched hoots that segue into a series of quicker, higher-pitched in-and-out pants, as if the chimp were trying to play harmonica without an instrument. Finally the pant-hoot builds to a loud climactic crescendo. Both sexes pant-hoot, and appear to do so at every opportunity where it’s appropriate to express excitement. Males and females pant-hoot differently, and even humans can discriminate between the pant-hoots of individuals with a little practice. Chimpanzees listen to distant pant-hoots and respond. These sounds may serve as identification, but they occur in such a wide variety of circumstances and with enough subtle variations that they may well carry other meanings as well.

Male chimpanzees sometimes accompany long-distance pant-hoots by drumming with their hands or feet on tree buttresses or hollow stumps or logs, and appear to use pant-hoots to communicate their location over long distances. Recent field studies tend to indicate that males keep in touch with specific individuals, primarily allies.

At least two groups of chimpanzees may speak different dialects. Well-studied groups at Gombe and Mahale pant-hoot slightly differently. Because long-distance identification of allies and rivals carries such importance for chimpanzees, dialectical differences in isolated groups makes sense. But dialects in birds, for example, arise as fledglings learn songs from their nearest neighbors. No one has yet shown that chimpanzees learn their pant-hoots from adults. Differences in habitat or in the genetic makeup of the groups could also account for the different pant-hoots.