Barbara J. King

Friday Animal Blog

Chimpanzee Pant Grunts

August 6, 2010

A new study published online at Animal Behaviour by primatologists Marion Laporte and Klaus Zuberbuhler at the University of St. Andrews shows us how much we still can learn about chimpanzee behavior, even in this 50th-anniversary year of Jane Goodall’s research. Focusing on communication, Laporte and Zuberbuhler studied the pant-grunt, a vocalization that is given only by low-ranking chimpanzees to higher-ranking ones.

The pant-grunt is an unusual primate vocalization because, instead of being broadcast generally as are alarm calls or food grunts, it’s directed by one animal to a specific receiver. Working in the Budongo National Park in Uganda, Laporte and Zuberbuhler wanted to find out how female chimpanzees used their pant hoots. Are the pant-hunts, as if often claimed for primate vocalizations, fixed and inflexible signals? “If pant-grunts merely functioned as a ritualized signal of subordination,” they reasoned, “call production should be determined by the relative rank of the receiver, regardless of other social factors, such as the composition of the nearby audience, or the nature of the ongoing social interaction.”

Because of the research I did for my book on ape communication, The Dynamic Dance (published by Harvard University Press in 2004), I immediately thought that of course ongoing social interaction would affect call production! Apes, with their propensity for emotional bonding, are incredibly sensitive to what’s going on around them, a fact I’ve noted over and over again in my observations of captive bonobo and gorilla families.

And the new Budongo data do support a notion that apes are acutely attuned to the companions around them. Nine females were studied for 455 hours (though for some findings, data are based on fewer than nine females.) Although, as expected, pant-grunts were directed up the hierarchy, it wasn’t the case that females pant-grunted whenever they met up with a higher-up.

Instead, females pant-grunted:

*More to the alpha male than expected. Yet overall there was no correlation between male rank and males’ receiving pant grunts.

*Less to other dominant apes when the alpha male was around, and less also (although in a weaker effect) when the alpha female was around.

*More during friendly interactions than in aggressive ones.

Social status of nearby animals can thus alter the pant-grunting behavior of chimpanzees. But let’s turn this wording around and give female chimpanzees their due: Female chimpanzees shape their own surroundings when they pant grunt!

It’s interesting to note that this community’s alpha male was observed to be quite violent with other group members. Perhaps a high rate of pant-grunting appeased him—yet overall, the level of threats did not explain female pant-grunting . Certainly, it’s the case that in chimpanzee society, any male is higher-ranked than even the highest-ranked female. Because of this situation, females need to take advantage of opportunities to shape what happens to them. The researchers point out that females’ greeting of other apes in the presence of the alpha sometimes triggered his aggression, a response that may help explain the reduced levels of pant-grunting near the alpha.

Laporte and Zuberbuhler say that their data offer evidence “that the presence and identity of bystanders had a significant impact on an individual’s willingness to produce a vocal signal.”

I love the next part of their conclusion, because it fits so perfectly with a view of chimpanzees as thinking, feeling creatures: “Pant grunting is part of a chimpanzee’s tool kit to build social relations, rather than a straightforward consequence of a social hierarchy.”

Pant-grunts, then, are not calls uttered automatically when one chimpanzee sees another of higher status. Instead, they represent yet another way – in addition to making and using organic and stone tools, hunting monkeys cooperatively for food, acting with compassion to help a companion, and yes, even killing other chimpanzee competitors on occasion-- that chimpanzees strategically shape the course of their own lives.

Comments

  1. October 15, 2010 7:16 PM EDT
    This is fascinating - is there a web source for recordings of primate vocalizations? I think I know what a pant-grunt is, but not sure if the authors' are referring to the same vocalization.
    - Melanie

Selected Works

Nonfiction
Why are animals so irresistible to us? Why do we live with and care so deeply about them? From the famous "art caves" of ice-age Europe, to the ancient villages where animals were first domesticated, to stories of apes, whales, dogs, and cats doing fascinating things today, King weaves together a scenario about the animal-human bond that encompasses our past, present and future.
Can scientists discover a prehistory of religion just as they have traced the evolution of technology, language, and art? What does compassion in chimpanzees, or burial patterns in our human ancestors and Neanderthals, tell us about the origins of religion? In Evolving God, named a Top Ten Religion Book for 2007 by the American Library Association, Barbara King explores these questions.
How do chimpanzees, bonobos, and gorillas-- the African apes -- communicate using body postures and gestures? Using her many years of experience studying these apes, Barbara King answers this question in a book that offers a new perspective on the evolution of language.