Chimpanzees exaggerate their screams when under attack

Oct 16, 2007

Research by the University of St Andrews shows that chimpanzees vary their screams depending on the severity of the attack and that they can exaggerate the nature of the attack, but only if higher ranking group members are in the audience. The way they scream provides nearby listeners with important cues about the nature of the attack.

The research team, comprising of Dr Katie Slocombe and Dr Klaus Zuberbuhler, found that victims' screams change in acoustic structure according to the severity of aggression experienced. Screams given in response to severe aggression (chasing or beating) are longer, higher in frequency and given in longer slower bouts than screams given to mild aggression (charges and threats).

The study, conducted with wild chimpanzees in Budongo Forest, Uganda, also shows that victims are sensitive to the composition of the audience and modify the structure of their screams accordingly. When faced with severe aggression, victims modify their screams to exaggerate the level of aggression faced, but only if there is a chimpanzee in the audience who is equal or higher ranking than the aggressor (ie a chimp capable of challenging the aggressor and helping the victim). This audience effect only occurs with severe aggression, not mild aggression, showing they only modify their calls when they most need help.

Dr Slocombe said, "We conclude victims use screams flexibly to recruit help from others and have a complex understanding of third party relations. They know exactly who can challenge who, and this knowledge of social relationships influences their vocal production. This shows there is more flexibility in their vocal communication than previously thought".

The study is published in the Proceedings of the National Academy of Sciences (Monday, October 15, 2007).

Source: University of St Andrews

Explore further: New conversion process turns biomass 'waste' into lucrative chemical products (w/ Video)

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Protections blocked, but sage grouse work goes on

12 hours ago

(AP)—U.S. wildlife officials will decide next year whether a wide-ranging Western bird species needs protections even though Congress has blocked such protections from taking effect, Interior Secretary ...

Contrasting views of kin selection assessed

14 hours ago

In an article to be published in the January issue of BioScience, two philosophers tackle one of the most divisive arguments in modern biology: the value of the theory of "kin selection."

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.