Island monkeys do not recognize big cat calls

Monkeys living on an island without big cat predators do not show any particular alarm when recorded tiger growls are played to them, according to research by a UC Davis graduate student. The pig-tailed langurs do, however, flee in a hurry from the sound of human voices.

"This contributes to a growing literature on how animal behavior changes under relaxed selection pressures," said Jessica Yorzinski, a graduate student in animal behavior at UC Davis, who authored the study with Thomas Ziegler of the German Primate Center in Göttingen, Germany.

Pig-tailed langurs are medium-sized monkeys that spend most of their day sitting in trees in small groups eating leaves. Their close relatives on the mainland of Indonesia are prey for tigers and leopards, but on the Mentawai islands, the monkeys have been isolated from big cats for about half a million years.

Yorzinski played recordings of tiger and leopard calls and growls, as well as the sounds of elephants (another animal unknown to the monkeys), pigs and birds (animals they know, but which do not eat monkeys) and people talking in the local language. People do hunt the monkeys for food.

On hearing the noises, the monkeys would look around and at each other and might leave the area. They did not show any greater alarm at hearing big cat noises than at hearing an elephant, and would flee in about four to five seconds. But on hearing recorded human voices, the monkeys would flee within a second. They did not flee from bird or pig noises.

Yorzinski, of course, had to take care to stay out of sight when locating monkeys and setting up speakers. "We couldn't do the experiment if the monkeys saw us first," she said.

Source: University of California - Davis

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Citation: Island monkeys do not recognize big cat calls (2008, January 17) retrieved 25 June 2019 from
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Jan 17, 2008
What is the actual finding of this study? I have to be missing something. It appears that, not surprisingly, a new noise that has never been heard before didn't affect the monkeys and they were unaware of possible danger associated with the completely foreign noise. I don't see where it matters if the noise was recorded from a big cat or an equally emotional Star Wars sound effect - it was unknown to the local population. Oh, and the people aspect. Of course monkeys run away from people. Why wouldn't they? Soem people do things to animals. And if the local population has learned that pigs don't harm them, why would they run away? I don't get how this warrented publication and how it is anything beyond common knowledge.

Mar 17, 2008
Ratings should be based on contributions to the discussion, not whether one agrees or not. I did not find the tone of your response conducive to discussion, nor did I find your low rating of my comments as helpful. I would enjoy a good debate/discussion, but you opened with a rating of '1' on my comment, and then concluded with a flury of generalizations about my intelligence and knowledge. Again, I would (and frequently do) enjoy engaging in further discussions on topics such as this where there is legitimate disagreement.

Mar 27, 2008
OK, if you have calmed down: I state that it doesn't require a trip to the Mentawai islands to observe this behaviour. They went there to insure some isolation of the population. They could have used alley cats from downtown Berlin. They, too, haven't heard big cat calls, nor are hunted by humans for food. I think the results are more intuitive than insightful. Sometimes it helps to confirm hypothesis (know what you know) but in this case, the whole study and report seems shallow. I again don't see what the purpose of this study is. A free trip to the islands, perhaps?

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