December 31, 2011

Researchers Find Chimps Selective When Giving Warning Calls

Chimpanzees might be able to determine whether or not their fellow chimps need to hear a specific message, according to a new study published in the journal Current Biology.

According to Guardian Science Correspondent Ian Sample, researchers from the University of St. Andrews, the Max Planck Institute for Evolutionary Anthropology, and the Budongo Conservation Field Station in Uganda, observed the creatures selectively sounding a warning call, apparently based on whether or not they believed that their audience was aware of the danger.

In order to observe how the chimpanzees communicated with each other about potential dangers, the researchers placed plastic rhino and gaboon vipers into the paths of the 33 wild chimpanzees. They then observed the animals reactions to them, BBC News Science Reporter Victoria Gill said on Friday.

"These [snake species] are well camouflaged and they have a deadly bite," lead researcher Dr. Catherine Crockford, of the University of St Andrews, told Gill. "They also tend to sit in one place for weeks. So if a chimp discovers a snake, it makes sense for that animal to let everyone else know where [it] is."

When the chimps saw the snake, they would leap away from it, but they would not issue a warning call, Crockford and her colleagues observed. Once they gathered themselves, they would call out with repeated "hoo" sounds, warning those who were not nearby that there was a danger ahead.

"The behavior suggests the animals knew what their fellow apes knew and made decisions over what warnings to give based on the information," Sample said of the study.

"Lots of animals give alarm calls and are more likely to do so if there's an audience, but these chimps are more likely to call if the audience doesn't know about the danger," Crockford told the Guardian.

"It's as if they're picking up on differences in ignorance and knowledge in others“¦ there's a dissociation between their emotional reaction and the vocalization," she added. "The call is not a knee jerk reaction to the snake, it's intelligent behavior."
Crockford also told reporters that they had monitored the plastic snakes all day and were well aware which animals had seen it and which had not.

She also observed that the chimps were "very focused on their audience" when they issued their warning calls, and that their research illustrates that "more of the essential ingredients needed to kickstart complex communication are evident in chimpanzees" than was previously thought.


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