Twice the team saw the bonobos capture, kill, and eat their monkey prey.
"The second I read this, I thought: Oh good, finally!" said primatologist Elizabeth Lonsdorf of the Lincoln Park Zoo in Chicago.
"Bonobos being so peaceful never sat well with me," said Lonsdorf, who was not involved with the study.
"We see all species of captive apes, including bonobos, hunting animals, like squirrels, that wander into their enclosures. I was just waiting for something like this to come up," she said.
Primatologist Frans de Waal at Emory University in Atlanta said the research "changes our perception of bonobo social organization."
"This is a milestone finding," said de Waal, who also was not involved with the study.
"Now that actual observations have been made, [it] changes our perception of bonobo social organization," he said.
The scientists, funded in part by the National Geographic Society's Committee for Research and Exploration, were intrigued to find that some female bonobos hunt just as well as the males. (The National Geographic Society owns National Geographic News.)
Among chimpanzees, females rarely hunt and have not been seen taking active roles in hunting parties.
But female bonobos launched themselves up trees and attacked their monkey prey just as effectively as the males, Hohmann and Surbeck reported.
"That females are hunting at all came as a surprise, but a few of them are truly excellent hunters," Hohmann said. "We just did not expect that."
Previous studies have found bonobo communities to engage amicably with monkeys they meet.
Bonobos have been observed "borrowing" baby black-and-white colobus monkeys and playing with them as if they were toys. They have also been seen engaging in grooming behavior with red colobus monkeys.
The Chicago zoo's Lonsdorf said playmates can easily become food if conditions change.
"I've seen adult chimpanzees hunt baboon babies that their offspring were playing with just days earlier," she said. "The same could easily be true of bonobos."
Emory University's de Waal said, "We are seeing in bonobos what happened a few decades ago for chimpanzees: field studies begin to report great variation from population to population."
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