Throughout West Africa’s Taï National Park, the miniature mangabey monkey scavenges on the remnants of hard nuts that have been cracked open by larger animals, such as chimpanzees and hogs.

Curious researchers wanted to learn more about this eccentric behavior, so they analyzed camera trap data collected in four significant regions of the park to do so. Their findings appear in the American Journal of Primatology.

Image Credit: Tai Chimpanzee Project, Alexander Mielke

The camera trap data presented the researchers with 190 unique incidents of nut-cracking, and in many of those, mangabey monkeys and various foul and squirrels responded positively to the nut remnants.

Albeit uncommon, the larger chimpanzees sometimes prey upon the smaller mangabey monkeys. Unsurprisingly, the mangabey monkeys displayed boosted alertness to their surroundings, indicating their awareness of the potential threats imposed by visiting a predator’s previous feeding grounds.

"After studying both species for many months, I remain intrigued by the puzzling relationship between mangabey monkeys and chimpanzees," said study co-author Karline Janmaat of the University of Amsterdam and the Max Planck Institute of Evolutionary Anthropology.

"At some moments the monkeys seem to be scared of these potential though infrequent predators, while at other times they approach chimpanzees within meters to profit from their tool-using skills as if they had learned to anticipate the other species 'mood'."

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Surprisingly enough, mangabey monkeys were the most frequent visitors of the nut remnants despite their relationship to chimpanzees on the food chain. The findings are perplexing and seem to raise more questions than answers.

"The decisions of mangabeys to approach food left-overs from potential predators may imply contextual knowledge that helps the monkeys to judge when they are safe and when they need to be vigilant or move into a safe position," Janmaat added.

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Mangabey monkeys can’t open the nuts for themselves because they aren’t strong enough. That said, the findings appear to highlight an unusual bond between predator and prey that is both interesting and perplexing at the same time.

Source: University of Amsterdam