It's no secret that chimpanzees and a few other great apes are capable of complex language. They can be taught sign language and freely communicate with experts using body language. But what about us understanding them? A new team of researchers eavesdropping on the animals have now determined that chimps talk to one another about at least two important topics.

That's at least according to a study recently published in the journal Animal Behaviour, which details how chimp calls clearly indicate not only things like warnings (as seen in many communal species), but also the presence and whereabouts of their favorite fruits.

Ammie Kalan of the Max Plank Institute for Evolutionary Anthropology recently led a team of researchers in observing wild chimpanzees in the Ivory Coast's Taï Forest. She and her colleagues spent over 750 hours observing chimps and analyzing their calls, indentifying 379 examples of what they suspect were food calls produced for five different food species. In the course of their work, they found that higher pitched calls were produced for a single fruit species.

"Additionally, within this species, chimpanzees modified calls according to tree size, whereby smaller trees elicited higher pitched calls," the researchers wrote. "Our results suggest that chimpanzees subtly vary the acoustic structure of food calls with respect to food patch size for a putatively highly valued fruit species ."

The study even suggested that the chimps get most excited about fruit from Nauclea trees, for which the chatter was frequent.

Kalan told Discovery News that the calls essentially had a "dinner bell" effect for nearby chimps, especially in the case of calls that correlated with many Nauclea fruit.

"I never tried these fruits myself, but they do smell very good in the forest," Kalan admitted. "They are also quite big and easy to ingest, and we also know that they have a high energy content, which is important for wild animals."

The calls, she added, can even have a reunion-like effect, in which very large fruit finds, and their associated call, draw in more relatives - giving chimps an opportunity to socialize with friends they haven't seen for a while.

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