Chimpanzees looking for fruits in the treetops © Ammie Kalan
If you see trees with ripe apples in the autumn, you know: now it is worthwhile to stop by the grapevines, because many types of wine and apple are ripe at the same time. Similar conclusions seem to come from our closest relatives in the animal kingdom, the chimpanzees. This could show German researchers by observations in the Taï National Park of West African Côte d'Ivoire. It was already known that chimpanzees use their spatial memory to find plants with fruit. However, why they go to these sources of food at very specific times, was previously unclear. To investigate this question, the researchers around Karline Janmaat and Christophe Boesch from the Max Planck Institute for Evolutionary Anthropology in Leipzig have closely watched wild chimpanzees foraging for food. Above all, they recorded the scrutiny of the animals in the treetops when they were looking for fruit. Particularly interesting for the researchers were situations in which the monkeys systematically searched the treetops, although they did not bear any ripe fruit. The animals had expected to see something, the researchers concluded.

The scientists could rule out that the investigative staring into the treetops was triggered by the sight or smell of fruit. Rather, the analysis of the footage suggested that the chimpanzees control these trees in anticipation of finding fruits for consumption there in the near future. According to the researchers, the animals know that some tree species bear fruit at the same time and use this botanical knowledge in their daily foraging. So when the fruits of a particular tree are ripe, chimpanzees inspect other tree species carefully to see if they are already bearing fruit.

Researchers can predict which trees will visit the animals

The chimpanzees base their expectations on a combination of two abilities, the researchers explain: They can distinguish tree species and assign seasonal Eastern varieties. "The chimpanzees do not just develop a fondness for a particular fruit that they often ate in the past, " says Karline Janmaat. "We can predict which trees the animals will inspect based on the simultaneous fruit production of certain tree species." Display

The discovery also sheds light on human development history, the researchers say: "Our results show the variety of strategies our next relatives, the chimpanzees, have developed in foraging. This also highlights the evolutionary origins of the human capacity for categorization and abstract thinking, "says co-author Christophe Boesch, head of the Department of Primatology at the Max Planck Institute for Evolutionary Anthropology.

Karline Janmaat and Christophe Boesch (Max Planck Institute for Evolutionary Anthropology in Leipzig) et al .: Animal Cognition, April 10, 2013 © wissenschaft.de - Martin Vieweg

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