Chimps’ prodigious memories for fruit trees revealed
Clever chimpanzees memorise the precise locations of their favourite fruit trees amid forests of thousands of similar trees and even remember when each tree is most likely to be in season, new research has shown.
Primatologists studying the apes in the Ivory Coast’s Tai National Park used GPS to map the locations of more than 12,000 trees and identified 17 types of fruit-bearing types.
Not only would the chimps ignore the most abundant fruit trees in favour of their favourites but they were able to walk directly to them. Chimps who had been separated for days would even appear to use popular trees as meeting points, Emmanuelle Normand of the Max Planck Institute in Germany said.
“We were amazed by the apparent easiness by which chimpanzees discover highly productive fruit trees. Or how after being separated from other group members for hours or days, they could join each other silently at a large fruit tree, like if they would have had an appointment at this place,” Normand told the BBC.
The study revealed that chimpanzees visited the same trees far more than would be expected if the apes’ choice was dependent on chance, returning to the same tree on average once in about five-and-a-half days.
As well as targeting their favourite fruits, the chimps seemed to know when each tree would be in season, often ignoring nearby trees in favour of more distant – but also more bounteous – ones.
“Across all seasons, it seems that they have preferred tree species,” said Normand. “Like when it is the coula nuts season, chimpanzees crack nuts using tools for hours during a day . Or when it is the Sacoglottis fruits season, then the chimpanzees stay hours digging their fruit wadge in the water to press a maximum of juice from those fruits.”
Primatologists believe the development of the ability to recall the location of particular fruit trees and navigate to them in search of food could have been a key stage in the development of more sophisticated primate brains.