Chimps' Feeding Habits Suggests Long-Term Memory Use
A study of chimpanzees in the forests of Taï National Park in Côte d'Ivoire, suggests that the apes are able to use long-term memory to relocate rich food sources they encountered in previous seasons.
Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, found that chimps recall the size and location of fruit trees and also remember feeding experiences from previous visits to the trees using a memory window which can be two months to three years old.
Research leader Karline Janmaat and her colleagues studied the behavior of five female chimpanzees for periods of four to eight weeks for a total study time of 275 days.
Janmaat and her team found the chimps were more likely to seek out large, fruit-bearing trees, especially if their fruits emitted an obvious smell. But size was not the only consideration. Larger trees that did not bear fruit were quickly overlooked by the chimps.
As the chimps explored for food, they checked most trees along their route, but 13 percent of the time, the researchers observed goal-directed behavior in the chimps, which suggested they remembered from previous experience that the trees they were traveling to were good sources of food.
One chimp, which the researchers tracked over three summers, repeatedly sought out the trees she fed on in previous seasons, which the researchers suggests is indicative of long-term memory.
"The present study on chimpanzees is the first to show that our close relatives use long-term memory during their search for newly produced tropical fruit, and remember feeding experiences long after trees have been emptied," Janmaat said.
Christophe Boesch, another Max Planck researcher, said: "For a long time people claimed that animals, contrary to humans, cannot remember the past. This study helps us to understand why chimpanzees and other primates should remember events over long periods in time. And guess what? It also shows they do!"
The researchers' work is published in the journal Animal Behavior.