Chimpanzees Use Long-Term Memory To Forage

Lee Rannals for – Your Universe Online

Chimpanzees rely on their long-term memory when searching for food throughout the rainforest, according to a new study published in the journal Animal Behavior.

Researchers studying whether chimpanzees aim their travel to particular rainforest trees to check for fruit found that the animals use long-term memory to remember the size and location of fruit trees and feeding experiences from previous seasons.

The team recorded the behavior of five chimpanzee females for continuous periods of four to eight weeks throughout multiple fruiting seasons in the Taï National Park, Côte d’Ivoire. The research period lasted for a total of 275 complete days. They also analyzed nearly 16,000 potential food trees with different crown sizes that were actually approached by the chimpanzees.

The scientists found that the animals fed on significantly larger trees than on other reproductively mature trees of the same species, especially if their fruits emitted an obvious smell.

Chimpanzees in the study checked most trees along the way during travel, but 13 percent were approached in a goal-directed manner. These target approaches were not initiated by visual cues and they occurred more often when females foraged alone and when trees were large.

Researchers determined that the chimpanzees were being guided by long-term memory of the location of large potential food trees. One observation in particular showed a chimpanzee was able to remember feeding experiences across fruiting seasons. The team said that long-term phenological data on individual trees indicated that the interval between successive fruiting seasons and the “memory window” of chimpanzees required for effective monitoring activities varied from two months to three years.

“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”, said Karline Janmaat from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology added that for a long time, people claimed that animals cannot remember the past. However, the researchers’ work shows this just isn’t true.

“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,” Boesch concluded.