Chimpanzees use different types of memory to find insects hidden underground, study shows

Next to humans, chimpanzees are the animals with the most complex memories. They remember where and when ripe fruit is available and use this information to decide which trees to visit and even where to sleep in order to eat that fruit first thing in the morning. However, the cognitive strategies they use to find foods of animal rather than plant origin are not yet well understood.

Now experts at the University of Barcelona and the Jane Goodall Institute Spain have conducted a study that describes the previously unknown cognitive abilities that wild chimpanzees in Africa use to eat army ants hiding in hard-to-locate underground nests. This is the first work to describe how these primates use spatial and episodic memory to extract social insects from nests hidden underground.

The study shows for the first time how chimpanzees can successfully overcome the cognitive challenge of using an animal food source in the wild for years.

The results, published in the journal Communication biologyexpand our understanding of the cognitive strategies of non-human primates and provide new insights for reconstructing the development of cognitive abilities in our lineage.

Army ants (Dorylus spp.), also known as the fearsome Marabunta, form the largest colonies of social insects on the planet. These hymenopteran insects are rich in proteins and minerals – important nutrients for chimpanzees – but are very difficult to find because they nest under rocks, roots and fallen vegetation and move unpredictably.

As part of the study, the team analyzed a total of 679 chimpanzee visits to four army ant nests that occurred between 2018 and 2022 in the Dindefelo Nature Reserve, a savanna habitat in southeastern Senegal.

Andreu Sánchez-Megías, Ph.D. student and lead author of the paper says: “We examined whether chimpanzees intentionally return to nests, the strategies they use to detect the presence of ants, the availability of these insects, and the extent to which chimpanzees eat them.”

He notes that the ant nests are “rare and almost always invisible, and so memorizing the exact location of the nest is a good foraging strategy for the chimpanzees. The nests are abandoned and reoccupied at irregular intervals, and this is a key component.” “The behavior of the ants allows chimpanzees to repeatedly visit the same nests to feed on these insects.”

See, smell, taste and touch

It appears that these monkeys remembered previous visits to ant nests and changed their behavior depending on whether they had encountered the insects on previous visits. The results suggest that chimpanzees use spatial memory to remember the exact location of hidden ant nests and episodic memory to remember whether they found ants on previous visits to the same nests.

Episodic memory is the ability to remember where, when, and what happened in previous experiences and is named after episodic memory in humans, which consists of the same abilities as well as the ability to verbalize memories. Because nonhuman animals cannot explicitly tell us what they remember, this ability, which corresponds to human episodic memory, is called episodic memory.

Additionally, it is notable that this is the first study to describe how chimpanzees use four senses (sight, smell, taste and touch) to inspect empty nests and determine whether ants are present.

Importance for nature conservation and for understanding human evolution

Serra Hunter Professor R. Adriana Hernandez-Aguilar says: “It is important to emphasize that studying chimpanzee cognition in an ecologically relevant context – such as the savannah in which our research was conducted – leads to a better understanding of the development of chimpanzees “contributes to human cognitive abilities.” , since the first hominins inhabited similarly dry, open and hot landscapes.”

“Chimpanzees are an endangered species, and learning more about the strategies they use to obtain important foods in the wild will help us conserve them,” the researchers conclude.