The study reveals for the first time how chimpanzees can successfully meet a cognitive challenge to exploit an animal food source in the wild for years.
The findings, published in the journal Communications Biology, expand our understanding of the cognitive strategies of non-human primates, and provide new insights for reconstructing the evolution of cognitive abilities in our lineage.
The study is led by the experts Andreu Sánchez-Megías and R. Adriana Hernandez-Aguilar, from the UB’s Faculty of Psychology and the Jane Goodall Institute Spain. Other participants are Laia Dotras, from the same faculty and institute; Jordi Galbany, also from the same faculty and institute, and the UB Institute of Neurosciences (UBneuro); Adrián Arroyo, from the Seminar on Prehistoric Studies and Research (SERP), the UB Institute of Archaeology (IAUB) and the Catalan Institute of Human Palaeoecology and Social Evolution (IPHES-CERCA). Carlota F. Galán, Nadia Mirghani, Manuel Llana and Justinn Renelies-Hamilton from the Jane Goodall Institute Spain also participated in the study.
Remembering over the years where the hidden nests of army ants are
Army ants (Dorylus spp.), also known as the fearsome marabunta, form the largest colonies of social insects on the planet. These hymenopterous insects are rich in protein and minerals — key 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 analysed a total of 679 chimpanzee visits to four army ant nests that occurred from 2018 to 2022 in the Dindefelo community nature reserve, a savannah habitat in the south-east of Senegal.
Andreu Sánchez-Megías, PhD student and first author of the article, explains that “we studied if chimpanzees intentionally return to nests, the strategies they use to detect if ants are present, the availability of these insects and the extent to which chimpanzees consume them”. He notes that the ant nests “are scarce and nearly always impossible to see, and thus, for the chimpanzees, remembering the exact location of the nest is a good foraging strategy. The nests are abandoned and reoccupied at irregular intervals, and this key component of the ants’ behaviour allows chimpanzees to repeatedly visit the same nests to feed on these insects”.
Sight, smell, taste and touch
It seems that these apes remembered previous visits to ant nests and modified their behaviour depending on whether they had encountered the insects on previous visits. The findings indicate that chimpanzees use spatial memory to remember the exact location of hidden ant nests, and episodic-like memory to remember whether they found ants on previous visits to the same nests.
Episodic-like memory is the ability to remember where, when and what happened in past experiences, and is named after episodic memory in humans, which consists of the same abilities plus the ability to verbalize memories. Because non-human animals cannot explicitly communicate to us what they remember, this ability equivalent to human episodic memory is called episodic-like memory.
Furthermore, it is noteworthy that this is the first study to describe how chimpanzees use four senses (sight, smell, taste and touch) to inspect empty nests and detect if there are ants.
Importance for conservation and for understanding human evolution
Serra Hunter professor R. Adriana Hernandez-Aguilar stresses that “it is important to emphasize that the study of chimpanzee cognition in an ecologically relevant context — such as the savannah where our research was carried out — contributes to better understanding the evolution of human cognitive capacities, given that the first hominins inhabited similarly dry, open, and hot landscapes”.
Furthermore, “chimpanzees are an endangered species and learning more about the strategies they use to obtain important foods in the wild helps us to conserve them”, the researchers conclude.
