Gorillas are digging for a surprising food in the jungle soil

In the dense rainforests of the Republic of Congo, western lowland gorillas are often seen foraging through the soil. They were long assumed to be foraging for insects, but recent research has turned this assumption on its head.

The real prize hidden in the dirt is not insects at all, but deer truffles – specifically, a species known as Elaphomyces labyrinthinus.

This revelation not only reshapes our understanding of gorilla behavior, but also highlights the deep value of traditional ecological knowledge. The research, from the Nouabalé-Ndoki National Park, reveals how primates are deeply connected to their forest environment.

Discovery of truffle-eating gorillas

The study was led by Gaston Abea, a member of the semi-nomadic Bangombe people and the first Indigenous person in Ndoki to become the lead author of a peer-reviewed scientific paper.

Born in the village of Bomassa, Abea brought together deep cultural understanding, sharp observational skills, and modern scientific methods to uncover the truth behind soil-scratching gorillas.

Abea spent over a decade working at the Mondika and Goualougo field stations, tracking gorilla behavior. His local tracker background gave him a unique perspective, helping him spot patterns others might miss.

“My people’s traditional knowledge of these forests is endangered by modern lifestyles but is proving invaluable in continuing to study and preserve these ecosystems,” said Abea.

His work strengthens the growing recognition of Indigenous perspectives in conservation, though academic research still often overlooks them.

Truffle digging is a regular behavior

To understand this behavior, the researchers conducted daily observations of four different gorilla groups across two sites: the Goualougo Triangle and the Djéké Triangle. They observed these groups nearly every day for almost ten years, documenting each instance of soil scratching.

The team also used molecular classification tools to identify the truffles being foraged. They conducted group scans to determine how much time gorillas spent searching for truffles.

Then, the researchers used video observations to measure how efficient the animals were during these foraging bouts. Over time, the pattern became clear: soil scratching was a consistent strategy to find deer truffles, not an aimless search or an insect hunt.

Some gorillas dig more than others

Interestingly, not all gorilla groups embraced this behavior equally. Soil scratching was most frequent in Buka’s group, followed by Kingo’s and Mététélé’s groups.

In contrast, the Loya-Makassa group rarely engaged in truffle foraging. The behavior’s distribution seems tied partly to the availability of truffles, but not entirely.

Social factors appear to influence the practice as well. In one striking example, an adult female gorilla moved from a group that rarely scratched soil to one that did so almost daily. She soon began to mirror the habits of her new group, suggesting that cultural transmission may shape how gorillas forage.

“This is an exciting finding for our understanding of gorilla foraging behavior,” said David Morgan of the Lincoln Park Zoo, who worked on the study and has spent years researching in Ndoki.

Gorillas carefully select truffles

One of the most vivid pieces of evidence came from a gorilla named Jeanne. Photographed in the Goualougo Triangle, Jeanne was seen scraping away forest leaf litter with her hands.

Once the gorilla exposed the soil, she pinched her fingers together and brought a small round object – presumably a truffle – to her mouth. This precise motion defined a successful foraging attempt and offered a glimpse into just how deliberate the behavior is.

The study’s inclusion in a special issue of the journal Primates marked a milestone. The issue celebrated 25 years of research in the Ndoki forest and brought attention to behaviors that may have otherwise gone unnoticed.

Protecting truffle-foraging traditions

Abea’s findings were incorporated into an ecological impact assessment for the Djéké Triangle.

As a result, conservation managers decided to adjust planned locations for tourism-related infrastructure. The aim was to protect areas where truffle foraging occurs regularly, ensuring this unique behavior could continue undisturbed.

“This is Gaston’s first article as lead author – a milestone for his career and for our capacity-building efforts,” said Morgan. “He is the first research assistant of Indigenous People’s origin to become first author, in the Ndoki landscape.”

The decision to shift construction plans also highlights a growing understanding of cultural behavior in wildlife. These are not just instinctive acts but socially-influenced practices that may vary by group and change with experience.

From gorilla hunters to guardians

Abea’s story represents more than scientific achievement. It also reflects a cultural shift within his own community. He is one of over 100 Congolese research assistants trained since 2005 at Ndoki, many of whom come from nearby villages and Indigenous Ba’Aka communities.

“Our ancestors used to hunt gorillas, now we protect them, and I hope to inspire other Ba’Akas to do the same,” said Abea.

His journey, from a boy in Bomassa to lead author of a major scientific article, mirrors the broader transformation in conservation thinking – one that values the voices and wisdom of local communities.

Local insights shape global research

While the knowledge about gorillas and foraging for truffles is slowly gaining recognition in the sciences, it still appears too rarely in published research. This study shows how blending local knowledge with science can reveal key insights into animal behavior and ecosystem health.

“This paper shows how much traditional ecological knowledge, scientific research, and conservation can benefit from each other,” said Dr. Sydney Ndolo, second author of the paper and now professor of Botany at Université Marien Ngouabi in Brazzaville.

“Local cultures will only survive if they are properly valued, and research is an important means of achieving this.”

Through Abea’s work and this study, a hidden part of gorilla life now comes into view – one shaped by truffles, food, forest, and social bonds. And alongside it, the role of Indigenous knowledge in science gains new ground.

The study is published in the journal Primates.

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