Familiarity in the Forest

For the past nine months Lincoln Park Zoo’s Dave Morgan, Ph.D., and his team of research assistants and gorilla trackers has been toiling in the Republic of Congo’s Goualougo Triangle. Their work in this remote, 100-square-mile area—nestled deep within the densely forested Nouaboule-Ndoki National Park— is delicate and at times dangerous. That’s especially true for their latest project: habituating a troop of western lowland gorillas to the presence of humans.

Lincoln Park Zoo's Curator of Primates Maureen Leahy searches for western lowland gorillas in the Republic of Congo's Goualougo Triangle

Maureen Leahy, Lincoln Park Zoo’s Curator of Primates, scans the Goualougo Triangle forest for signs of western lowland gorillas.

By getting the apes accustomed to regular monitoring, Goualougo Triangle Ape Project (GTAP) researchers can observe this endangered primate species in its native habitat and collect valuable data on the gorillas’ natural behavior and feeding ecology.

This troop of eight gorillas—comprising the silverback, a sub-adult male, two adult females, a juvenile and an infant born last October—was previously naïve to encountering humans in its wild home. For years the GTAP team had only been able to remotely monitor these gorillas, capturing rare glimpses of their whereabouts via photos taken by motion-triggered cameras. When they approached the troop, the gorillas always ran off, sometimes fleeing miles away.

The GTAP team began the slow process of habituation by searching the surrounding forest for eight to nine hours every day, looking for clues that would lead them closer to the gorilla troop. Amidst the clutter of leaf litter on the forest floor the trackers learned to hone in on folded or frayed plant stems—evidence that gorillas had been foraging in that location. They were able to identify what resembled clumps of compact dirt but were, in fact, remnants of subterranean termite mounds the gorillas had unearthed while foraging.

Dave Morgan, Ph.D., co-director of the Goualougo Triangle Ape Project, talks to Lincoln Park Zoo Curator of Primates Maureen Leahy about a termite mound that's been foraged on by western lowland gorillas.

The trackers even became experts at deciphering the age of gorilla feces defecated hours ago or days earlier.

Over time the team members were able to locate the gorilla troop on a daily basis and eventually began testing the silverback’s tolerance to their proximity. Initially, the silverback challenged their approach, displaying his dominance and forcing their retreat by aggressively charging at them. The trackers would retreat, assess the silverback’s behavior and try their approach again. Over the course of several months the silverback became more tolerant of the trackers’ proximity, allowing the GTAP team to observe his troop at a distance with which he was comfortable—approximately 15–30 feet. This is a key step in learning how this endangered species lives in the wild.

On our fourth day at the GTAP field site, Steve Ross, Ph.D., Lisa Faust, Ph.D., and I had the privilege of joining Dave and the GTAP team in the forest to learn more about the habituation process and observe the gorilla troop.

The gorilla trackers had set out in search of the troop earlier that morning, and Dave confirmed their whereabouts via text messaging using a satellite telephone. With the GPS coordinates in hand we slowly approached their location.

Dave began announcing our presence by making clucking noises, a standardized cue the trackers use to alert the gorilla troop they are approaching. “Cluck, cluck, cluck…” Dave motioned to us to approach quietly and with caution.

“There,” he said, pointing toward a thicket of vegetation. “He’s watching us.”

The GTAP team approaches the silverback leader of a western lowland gorilla troop, signaling their presence by vocalizing a series of clucking sounds.

My adrenaline at this point was through the roof. I stood there totally vulnerable without a barrier separating me from this massive adult male gorilla—a far cry from Regenstein Center for African Apes where we’re always physically separated from the gorillas. Peering through a tangle of jungle vines, there he sat: the silverback. I could see his impressive head crest and sense the apprehension in his eyes as he watched me.

Team members observe the gorilla troop’s massive silverback leader from a close distance.


Without any warning the silverback vocalized loudly while barreling toward us, stiffly postured, snapping branches along the way. I felt my heart slump into my stomach as the blur of his enormous black and gray body rushed in front of and past me, followed by his strong, pungent body odor.

When I finally regained my focus, I could see Dave, Steve and Lisa frozen alongside me, but the trackers were now several feet away. The silverback had charged right through us and separated our team into two groups! He’d clearly sent the message he was not ready to have newcomers like myself get too close to his troop. So without hesitation we retreated from the vicinity.

I had time to reflect on the exciting encounter and GTAP’s research goals during the several-hour hike back to base camp.

Very little is known about the feeding ecology of western lowland gorillas. The GTAP team’s observations of this troop’s daily and seasonal feeding habits, along with behavioral data, will play an invaluable role in the species’ conservation. Researchers might learn, for example, that certain tree species are essential food resources for these gorillas. That discovery could spur an assessment of the impact Congo’s logging industry has on this other native living treasure—western lowland gorillas—that needs to be preserved at all costs.

Hopefully, the GTAP team’s efforts will habituate others to that point of view while we still have time to act on behalf of this irreplaceable species.

Maureen Leahy

Maureen Leahy, Lincoln Park Zoo's Curator of Primates  

Maureen Leahy
Maureen is Curator of Primates at Lincoln Park Zoo where she oversees the care of 12 primate species at the Helen Brach Primate House and Regenstein Center for African Apes.


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