In the Footsteps of the Elusive Grauer’s Gorilla

Unlike their mountain gorilla cousins, only a few of the critically endangered Grauer’s gorillas of the Democratic Republic of the Congo have been habituated to human presence. These habituated populations, all of which live in highland habitats, have been periodically studied since the 1970s, so most of what we know about the ecology and behavior of Grauer’s gorillas comes from highland populations despite the fact that the majority of Grauer’s gorillas live in lowland forests. That all changed recently, when scientists at the Dian Fossey Gorilla Fund published two separate papers in the journal Folia Primatologica on research into the movement and feeding patterns of the elusive Grauer’s gorillas that live in the lowland part of the habitat.

Critically endangered Grauer’s gorillas have declined in population by 80% over the past 25 years.

In 2011, the Fossey Fund began field work in an area of lowland forest located between the two major national parks of the eastern DRC. This 1,300 square kilometer area, now an officially recognized community forest known as the Nkuba Conservation Area (NCA), is home to at least 200 Grauer’s gorillas.

As work was being done to create this protected community forest, Fossey Fund scientists saw an opportunity to set up several long-term research projects that would allow them to collect information on the area’s gorillas for the first time. Dr. Yntze van der Hoek calls this research into the unhabituated gorillas of the lowland rainforests, about which little was known up until now, “unique.” And, he says, “while our work quickly yielded data for initial genetic studies, it took many additional years of following gorillas from nest to nest to lead to the first description of the diet and the daily travel distances of Grauer’s in lowland forests.”

The Fossey Fund team found that Grauer’s gorillas in the NCA eat plant stems, leaves, pith, bark and roots, as well as several kinds of fruit, ants, termites and fungi. They also uncovered a large variation in daily movements, with the gorillas moving relatively far in months when fruit consumption is high. In both diet and travel distances, these Grauer’s differ from their habituated relatives in highland habitats. Instead, their ecology resembles much more that of western lowland gorillas, found in other parts of central Africa.

Urbain Ngobobo, country director of Dian Fossey Gorilla Fund in DR Congo, who was part of this research effort since its beginning, says he is “pleased to see we are now reaching the stage where we can draw conclusions from all the hard work. This new knowledge on Grauer’s from lowland environments changes the way we view the ecological role of Grauer’s gorillas, and allows us to better understand and protect this highly threatened animal.”

Unhabituated group of Grauer’s gorillas in the forest in Nkuba Conservation Area captured by camera trap.