Bonobos are thriving in Salonga National Park

Scientists have finally determined the number of bonobos residing in one of the largest pristine tropical forests on Earth. This region, Salonga National Park in the Democratic Republic of the Congo (DRC), serves as a critical sanctuary for these endangered great apes.

A comprehensive study, conducted over two decades by 48 scientists, estimates that between 8,000 to 18,000 adult bonobos inhabit Salonga. While the population appears stable, researchers have noted signs of a potential decline.

Estimating the park’s bonobos population

The findings not only shed light on bonobo numbers but also identify factors essential for their survival, offering actionable steps for their conservation.

“Estimating the population of bonobos in Congo’s largest protected park is a significant step in conservation efforts,” said Mattia Bessone, first author on the study.

“We highlight the effectiveness of park rangers in preserving this endangered species, showing that Salonga’s success can serve as a model for other conservation projects.”

Africa’s largest pristine forest

Salonga National Park, Africa’s largest protected forest, spans an area equivalent to Switzerland.

Its untouched primary forest provides a haven for bonobos, a species of great ape found exclusively in the Congo.

Unlike other regions, Salonga shields bonobos from the severe threats of deforestation and commercial hunting. Despite its reputation as a stronghold, the actual number of bonobos within the park had remained unknown due to the lack of comprehensive surveys.

Revisiting bonobo data in Salonga

“There was an old number floating around of how many bonobos there were in Salonga, but this was an assumption based on surveys covering less than twenty percent of the entire park,” said Barbara Fruth, a group leader at the Max Planck Institute of Animal Behavior (MPI-AB).

Salonga’s unique research opportunity: 33,000 km² (12,741 sq miles) of protected forest and 9,000 km² (3,475 sq miles) of human settlement corridors offer vital insights into bonobo conservation.

“The unique thing about Salonga is that it is the only place where surveys have been repeated in the same areas. In this vast country, only Salonga offers the opportunity to model trends and assess whether bonobos are declining in Congo,” noted Fruth.

Compiling two decades of data

The monumental task of compiling two decades of survey data fell to Mattia Bessone, a postdoctoral researcher with Fruth.

Between 2000 and 2018, 13 surveys were conducted by a team of 48 scientists. However, varying survey methods – ranging from traditional nest counting to modern motion-triggered cameras – posed challenges.

Bessone applied statistical techniques to reconcile these differences, ensuring the data provided a clear picture of bonobo populations across the park, even in previously unstudied areas.

The resulting analysis represents the most extensive temporal comparison of bonobo populations to date, offering insights critical for conservation planning.

Bonobos in Salonga: Stable yet vulnerable

The study estimates that 8,000 to 18,000 adult bonobos inhabit Salonga, a figure aligning with past extrapolations from smaller surveys.

While the population has remained stable since 2000, the researchers noted a concerning downward trend in density and distribution. Although this trend is not statistically significant, it signals the need for vigilance.

“What this tells us is that bonobos are not in immediate danger, but we need to stay vigilant and to keep investing in conservation efforts if we are to ensure their survival,” said Bessone.

How bonobos thrive in Salonga Park

The study highlights factors that influence bonobo distribution and abundance.

Primary forest cover emerges as the main predictor of bonobo presence, while proximity to villages has a negative impact. Interestingly, bonobos are more frequently found near park ranger posts, suggesting a protective effect of law enforcement.

“We can’t say what the rangers do specifically that leads to this effect,” noted Bessone. “It could be that rangers are a possible deterrent to poachers. Whatever the reason, it is clear that just the presence of law enforcement has a positive effect on bonobos.”

Another intriguing finding relates to the park’s southern side, home to traditional minority communities who have coexisted with bonobos for generations.

“In these villages there is a cultural taboo that prevents hunting of bonobo,” said Bessone. “It could be this that creates the positive effect they have on bonobo abundance.”

Benefits for bonobo conservation

Overall, the findings underline the importance of preserving forest cover and investing in law enforcement to ensure bonobo survival. Salonga’s long-term monitoring efforts have provided a model for other conservation initiatives across Africa.

“The biggest threats to bonobos are deforestation and commercial hunting, and our findings show that preserving forest and investing in law enforcement has concrete benefits for bonobo conservation,” said Fruth.

“We hope this motivates national and international conservation authorities to invest more into Salonga and other protected areas to ensure that bonobos remain part of our world far into the future.”

By combining decades of research with actionable recommendations, this study has laid a strong foundation for future conservation efforts, offering hope for one of the world’s most endangered species.

The study is published in the International Journal of Primatology.

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