Bonobo populations in the Democratic Republic of Congo‘s Salonga National Park remained steady between 2002 and 2018, but there are worrying signals of decline, a recent study has found.
For decades, Salonga has been known to host the largest known population of bonobos (Pan paniscus), an endangered great ape found only in the DRC. However, researchers didn’t have a reliable estimate for bonobo numbers in the massive park, which spans more than 33,000 square kilometers (12,700 square miles) and includes a 9,000-km2 (3,500-mi2) corridor of human settlements.
Over the years, researchers have used different methods to count bonobos in Salonga. But those surveys have been “too small and patchy,” and over short time periods, according to the new study’s authors. So they reanalyzed 13 surveys conducted between 2002 and 2018, reconciling the different methods to understand bonobo numbers and distribution across the entire park and across multiple years, Mattia Bessone, the study’s lead author from the Max Planck Institute of Animal Behavior, Germany, told Mongabay by email.
The reanalysis showed the park has been home to between 8,000 and 18,300 adult bonobos since 2002. This estimate conforms to extrapolations made in 2008, Bessone said.
The study also found that bonobos were present more often near ranger patrol posts. Bessone said the reasons for this aren’t clear, but the presence of rangers could serve as a deterrent to hunting of bonobos, which are a protected species. “We have not investigated if the same applies to non-protected species (we suspect that it does not), but the effect on bonobos is remarkable and support strategies including law enforcement as a conservation tool,” Bessone said.
Bonobo presence was generally lower closer to villages, the study found, except for some located in the park’s south. There, people “have a taboo against killing bonobos,” Bessone said.
“It is commendable that the authors have brought these findings together in such a comprehensive manner,” Erin Wessling, a great ape researcher at Harvard University, U.S., who wasn’t involved in the study, told Mongabay by email.
However, the study hints at some troubling signs. While bonobo populations and distribution haven’t changed much in Salonga since 2002, there was a slight decline over the years.
“Although not [statistically] significant, these results suggest that bonobos are far from being safe even in Salonga and encourage further effort to protect the species within the Park,” Bessone said.
The authors haven’t probed the reasons for the decline, but Bessone said poaching in some remote parts of the park, like in the southwest, where park rangers are rarely present even today, could be a factor. Climate change could also be affecting the bonobos’ food availability, he added.
The potential decline in bonobo populations in Salonga, which is well-studied, “serves as a stark reminder that less monitored and less protected areas might very likely be experiencing more severe declines,” Wessling said.
This article by Shreya Dasgupta was first published by Mongabay.com on 10 January 2025. Lead Image: Bonobos, courtesy of Christian Ziegler/Max Planck Institute.
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