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A Population Assessment of the Critically Endangered Dryas Monkey in the DRC

dryas monkwy

This dryas monkey was photographed with a motion-sensor
game camera trap during the study.

Daniel Alempijevic, Spring 2016

Congolese forests contain some of the most diverse primate communities, yet many are poorly studied. The Lomami River basin is one of the most remote forests in DR Congo. The Lukuru Foundation documents the region's biodiversity and initiated the establishment of Lomami National Park (LNP). Two years after a new species, lesula (Cercopithecus lomamiensis), was described, the foundation had another exciting discovery: an unknown population of dryas monkeys, Cercopithecus dryas. A hunter's kill identified in the LNP buffer zone represented a range expansion of this poorly known and critically endangered species, thought to be restricted to forests around the Wamba and Kokolopori Bonobo research sites (400 km [249 mi] to the north). The Lukuru Foundation has conducted several camera trap surveys and recorded primate encounters on thousands of kilometers of park patrols but never detected dryas monkeys until 2014.

I joined Kate Detwiler's primatology lab in 2015, tasked with studying this new population. We developed the study with the Lukuru Foundation's scientific director, John Hart, to execute a multistratum camera trap survey. Our primary goal was to develop a species-specific camera trap placement method to detect dryas monkeys. With the help of local hunters, we placed 10 vertical camera-trap columns in degraded forest in the LNP buffer zone, then moved the cameras to a mixed-mature forest site in the park. We repeated surveys at both sites, using a strategically placed camera trap grid to reduce detection bias and increase coverage within the survey area in 2017. We successfully obtained photos and video of dryas monkeys and 9 other primates. This study suggests that dryas monkeys prefer disturbed forest sites with floristically complex understories. 

The camera trap videos gave us insight into C. dryas' diet, vocalizations, and mixed-species associations. We recorded 27 videos during the study, and we are hoping to continue the research by increasing the number of cameras in the understory to improve our detection of this rare and mysterious species. We thank PCI for its support for this study.

  David Alempijevic    
Daniel Alempijevic (left) climbing a tree to place a camera trap in the canopy for monitoring dryas monkeys.   Project team members (from left): John Konga Bakoni, Pablo Ayali, Jean Pierre Kapale, Marten Balimu.

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