On a July day in 2014, biologists Henri Silegowa and Jean Pierre Kapale were buying rice in Bafundo, a village in the Democratic Republic of the Congo, when they noticed a dead monkey about to be cooked as bushmeat. In seven years of surveying the region’s primates, neither they nor their colleagues at the Lukuru Foundation’s TL2 Project had laid eyes on a monkey like this.
“We were inside the fenced compound of a local woman, buying rice for our patrol teams, when I saw this tiny monkey hanging off the side of the kitchen. I’d never seen anything like it, and the woman said she did not know its name,” Silegowa recalls.
The specimen was a small female, the size of a housecat. Her black face was cushioned in lushrusset fur and haloed by a white diadem. She had a pale blue rump. The hunter, when Silegowa tracked him down, called the monkey inoko. He’d traded the carcass for a few measures of rice.
John Hart, scientific director of the TL2 Project, described her as “beautiful,” a “miniscule little animal.”
At first, Silegowa and Hart thought the monkey might be new to science.
“I checked our field guides, and couldn’t find anything that matched the photo we had of the inoko,” Silegowa says. “There was not a single monkey in the field guide with that black face rimmed by orange, and with blue buttocks.”
Hoping for more information, the TL2 Project posted a photo of the mystery monkey on its blog. Comments trickled in from researchers as far away as Japan and the U.S., identifying it as the dryas monkey (Cercopithecus dryas), the smallest member of the genus of monkeys known as guenons. The species was first described in 1932 by a German zoologist, Ernst Schwarz, but it was only known from a tiny patch of forest in the Wamba-Kokolopori region, nearly 400 kilometers (250 miles) to the northwest. Not surprisingly, at the time, the IUCN classified the species as critically endangered.
The revelation struck Silegowa as a “big surprise.”
“We knew we had found something special,” he says.
So how did this little dryas monkey end up hanging as bushmeat in Bafundo?
Bafundo sits in the Congo Basin, the world’s second-largest tropical rainforest, on the border of Lomami National Park. The region is a sparsely populated wilderness known as TL2 for the three rivers — Tshuapa, Lomami and Lualaba — that drain it toward Africa’s center.
The TL2 Project, founded in 2007, has discovered biological riches here including bonobos (Pan paniscus), the striped giraffe-like animal known as the okapi (Okapia johnstoni), and around 700 African forest elephants (Loxodonta cyclotis). In 2012, the team even stumbled upon a species of monkey unknown to science, which they named lesula (Cercopithecus lomamiensis).
When the bushmeat dryas appeared, the researchers had trouble believing this forest held yet another surprise for them.
“At seven years in, they get this animal showing up dead in a village that they had no idea was there!” says Daniel Alempijevic, a graduate student at Florida Atlantic University who works with the TL2 Project. “The big surprise was, how has this [monkey species] been going under the radar for so long now?”
Alempijevic came in to tackle that question by setting up dozens of “multi-strata” camera traps in Lomami National Park and its buffer zone. Nobody knew where to look for the dryas, so he and his mentor, Kate Detwiler, an anthropologist at Florida Atlantic University, decided to place cameras on the ground, in the understory, and up in the canopy, sometimes at a dizzying 30 meters (100 feet) high.
In the first month, not one of his cameras caught a dryas, but in the second round his persistence was rewarded with a few tantalizing seconds of video.
“That first time we got one on a camera, I was just thrilled,” Alempijevic says. “After that, they just started trickling in. Now, it’s actually not an irregular sighting in the understory. It’s one of the more common monkeys we’re getting in that stratum.”
An innovative strategy of placing camera traps at multiple levels in the forest has earned researchers an hour-and-a-half of footage of the elusive dryas monkey. This video collage includes the highlights. Video courtesy of Daniel Alempijevic/Primatology Lab/Florida Atlantic University, Ephrem Mpaka and Koko Bisimwa/TL2 Inoko Project/Frankfurt Zoological Society.
Camera trap results show that dryas monkeys rarely venture up to the canopy, and the cameras have yet to catch them on the ground. Their preferred habitats are dense, swampy vine thickets in the understory, especially gaps where an old tree has fallen and dragged its tangle of woody lianas and skin-ripping rattans down with it.
“It is a really difficult environment to penetrate,” Alempijevic says. “Total bushwhacking to get in. Lots of spines. I’m still pulling rattan spines out of my skin from a year ago!”
This might explain how dryas monkeys have evaded human notice for so long. But now, thanks to the cameras, scientists have accumulated a total of an hour-and-a-half of footage.
“We’re seeing so much more on the cameras than we could ever see with our eyes,” Alempijevic says.
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