Primates don't get much more spectacular than the furry, short-tailed, long-faced, pink-rumped monkeys known as drills (Mandrillus leucophaeus). But despite their striking looks, drills—which are closely related to baboons and the even more wildly colored, blue-faced mandrills (M. sphinx)—have not fared well in the wild over the past few decades. Drills have become one of the most endangered primate species in Africa, with an estimated population as low as 3,000 animals. Now new research shows that drills have been hunted and pushed out of most of their historic habitat, leaving few remaining territories where they can safely thrive. The study, published in the April 2013 issue of the International Journal of Primatology, suggests that active conservation may be necessary to safeguard the remaining drill habitats and keep the species from extinction.
According to the study, 80 percent of the world's remaining drills live in Cameroon. Unfortunately for the primates, Cameroon's human population has surged from 15.4 million in 2000 to more than 20 million in 2012. Meanwhile its economy has also grown, especially in the areas of palm oil plantations and oil exploration. That rapid expansion has put the squeeze on drills and their habitats.
The researchers—from the Zoological Society of San Diego and other institutions—divided the drill's historic habitat in Cameroon into 52 zones, then conducted field surveys and village interviews to find out where drills remained. The results were not encouraging—the researchers only found direct evidence of drills in 16 zones. They also ranked each zone for its suitability to sustain drill populations, and those results were even worse. Only four sites ranked highly on their scale, indicating that they had the high levels of tree cover, less hunting, more law enforcement and more local recognition that drills are a protected species under Cameroonian law. The four sites also had populations of chimpanzees and elephants, indicating that the government would be more inclined to stop poaching in those regions.
In the less optimal habitats the researchers found that many drills are stuck in tiny forest fragments within landscapes dominated by human development. This leaves the animals with few opportunities to migrate and disperse their populations as generations mature. For example, there are small populations on both Mount Kupe and Mount Manenguba, but each is separated from the other by several kilometers of agricultural development.
Despite the drill's legally protected status, the researchers also found that the animals were frequently hunted, often with the assistance of hunting dogs, which drive the primates up into trees where they can all easily be shot. Drill groups usually stay together rather than scatter when threatened by predators such as dogs. The researchers say the bushmeat trade drives much of the hunting, with middlemen providing villagers with guns and ammunition and then trading any animals collected for alcohol or illegal drugs.
That's where things stand today, and the researchers wrote that the future might be even worse. Several planned new oil palm plantations could carve out even more of the drill’s current habitat. One 210,000-hectare plantation would cover the entirety of one of the study's 52 zones, as well as significant portions of two others.
So what comes next? The researchers hope that this study can be used to identify the best areas necessary for the drill's long-term survival. In particular, the study gives extra support to the proposed Ebo National Park, which has been in the works for several years and could end up protecting more than 110,000 hectares of biodiversity-rich forest. That pales in size when compared with some of the palm oil plantations, but for the drill, it's certainly better than nothing.
Photo: A male drill at Limbe Wildlife Center in Cameroon, photographed by Bernard DuPont. Used under Creative Commons license
Previously in Extinction Countdown: