Cameroon’s Korup National Park is home to elephants, chimpanzees, red colobus monkeys, drill, and a myriad of noisy species, whose squawks, squeals and howls fill the forest air. For more than two years, twelve acoustic monitors were deployed there and recorded every sound covering a 54 square kilometer (21 square mile) area of protected tropical forest.

They were tuned to listen around the clock for just one sound: gunshots.

“Our ultimate goal is to improve the effectiveness of anti-poaching patrols in African tropical forest protected areas,” Joshua Linder, one of the lead scientists working on the acoustic monitoring project, told Mongabay.

Bushmeat is a major source of protein in Central Africa, with 4.5 million tons extracted from the Congo Basin each year. Taking bushmeat itself is not always illegal, and it can be a vital source of protein for the poor and a valued commodity for the rich. But hunting endangered species, especially within protected areas, is against the law. It can pose a real threat to the survival of animal populations, and particularly to rare species.

map-1Korup’s proximity to Nigeria, just a few kilometers away, makes it attractive to poachers. “[M]uch of the demand comes from Nigeria as well as urban centers in Cameroon,” Linder said. “Hunting of wild meat is very commercialized now. There are professional hunters who earn most of their annual income just from hunting. Nigerian hunters come into Korup to hunt and bring the meat back to Nigeria where it fetches a higher price than in Cameroon.”

The research team is trying to address the poaching threat in what he describes as “one of the most important protected areas in Africa’s Gulf of Guinea region.” Project collaborators include Linder of James Madison University, Peter Wrege of Cornell University, and Christos Astaras and David Macdonald of the Wildlife Conservation Research Unit, University of Oxford; they are joined by Cameroon-based conservation organizations.

Theirs is an urgent task: “Our acoustic monitoring project suggests that thousands of primates are killed by illegal gun hunting annually in Korup,” the team told Mongabay.

Duikers, rodents, and even elephants are hunted in Korup too, but it is the primates that are of greatest concern to conservationists.

“My own research in Korup shows that hunting is leading to declines in some of Africa’s most threatened primate species,” Linder added, such as the Critically Endangered Preuss’s red colobus (Procolobus preussi), one of the world’s 25 most endangered primates — an animal endemic to western Cameroon and parts of Nigeria. Korup is a critical stronghold for the species. A second Endangered primate, the drill (Mandrillus leucophaeus), is also declining, Linder said.

By monitoring poaching activity continuously for over two years, the team was able to gather data on hunting patterns in unprecedented spatial and temporal detail. Using that data, “Protected area managers can then design anti-poaching patrols,” evaluate their impact, and adapt patrols in response to new data, the team explained.

The research has been revealing. Hunting is highest early in the week, as poachers ready for markets that most commonly occur on Saturdays. Hunting occurs year-round, but peaks during the November-to-March dry season, and before major holidays. The preferred hunting locations within the project area were also pinpointed, the team said.

“None of this information was previously available to park managers,” Linder noted. The analysed data could help tell park law enforcement not only where they’ll most likely find poachers, but when.

The project has not been without its challenges. The dozen acoustic monitoring sensors — each with a detection radius of 1.2 kilometers (0.75 miles) — run on heavy batteries that need to be carried through the forest over rugged terrain and changed every three months. Also, more than 200,000 hours of recordings were gathered (equivalent to nearly 23 years) which takes a lot of computer storage and analysis, aspects of the research that should not be underestimated in future projects that may adopt this technology, the team warned.

The monitors themselves can also be used to address other questions: future plans include deploying the sensors to study human-wildlife conflict, particularly with elephants, and to help locate unprotected populations of Preuss’s red colobus living beyond Korup’s boundaries.

The team shared their project findings with Nigerian and Cameroonian protected area managers at a conference late last year, and they now hope to convince other land managers to adopt the eavesdropping technology. The technique could ultimately have value for protected areas, law enforcement, and conservation researchers trying to track and curb poaching across Africa and around the world.

Meanwhile, back in Korup, the researchers’ work is already having an impact: “We recently helped park managers design a comprehensive wildlife monitoring program for the whole park that includes acoustic monitoring.”

“I’m hopeful that acoustic monitoring combined with other strategies can help to reverse this trend” in hunting, Linder said.

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