Monkey Island

A Pennant’s red colobus monkey, one of the world’s most endangered primates, peers through the forest canopy on Bioko island.

Zookeeper Voyages to African Island to Support Primate Conservation

“That’s it, I’m going to die here,” I thought. The hike to camp was more than 7 kilometers—just over 4 miles—and most of it was up steep terrain. As the other volunteers and I struggled on sore feet and in sweat-drenched clothing, I took to calling the trail “The Widow Maker”. We had left at 8:20 a.m. and wouldn’t reach the camp until 5:15 p.m. Aching muscles, though, were a small price to pay to see two groups of wild black colobus monkeys.

That sight warmed our hearts. But the spent shotgun shell cartridge we found along the trail was a cold reminder of the danger these primates face every day.

Every January, volunteer researchers converge on Bioko, a tropical, volcanic island off the west African coastline of Cameroon, to conduct a three-week census of primates. The island’s remote Gran Caldera de Luba, a rarely visited reserve situated in an ancient crater, is home to 11 primate species. These primate subspecies populations—including monkeys and galagos (or bushbabies)—represent the densest concentration in Africa, and have evolved independently from their counterparts on the mainland since the island’s separation from the continent about 12,000 years ago.

The research team arrives at Moraka Playa. Bioko island’s separation from mainland Africa about 10,000 years ago helped nurture a remote haven rich in plant and wildlife species. Conservation initiatives such as an annual primate census and public education campaigns provide a vital response to poaching that’s led to declining populations.

I was invited to take part in this year’s census through an expedition led by the Bioko Biodiversity Protection Program (BBPP). The program is part of an academic partnership between Drexel University in Philadelphia and the Universidad Nacional de Guinea Ecuatorial (UNGE) in Malabo, Equatorial Guinea. Launched in 1998, its mission—shaped by founder and director Gail Hearn, Ph.D., a biology professor at Drexel—has been to preserve the rich biodiversity of species found on Bioko.

BBPP’s efforts span education, research and conservation initiatives promoting the value of indigenous wildlife sustainability. These goals have increasingly been threatened by poachers. The bushmeat crisis—commercial, illegal and unsustainable hunting for the meat of wild animals, many of them endangered species—provides short-term profit at a tragic cost in this oil-rich but impoverished region where institutional corruption has led to economic disparity.

Having never seen primates in their natural habitats, I was excited to get started! After 22 hours of air travel, we arrived in Malabo. Our lodgings in the nation’s capital were provided by Mobil Equatorial Guinea, Inc., a subsidiary of Exxon Mobil Corporation that provides funds to BBPP. From there it was a four-hour trip in a small motorboat to our first campsite at Moraka Playa. We were alarmed to learn upon arrival that BBPP personnel had confronted poachers using the beach campsite the previous day. The poachers had been told to leave and that their activities would not be tolerated.

A golden-bellied crowned guenon forages among the the treetops in the Gran Caldera de Luba, a 130,000-acre protected reserve home to a dense concentration of primate species. A weakly enforced hunting ban hasn’t deterred poachers from targeting monkeys for the illicit bushmeat market.

The research group selected for the 2013 expedition included volunteers from many backgrounds. There were college students, professors, photojournalists, filmmakers and graduate students. Each volunteer spent time in three different camps: Moraka Playa; Hormigas, situated between the beach and the caldera; and the Gran Caldera, which occupies the highest elevation on the southern end of the island. We were separated into small teams and led by local guides along several established trails through the forest in search of wildlife.

While our main objective was to collect data on monkey species, we also catalogued other animals we happened to encounter. We spotted several species of squirrel, blue and red duikers (small antelopes), tree hyrax (small, arboreal, rodent-like mammals), hornbills, porcupines and snakes. (View a photo slideshow of the expedition for more details on some of these species.)

The monkey subspecies we saw on Bioko include drill monkey, Bioko black colobus, Stampfli’s putty-nosed monkey, Bioko crowned monkey, Bioko red-eared monkey and Bioko Preuss’s monkey. (Black-and-white colobus monkeys can be seen at Lincoln Park Zoo’s Helen Brach Primate House and Regenstein African Journey.) The island is also home to a primate subspecies that doesn’t exist anywhere else: the Bioko Pennant’s red colobus monkey. It is recognized as the island’s first strictly endemic primate species and is critically endangered.

Every male red colobus monkey that we encountered threatened us, vocalizing and baring their teeth until we walked away. Luckily for them, we were just armed with cameras and notebooks. If they display this same behavior when they see hunters, they’re making themselves easy targets.

Two duiker species comprise Bioko’s native hoofed-mammal inhabitants. These small, elusive antelopes, like this Ogilby’s duiker, feed on fallen fruits and are prized by poachers. Their name derives from the Afrikaans word for “diver”, referring to their habit of diving for cover when disturbed.

BBPP’s first census expedition took place in 1990. Data collected annually since then helps researchers monitor how the endangered monkeys are faring in the face of increasing pressure from hunters. Based on the initial tabulation of our census reports, it seems the Bioko black colobus population is declining. One of the census teams found a complete colobus skeleton. The skeleton was collected and will be analyzed to gather as much information as possible on the animal, maybe even the cause of its death. Teams also collected at least a dozen spent shotgun shells.

Sadly, at least 24 native species are sold as bushmeat in local markets. These include monkeys, Emin’s giant pouched rats (so named for their large cheek pouches), duikers and sea turtles. The nesting season on Bioko for turtles—which include leatherback, hawksbill and olive Ridley species—peaks in January and corresponds to the dry season on the island, from September through April. Researchers are there during this time, and their presence alone is often enough to deter poachers.

Anita Yantz (right) enjoys a campsite break with Gail Hearn, Ph.D., the American biologist who founded the Bioko Biodiversity Protection Program, a partnership with the Universidad Nacional de Guinea Ecuatorial. Lincoln Park Zoo donors Mary and Bruce Feay fund these field-research opportunities to help zookeepers broaden their animal-care knowledge.

The expedition brought to light Bioko’s precarious situation. We are still learning about the island’s incredible biodiversity—as are the people who live there. With BBPP’s assistance, an educational documentary titled “The Drill Project” was recently filmed on Bioko to highlight the island’s endangered drill monkey species. The film was shown in Equatorial Guinea, and surprisingly, many Bioko residents who saw it had never heard of drills. The same production team took part in this expedition to make a documentary on the Pennant’s red colobus.

Thanks to such efforts and BBPP’s vigilance, the flora and fauna of Bioko have dedicated advocates. Ultimately, though, the island’s residents hold the greatest power for change.

Anita Yantz

Anita Yantz is assistant lead keeper of the Helen Brach Primate House. Her trip was made possible by the generosity of zoo donors Mary and Bruce Feay, who support annual field expeditions for Lincoln Park Zoo animal care staff.


Learn More

Bioko Expedition Slideshow
Learn more about the Bioko Biodiversity Protection Program’s primate census expedition and the island’s unique concentration of wildlife in this photo slideshow.

Update from the Arctic
Find out how Kovler Lion House lead keeper Anthony Nielsen collected permafrost samples in Manitoba, Canada, as part of an Earthwatch Institute Expedition gathering data for research on climate change.



Wow! What an incredible opportunity. There is nothing like being in nature and seeing it for yourself. I know it was a tuff journey, but I am sure it was worth it. Thank you for providing us with your pictures and information from your expedition. Awesome job!

Anita you did a fantastic job! This is a very concise report with beautiful pictures. I am so proud of you for going on this trip. It looks like you saw some beautiful places.

Congratulations to you and the other members of this expedition. Thanks to folks like you we can be kept aware of what is happening in remote places. Glad to have you back in town. I really enjoyed reading this informative report.


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