“The main reasons lesula has remained unknown to western scientists for so long are its remoteness – it inhabits a small and very restricted range in an extremely dense forest in Congo – and its shyness,” said James Fuller, co-author of the scientific paper and a Ph.D. student in the Department of Ecology, Evolution, and Environmental Biology (E3B) at Columbia University. “Our publication, and the analyses that went into it, made it possible to classify the species.”
The new primate, described in a paper published this week in the open access scientific journal PLOS ONE, was first spotted in a school director’s compound in the town of Opala in 2007. Initially, the study authors, conservation biologists Dr. John Hart and his wife Dr. Terese Hart of the Lukuru Wildlife Research Foundation in Kinshasa, and their team, thought the young female captive Lesula resembled an owl faced monkey…. however, closer examination revealed a markedly different appearance.
“The first indication this was a distinct species was its pelage… though similar to the Owl-faced monkey (Cercopithecus hamlyni) to which it is most closely related, there are clear differences in coloration, especially in the face (lesula is lighter and the nose stripe is much less conspicuous),” said Fuller. “Previous ‘new species’ have been designated based solely on differences in appearance, but the research team wanted to take a comprehensive approach.”
Over the next year, the research team obtained bones and tissue samples from dead lesula (killed by local hunters for bushmeat trade and one unlucky eagle that failed to carry off its prey) and from a few captive animals kept as pets by local people. The researchers then compared these samples to one another using a variety of techniques to determine the evolutionary relationship between lesula and closely related species.
“Morphological comparisons using cranial measurements of other primates clearly indicated that lesula was within the genus Cercopithecus, and most closely resembled the Owl-faced monkey (C. hamlyni) yet was morphologically distinct,” said Fuller.
By conducting genetic and molecular analyses and comparing field-recorded vocalizations (the “boom call”), the researchers determined that lesula and the owl-faced monkey are distinct species which likely diverged from a common ancestor 1 to 2 million years ago.
While the team does not know the exact distribution of lesula or its population size, the best censuses estimate that the lesula habitat is limited to an area of about 17,000 square kilometers within the Tshuapa-Lomami-Lualaba Conservation Landscape (TL2). Like many of Africa’s primates, the lesula is in danger from a suite of growing environmental pressures.
“One of our many hopes is that the discovery of lesula will highlight the diversity of rain forests that we have yet to understand, before it is too late, and to bring conservation attention to this important and extremely remote part of the world, said Fuller. “The biggest threat to the wildlife of this area at the moment comes from commercial bushmeat hunting, a trend that has been rising steadily in recent years and that promises to increase as the human population continues to grow. Though its remoteness has, for the moment, slowed some of the decline experienced by other forests around the globe, the TL2 is relatively small, and species with small, restricted ranges (like the lesula) are especially vulnerable.”
The Lukuru Foundation, whose mission “is to conserve great apes and their natural habitat within the territorial borders of the Democratic Republic of Congo,” is working hard to protect the area’s endemic and endangered species. The foundation members hope that the new found popularity of lesula will increase understanding of the importance of this area.
Looking toward the future, Fuller remarked that “…we still know very little about this species’ behavior and ecology… we are only just beginning to collect data on their behavior and habits. The next few years promise to be very exciting as we learn more about this species.”