The West African Chimpanzee is listed as Critically Endangered on the World Conservation Union (IUCN) Red List. The Nimba Mountains Nature Reserve, a UNESCO World Heritage Site on the border between Guinea, Liberia and Côte d’Ivoire in West Africa, is home to a unique population of this chimpanzee species. But Guinea is also rich in minerals and has some of the highest quality iron deposits in the world. The region is threatened by mining that is taking place on the border of the reserve. ’It is therefore crucial that we develop tools to monitor the endangered chimpanzee population and assess the impact of mining,’ says Kathelijne Koops, professor at the Institute of Evolutionary Anthropology at the University of Zurich.
Fecal samples collected from over 15 yearsTo determine the size of the chimpanzee population, community composition and its range on the western flank of the Nimba Massif, Koops and her colleagues used genetic counts. The international team included researchers from the Universities of Zürch, Kent and Copenhagen, the Copenhagen Zoo, Texas A&M and the Bossou Environmental Research Institute in Guinea.
Between 2003 and 2018, the scientists collected nearly a thousand chimpanzee fecal samples during fieldwork. They analyzed the genetic material contained in them using a panel of 26 microsatellites - short pieces of DNA that allow the identification of individual animals as well as the relationship between them. ’Our study is the first to use genetics so extensively to determine the numbers and population structure of a highly threatened chimpanzee population in West Africa,’ Koops says.
Genes reveal family ties and migration patternsThe analysis revealed a total of 136 chimpanzees living in four distinct communities or social groups. The actual number of chimpanzees in the area likely greatly exceeds this minimum estimate. ’Infants and juveniles are not reliably recorded via the fecal samples, and there are not enough fecal samples from some areas of the range,’ says Christina Hvilsom, a geneticist at Copenhagen Zoo.
The team also identified a number of migratory movements, a high degree of common ancestry and great genetic diversity in the chimpanzee population. ’The results underline the usefulness of genetic census to monitor monkey populations over time, but also to track migration movements, genetic diversity and population viability,’ adds co-author Peter Frandsen, also of Copenhagen Zoo. The data can be used, for example, to predict how road construction and mining activities might affect chimpanzee movements between different communities or access to food and nesting sites.
New tool to protect great apes’Our study confirms the status of the UNESCO World Heritage Site of Nimba as a priority area for the conservation of the critically endangered West African chimpanzee,’ says co-author Tatyana Humle, senior associate at Re:wild. It also shows the value of using non-invasive genetic techniques to gain important data on population abundance, structure and genetic health, she adds.
’For future impact assessments, we recommend genetic sampling in combination with camera trapping, as these methods can provide robust baselines for biomonitoring and conservation management,’ says Koops. This applies not only to the West African chimpanzee, but also to other endangered great ape species.