Sweeping census provides new population estimate for western chimpanzees

A sweeping new census published in the journal Environmental Research Letters estimates 52,800 western chimpanzees (Pan troglodytes verus) live in eight countries in western Africa, with most of them found outside of protected areas, some of which are threatened by intense development pressures.

Credit: Kimberley Hockings

The authors used IUCN’s Ape Populations, Environments and Surveys (A.P.E.S.) database, collating 58 survey datasets (three-quarters of which were unpublished) for the entire range of western chimpanzees. Using these data, the authors created a density and distribution map to look at trends and to identify drivers of those trends. Effort expended in the field totaled almost 11,000 kilometers of foot-surveys between 2001 and 2016.

Similar to results published last year by WCS on central chimpanzees and western lowland gorillas, the vast majority (estimated at around 52,000 individuals) live outside protected areas, and 10 percent of those live in areas that will be highly modified in the near future for “development corridors.”

The development corridors are large infrastructure projects aimed to promote economic integration and agriculture expansion, but are likely to cause further habitat loss and reduce population connectivity.

One way to reduce this environmental damage would be that developers of new infrastructure projects use these data to plan well ahead to avoid the most critical areas for these species and then take determined actions to minimize, restore, and offset any remaining impacts following guidance suggested by the Business and Biodiversity Offsets Programme (BBOP).

The study is led by Stefanie Heinicke of the Max Planck Institute for Evolutionary Anthropology and included WCS coauthors Terry Brncic and Boo (Fiona) Maisels. Brncic ran a wildlife survey of an entire country (Sierra Leone) while Maisels co-wrote the IUCN Best Practices Guidelines for surveying great apes, which were used in many of the surveys included in this paper.

The authors say the collation, curation, and long-term nature of taxon-specific databases is vital to studying and understanding trends in wildlife populations. The A.P.E.S. database is just such a tool, but the conservation world needs more of them, and for them to be well-funded in perpetuity.

Said Maisels: “This paper is a good example of how a well-designed taxon-specific database (in this case the IUCN’s A.P.E.S. database) is a powerful tool for drawing together numerous datasets in order to assess the status, distribution, and trend of an entire subspecies. Very few such databases exist and the paper makes a call for more of them to be created, and, importantly, for these new ones and the existing ones to be better funded.

Source: Wildlife Conservation Society [March 29, 2019]

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