Chimpanzee populations in Uganada greater than previously thought

 Chimpanzees (Pan troglodytes) are currently listed as endangered by the International Union for the Conservation of Nature (IUCN) due to threats from habitat loss and degradation causing a decrease in population numbers that will likely continue (Oates et al., 2008). However, a recent study examining chimpanzee numbers in Uganda gives us reason to hope for our close primate relatives. In the open access journal BMC Ecology, McCarthy and colleagues report that 15 months of data collection has lead them to determine that over two hundred and fifty chimpanzees live in a corridor that was previously assumed to hold ~seventy individuals.

Chimpanzees with offspring, Photo credit: flickr user Valerie

The Budongo and Bugoma Forest Reserves in Uganda are two large areas of protected land separated by an unprotected area that contains villages, agricultural fields, along with grasslands and forest. It's not your typical, ideal chimpanzee habitat. This corridor is dominated by humans, with 107 humans per square km (NPHC, 2014). Yet, studies like this one have obvious merit as we lose more and more pristine habitat.

Researchers collected fecal samples and genotyped those samples from 2011-2013. They then used models to determine the number of individuals. This noninvasive method is more accurate than counting the number of nests chimpanzees make at night in order to determine the number of individuals. (Chimpanzees make nests out of branches and forest materials every night that they sleep in. See a video here.) Using this method, they were able to determine that there are at least nine communities, each with anywhere between eight to thirty-three individuals. Because not all areas of the unprotected corridor were not sufficiently sampled in this study, it is possible this is a conservative estimate, and numbers may be even higher.

McCarthy and colleagues point out that chimpanzees exhibit a great deal of behavioral flexibility, which likely accounts for how they've coped with a less-than-ideal environment. Chimps are omnivores and can adapt their diet if they need to, including human-cultivated foods. Provided a lack of pressure from hunting, it is worth considering these stretches of land that previously may have been overlooked as viable areas worthy of conserving. The next steps will be understanding just how the chimps are doing so well in this habitat. What behavioral changes are they making?

Links of interest:
IUCN Redlist page on chimpanzees 
Map showing current range of chimpanzees 
The fate of western lowland gorillas and chimpanzees over the next decade
How human are chimps?

Works cited:
Maureen S McCarthy, Jack D Lester, Eric J Howe, Mimi Arandjelovic, Craig B Stanford, Linda Vigilant. Genetic censusing identifies an unexpectedly sizeable population of an endangered large mammal in a fragmented forest landscape. BMC Ecology, 2015; 15 (1) DOI: 10.1186/s12898-015-0052-x
NPHC 2014 provisional results report. Uganda Bureau of Statistics, Kampala; 2014.
Oates, J.F., Tutin, C.E.G., Humle, T., Wilson, M.L., Baillie, J.E.M., Balmforth, Z., Blom, A., Boesch, C., Cox, D., Davenport, T., Dunn, A., Dupain, J., Duvall, C., Ellis, C.M., Farmer, K.H., Gatti, S., Greengrass, E., Hart, J., Herbinger, I., Hicks, C., Hunt, K.D., Kamenya, S., Maisels, F., Mitani, J.C., Moore, J., Morgan, B.J., Morgan, D.B., Nakamura, M., Nixon, S., Plumptre, A.J., Reynolds, V., Stokes, E.J. & Walsh, P.D. 2008. Pan troglodytes. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>.