Guns, germs, and trees determine density and distribution of gorillas and chimpanzees in Western Equatorial Africa.

We present a range-wide assessment of sympatric western lowland gorillas and central chimpanzees using the largest survey data set ever assembled for these taxa: 59 sites in five countries surveyed between 2003 and 2013, totaling 61,000 person-days of fieldwork. We used spatial modeling to investigate major drivers of great ape distribution and population trends. We predicted density across each taxon's geographic range, allowing us to estimate overall abundance: 361,900 gorillas and 128,700 chimpanzees in Western Equatorial Africa-substantially higher than previous estimates.

Western gorilla diet: a synthesis from six sites.

The objective of this paper is to collate information on western gorilla diet from six study sites throughout much of their current range, including preliminary information from two sites (Afi and Lossi), where studies of diet have begun only recently. Food lists were available from each site, derived from indirect signs of gorilla feeding (such as feces), with some observational data. Important staple, seasonal, and fallback foods have been identified, and a number of striking similarities across sites have been revealed based on a much larger data set than was previously available.