Model results comparing deviance values and percentage of deviance explained.

<p>Model results comparing deviance values and percentage of deviance explained.</p

The mean (centre) and 95% confidence interval (left: lower bound; right upper bound) of the gorilla distribution range using the same boundaries as Fig 2.

<p>The mean (centre) and 95% confidence interval (left: lower bound; right upper bound) of the gorilla distribution range using the same boundaries as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162697#pone.0162697.g002" target="_blank">Fig 2</a>.</p

The mean (centre) and 95% confidence interval (left: lower bound; right: upper bound) of the probability of presence for Grauer’s gorilla.

<p>The maps also show the location of cells sampled (grey dots) with cells where gorilla sign was observed (black crosses).</p

Map of the probability of presence for Grauer’s gorilla.

<p>Occupancy probability was mapped using three covariables (tree cover, altitude and distance to recent deforestation) and a spatial autocorrelation (left panel). The probability threshold maximising the TSS was 0.35. This threshold was used to derive a gorilla distribution range (upper right panel) for which presence probabilities were greater than this value (grey = less than 0.35).</p

Catastrophic Decline of World's Largest Primate: 80% Loss of Grauer's Gorilla (<i>Gorilla beringei graueri</i>) Population Justifies Critically Endangered Status

<div><p>Grauer’s gorilla (<i>Gorilla beringei graueri</i>), the World’s largest primate, is confined to eastern Democratic Republic of Congo (DRC) and is threatened by civil war and insecurity. During the war, armed groups in mining camps relied on hunting bushmeat, including gorillas. Insecurity and the presence of several militia groups across Grauer’s gorilla’s range made it very difficult to assess their population size. Here we use a novel method that enables rigorous assessment of local community and ranger-collected data on gorilla occupancy to evaluate the impacts of civil war on Grauer’s gorilla, which prior to the war was estimated to number 16,900 individuals. We show that gorilla numbers in their stronghold of Kahuzi-Biega National Park have declined by 87%. Encounter rate data of gorilla nests at 10 sites across its range indicate declines of 82–100% at six of these sites. Spatial occupancy analysis identifies three key areas as the most critical sites for the remaining populations of this ape and that the range of this taxon is around 19,700 km². We estimate that only 3,800 Grauer’s gorillas remain in the wild, a 77% decline in one generation, justifying its elevation to Critically Endangered status on the IUCN Red List of Threatened Species.</p></div

Changes in encounter rate at 10 sites across Grauer’s gorilla range.

<p>Changes in encounter rate at 10 sites across Grauer’s gorilla range.</p

Estimated density of gorillas at five sites from line-transect surveys.

<p>Estimated density of gorillas at five sites from line-transect surveys.</p

Proportion of protected areas with conservation activities between 1990 and 1999 across different African regions.

<p>The number of protected areas with available information on presence and absence of any conservation activity (research, tourism and law enforcement guards) over the considered period were in total 105.</p

Influence of tourism activities and PA size on threat level in 83 PAs.

<p>In bold are highlighted significant values (p <i><0.05</i>). See abbreviations in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114154#pone-0114154-t002" target="_blank">Tab 2</a>. AIC, Akaike's Information Criterion; AICw, Akaike Information Criterion weight; Rank, model rank from the smallest to the largest AIC value; k, number of variables including the intercept.</p><p>Influence of tourism activities and PA size on threat level in 83 PAs.</p

Regional distribution of the protected areas (PAs) in tropical Africa considered in the analyses.

<p>The regions are coloured in different grey scale colours. Light grey represents West Africa, including 54 protected areas; medium grey represents Central Africa, including 31 protected areas; dark grey represents East Africa, including 14 protected areas. On the left-side bottom corner a MODIS NDVI image of Africa, with a red quadrant highlighting the tropical area considered in the study.</p