Maisels F, Bergl R & Williamson EA (2016) Gorilla gorilla. IUCN Red List [IUCN Red List Assessment web page] 2016. http://www.iucnredlist.org/details/9404/0
Justification: Gorilla gorillahas a large geographic range, covering over 700,000 km². The size of the population is currently being evaluated, but thought to be in the order of a few hundred thousand (Strindberg et al. in prep). Only a very small number of Western Gorillas are the G. g. diehli subspecies, therefore this rationale focuses on the G. g. gorilla subspecies. The country of Gabon lost over half its Gorilla population between 1983 and 2000 (Walsh et al. 2003). More recent population declines have been estimated using a predictive model that incorporated survey data collected between 2003 and 2013 across the entire range of Western Lowland Gorillas. The results reveal an 18.75% decline between 2005 and 2013, corresponding to an annual loss of ~2.56% (Strindberg et al. in prep). These population decreases were driven by poaching and disease (Ebolavirus) outbreaks.Despite their abundance and wide geographic range, Western Gorillas qualify as Critically Endangered under criterion A: a population reduction of more than 80% over three generations (one generation is ~22 years). This listing is based on ongoing population losses due to illegal hunting, disease and habitat loss: poaching is intensifying with the expansion of access routes into forests and Zaire Ebolavirus remains a highly significant threat. At a conservative rate of reduction (2.56% per year rather than 4%, calculated from Walsh et al. 2003), the reduction in the Western Gorilla population is predicted to exceed 80% over three generations (i.e., 66 years, 2005-2071). Illegal hunting has not ceased despite intense anti-poaching efforts, and the threat of Ebolavirus has not been removed. In addition, the scale of habitat conversion to industrial agriculture will increase, and the effects of climate change will become more evident.Gorilla gorillathus qualifies as Critically Endangered (A4bcde).