Genetic and demographic analysis of European Endangered Species Programme (EEP) and Species Survival Plan (SSP) Western lowland gorilla Gorilla gorilla gorilla populations

Abstract

Since the late 1990s, European Association of Zoos and Aquaria (EAZA)‐member zoos have worked collaboratively to achieve a self‐sustaining population for gorilla through the European Endangered Species Programme (EEP). The Association of Zoos and Aquariums (AZA) in the United States has similarly worked through the Species Survival Plan (SSP). These populations are all registered in the International Studbook for the Western Lowland Gorilla Gorilla g. gorilla Savage & Wyman, 1847, which is updated annually. Demographic and genetic analyses of these data are carried out to monitor population development. This paper presents the results of the genetic and demographic analysis of EAZA and AZA populations of the Western lowland gorilla Gorilla gorilla gorilla, considering the individuals registered since the beginning of the studbook (1950) until 2014, and the analyses are mainly focused on the results for both populations around the last decade. The data have been gathered from the 2014 international studbook and data registered in the Single Population Analysis and Records Keeping System (Sparks). Genetic and demographic analyses were carried out using PMx software. The results of the demographic analyses show that the EEP population is growing, demonstrating positive life parameters; for example, a finite growth rate of λ = 1·007, an instantaneous growth rate of r = 0·007 and a net reproductive rate of R0 = 1·160. However, the results of the demographic analyses for the SSP population show a general tendency for population reduction; that is, a finite growth rate of λ = 0·992, an instantaneous rate of growth rate r = −0·008 and a net reproductive rate of R0 = 0·864. When comparing the results from both populations it would appear that the application of strict breeding policies in the SSP for a few years had a noticeable impact on the SSP demographic results.