Population management as a tool in the recovery of the critically endangered Western Derby eland Taurotragus derbianus in Senegal, Africa

Abstract

AbstractThe critically endangered Western Derby eland Taurotragus derbianus derbianus, representing < 200 wild individuals, undoubtedly needs a coordinated conservation programme. To promote the survival of this subspecies, a single worldwide semi‐captive population was established in Senegal in 2000, with one male and five female founders transferred from the Niokolo Koba National Park. To determine a long‐term conservation strategy, we used demographic and pedigree data based on continuous monitoring of reproduction during 2000 ‐ 2009 in breeding enclosures in the Bandia and Fathala Reserves, in conjunction with modelling software. In 2009, the semi‐captive population consisted of 54 living individuals (26 males and 28 females), managed using the minimal kinship strategy. The female breeding probability was 84%, annual calf and adult mortality rates were 5.09% and 3.27%, respectively, and the annual population growth rate was 1.36. As the population grew, the animals were progressively separated into five herds within two reserves. A pedigree analysis revealed an effective population size of 6.72 and an Ne/N ratio of 0.13. The population retained 77% of the gene diversity (GD). The founder genome equivalent (FGE = 2.21) was relatively low due to the overrepresentation of one founder male. Although the mean level of inbreeding (F) reached 0.119, a significant potential GD (92%) was still retained. In this article, we predict GD development in this population in the next 100 years with the inclusion of new founders. If the whole wild population were included, we could maintain 90% of GD. As this option is not practically feasible, we present three options with the goal of maintaining 75% GD. We highly recommend capturing new founders from the remaining wild population to ensure the survival of the subspecies at least in semi‐captivity, which could allow possible reinforcement of the wild population or reintroduction in the future. The semi‐captive population, if appropriately constituted and genetically managed, could play a considerable role in Western Derby eland conservation.