Individual-based assessment of post-translocation fitness of ungulates: Lessons from the critically endangered Derby eland conservation programme

Abstract

Translocations have become an essential tool in animal conservation for establishing and maintaining viable populations. Yet, the viability of a population is implicitly based on the individual fitness, that is on the survival and reproduction of individuals. Individual-based assessments of post-translocation fitness are challenging in the wild while conservation breeding programs may provide vital insights. Long-term breeding records of semi-captive (fenced) small population of the Western Derby eland (Taurotragus derbianus derbianus) running in two fenced reserves in Senegal present a case study. This study shows that transport distance and the individual's age at translocation influence animal post-translocation survival rates and individual reproductive performance. The most critical period for the antelope's post-translocation survival was the first 2 years following the event, with higher mortalities reported after long-distance transport in an ecologically novel environment. The first successful calving of translocated females was postponed by 1 year, but the life-long reproductive performance was not affected. However, higher calf survival in a habitat similar to that in the wild suggests a non-negligible effect of the habitat on individual fitness, thus crucial to conservation decisions on translocating threatened species.