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.