Population and trophy quality trends of three gregarious herbivores in an insulated semi-arid savanna ecosystem (Cawston Ranch, Zimbabwe), 1997-2014

Abstract

Long term monitoring of population estimates and trophy size trends is needed to ensure that trophy hunting is sustainable. We explored the influence of trophy hunting on population size and trop hy quality of impala (Aepyceros melampus), greater kudu (Tragelaphus strepsiceros) and sable (Hippotragus niger) antelopes from 1997 to 2014 in Cawston Ranch, Zimbabwe. Population estimates of the three species showed a cyclical declining trend, albeit statistically not significant for the three species. Hunting pressure had no significant effect on the population estimates of the three species for the period 1997-2014. Impala population declined (-30 %) between 2003 and 2008 possibly due to increased illegal hunting associated with land invasions during this period. Trophy size of all species declined over time, 2004-2014, (impala (-1.3 %), greater kudu (-3.9 %), sable (-2.6 %)) possibly due to diet quality and loss of genetic variability in these populations. However, trophy size for greater kudu and sable were within the minimum score range of the Safari Club International. We recommend research on genetic variability and inbreeding levels of hunted populations in closed ecosystems to inform adaptive management of trophy hunting as a sustainable conservation tool in small isolated parks in Africa.