Species differences in exhibit use by antelope: addax (Addax nasomaculatus) and sable (Hippotragus niger)

Abstract

Some conservation breeding centres provide semi-natural conditions for hoofstock herds, to achieve the goal of maintaining genetic and behavioural resilience suitable for eventual reintroduction of conservation-reliant species. Little is known about mixed-species grazing by allopatric herbivores outside their native ranges (ex situ), although species and breed differences have been documented for domestic livestock as well as for sympatric wildlife species. The grazing and resting activities of two species of horse antelope (Hippotraginae) were examined in a central Texas ecoregion characterised by wooded and open grass patches. Theoretically, the mesic-adapted sable antelope Hippotragus niger, would prefer high productivity patches more than the desert-adapted addax Addax nasomaculatus. At three times of the day, behavioural activity and locations of sable (n=28) and addax (n=37) relative to three types of vegetation patches were recorded. It was predicted that sable would more likely (1) forage in locations with higher biomass and (2) rest in shade during midday. Ranked by decreasing forage biomass, the vegetation patch types included introduced exotic grass species (improved), forbs and grasses (native), and woody shrubs or trees (juniper). Shade was greatest in the juniper patches, and temperature was highest during midday. Sable were more likely to be in improved patches (overall and while foraging) and addax were more likely located in native patches. Both species rested in shady juniper patches, primarily during morning and midday. Based on hierarchical analyses using logistic regression models, individual use of patch types was a complex interaction of species, time of day and activity. Use of patches changed significantly during the day, species used patches differently, and foraging behaviour differed among the patches. Better understanding of species differences in use of an ex-situ landscape can contribute to maintaining herd health and behavioural resilience, as needed to meet goals of in-situ population restoration.