Abstract:
Many studies on the coexistence of wildlife with livestock have focused primarily on similarsized species. Furthermore, many of these studies have used dietary overlap as a measure
of potential competition between interacting species and thus lack the important link
between dietary overlap and any negative effects on a particular species–a prerequisite for
competition. Consequently, the mechanisms that drive interspecific interactions between
wildlife and cattle are frequently overlooked. To address this, we used an experimental
setup where we leveraged different cattle stocking rates across two seasons to identify the
drivers of interspecific interactions (i.e. competition and facilitation) between smaller-bodied
oribi antelope and cattle. Using direct foraging observations, we assessed dietary overlap
and grass regrowth, and also calculated oribi nutritional intake rates. Ultimately, we found
that cattle compete with, and facilitate, smaller-bodied oribi antelope through bottom-up control. Specifically, cattle facilitated oribi during the wet season, irrespective of cattle stocking
density, because cattle foraging produced high-quality grass regrowth. In contrast, during
the dry season, cattle and oribi did not co-exist in the same areas (i.e. no direct dietary overlap). Despite this, we found that cattle foraging at high densities during the previous wet season reduced the dry season availability of oribi’s preferred grass species. To compensate,
oribi expanded their dry season diet breadth and included less palatable grass species, ultimately reducing their nutritional intake rates. Thus, cattle competed with oribi through a
delayed, across-season habitat modification. We show that differences in body size alone
may not be able to offset competitive interactions between cattle and wildlife. Finally, understanding the mechanisms that drive facilitation and competition are key to promoting coexistence between cattle and wildlife.
Description:
Supporting information: S1 Table. Seasonal mean % crude protein per grass species in different grass greenness categories across low (1.7 ha/AU), intermediate (1.5 ha/AU) and high (0.95 ha/AU) stocking rates at Arundel Farm, Ixopo, South Africa.