Potential for dietary competition between the threatened black-flanked rock-wallaby and sympatric western grey kangaroo

Abstract

An overabundance of western grey kangaroo (Macropus fuliginosus) can detrimentally impact agriculture and compete with threatened fauna for food resources. In Paruna Wildlife Sanctuary, south-western Western Australia, kangaroos are common and widespread. By contrast, the endangered black-flanked rock-wallaby (Petrogale lateralis lateralis) are spatially constrained to rock refuges. We investigated the potential for dietary competition between these two species by measuring the overlap in their diets, spatial overlap in their foraging patches, and comparing their diets with food resource availability. A combination of scat analysis, passive IR camera trapping and vegetation surveys were employed around rock outcrops used by rock-wallabies within the sanctuary. Rock-wallaby diets were dominated by forbs, overlapping 56% with kangaroo diet, which included mostly browse and forbs. Some of their shared preferred food resources were spatially and/or temporally limited, suggesting potential competition for these food plants. There was also a 33% spatial overlap of foraging patches between the two species. The dietary and spatial overlap detected between rock-wallabies and kangaroos suggest there is potential for resource competition, which may be exacerbated if kangaroo numbers increase. Future conservation actions include monitoring western grey kangaroo densities and food plant availability. Population control for kangaroos may be required, particularly for increasingly hot and dry years, as predicted under climate change.