Diets and feeding selectivities of bridled nailtail wallabies and black-striped wallabies

Abstract

Diets and feeding selectivities of sympatric bridled nailtail wallabies, Onychogalea fraenata, and black- striped wallabies, Macropus dorsalis, were studied at two sites during each season on Taunton Scientific Reserve, Queensland. Bridled nailtail wallabies ate a wide variety of monocotyledon and dicotyledon species (>60) in broadly equal proportions. During dry seasons, there was a marked switch to dicotyledons, including woody browse species, which formed over 20% of material in faecal pellets. In contrast, black- striped wallabies were predominantly grazers, eating a wide variety of grasses and sedges (>65 spp.). Compared with black-striped wallabies, bridled nailtail wallabies were much more selective in their feeding, both for individual plant species and plant parts. Bridled nailtail wallabies selected against grass species, particularly during the dry season, and showed high selectivity for forbs in areas where these were scarce. Black-striped wallabies generally selected against forbs and showed random selection for grass species. Bridled nailtail wallabies showed stronger selection for food items of relatively high nutritional value (such as leaves and seedheads), and stronger selection against items of relatively high fibre content (such as grass stems) than did black-striped wallabies. Dietary overlap varied seasonally and was highest during spring and summer. The potential for inter-specific competition was highest during spring, when food resource abundance was lowest. The feeding niche of bridled nailtail wallabies is narrower than that of black-striped wallabies, indicating that the effects of competition may not be symmetric between the wallaby species. The results of this study agree with those of previous work on these species.