Grass attributes and seasonal changes in foraging by a preferentially grazing savanna mixed feeder

Abstract

Driven by metabolic requirements, large mammalian herbivores often become more selective to attain high-quality forage during dry times, especially in semi-arid habitats. Our main objective was to investigate which plant characteristics form the major drivers in the forage use of a mixed feeder during the dry season. The study was done in two savanna reserves in South Africa, Manyeleti Game Reserve (Manyeleti) and Wits Rural Facility (WRF), during the dry season from May to October 2009. We observed impala (Aepyceros melampus) and identified the grasses, dicots, and plant parts that they fed on. We recorded greenness, estimated biomass of feeding patches, ranked basal cover of each grass species, and measured the average height of used grasses. We collected fresh faeces to assess diet composition through microhistology. We found that location, season, greenness, basal cover, and height of grass influenced grass use. The probability of using grass increased with an increased in grass height and impala was more likely to use greener grass in the late dry season. We demonstrated that greenness is one of the key drivers in grass use and together with the indirect effect of rainfall play a major role in herbivore forage use in highly seasonal environments.