Overlap and seasonal shifts in use of woody plant species amongst a guild of savanna browsers
O'Kane CAJ., Duffy KJ., Page BR., MacDonald DW.
To clarify the potential influence of different browsers in the same guild on woody vegetation, dietary overlap and separation between elephant, giraffe, kudu, nyala and impala was assessed in Hluhluwe-iMfolozi Park, South Africa. Woody species browsed, browsing heights, plant-parts browsed and browsing versus grazing were recorded over 2 y by direct observation. We obtained 3068 browse records. Niche breadth (Levins' measure) and overlap (Schoener's index) in species browsed and browsing heights were calculated. Annual and seasonal differences in these measurements, plant-part use and browsing versus grazing were assessed. Elephant utilized the largest number (n = 78) of different woody plant species. Overlap in species browsed was lower between elephant and other browsers than amongst the latter. Seasonal rainfall influenced the range of woody plants utilized, niche breadth in terms of species browsed and browsing versus grazing. Marked resource depletion caused elephant, contrary to theoretical predictions, to narrow niche breadth in terms of species browsed. However, resource depletion rarely had a significant effect on interspecific overlap in species browsed or overlap in browsing heights, on actual browsing heights or plant-parts utilized. A small suite (n = 8) of woody species formed the core diet of all guild members, implying the potential for synergistic impacts by guild members on these species and for competition between populations of different guild members. © Cambridge University Press 2011.