Effects of resource limitation on habitat usage by the browser guild in Hluhluwe-iMfolozi Park, South Africa

Resource depletion and associated increases in interspecific competition are likely to influence differential habitat usage amongst a guild. We tested some prominent theoretical concepts using observed differences in seasonal habitat use amongst the savanna browser guild (elephant, giraffe, impala, kudu and nyala) in Hluhluwe- iMfoloziPark,South Africa. Herbivorelocations (n =3108)were recordedover 2y usingrepeated roadtransectsand, for elephant, GPS collars (187254 downloads). Densities were calculated using a novel GIS approach designed to be a cost-effectivemethodforannualcensuses,butalsoabletocopewithabruptchangesinvisibility.Selectivityfor(Manly's α)vegetationtypes,andoverlap(Schoener'sindex)invegetationtypeusagewerecalculated.Resourcedepletioninthe dry season resulted in all members of the guild increasing selectivity for vegetation types (sumof absolute values away fromtheneutralvalueforManly'salphafortheguild:dryseasons3.97,5.16;correspondingwetseasons3.12,3.68), but decreasing interspecific overlap (80% of Schoener's indices lower in dry season versus wet season). These effects were more marked over the second, more severe, dry season. We found support for the niche overlap hypothesis and thenichecompressionhypothesis.TheJarman-Bellprinciplewasgenerallysupported,althoughunexpectedlyduring the severe dry season elephant showed the most selectivity for vegetation type. The greater the resource depletion, the morerelevantinterspecificdifferences inhabitatusagebecomeinrelationtothedifferentialimpacts ofguildmembers.