|Author(s)||Christopher A. J. O’Kane, Kevin J. Duffy, Bruce R. Page and David W. Macdonald|
|Journal||Journal of Tropical Ecology|
Resource depletion and association increases in interspecific competition are likely to influence differential habitat usage amongst a guild. We tested some prominent theoretical concepts using observed differenced in seasonal habitat use amongst the savannah browser guild (elephant, giraffe, impala, kudu and nyala) in Hluhluwe-iMfolozi Park, South Africa. Herbivore locations (n= 3108) were recorded over 2 y using repeated road transects and, for elephant, GPS collars (187254 downloads). Densities were calculated using a novel GIS approach designed to be a cost-effective method for annual censuses, but also able to cope with abrupt changes in visibility. Selectivity for (Manly's alpha) vegetation types, and overlap (Schoener's index) in vegetation type usage were calculated. Resource depletion in the dry season resulted in all members of the guild increasing selectivity for vegetation types (sum of absolute values away from the neutral value for Manly's alpha for the guild: dry seasons 3.97; corresponding wet seasons 3.12, 3.68), but decreasing inerspecific overlap (80% of Schoener's indicies 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 the niche compression hypothesis. The Jarman-Bell principle was generally supported, although unexpectedly during the severe dry season elephant showed the most selectivity for vegetation type. The greater the resource depletion, the more relevant interspecific differences in habitat useage become in relation to the differential impacts of guild members.
Key Words: browsers, competition, elephant, giraffe, GIS, impala, kudu, niche, nyala, savannah, selectivity
Authors: Christopher A. J. O’Kane, Kevin J. Duffy, Bruce R. Page and David W. Macdonald
Journal: Journal of Tropical Ecology
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