A test of five mechanisms of species coexistence between rodents in a southern African savanna
The operation of five different mechanisms of species coexistence in a community of rodents was examined in a semi-arid Kalahari savanna in southern Africa. The two most common species were Tatera leucogaster (bushveld gerbil) and Rhabdomys pumilio(striped mouse). The mechanisms examined were habitat selection in a mosaic, microhabitat selection, spatial variation in resource abundance, temporal variation in resource abundance, and diet partitioning. The rodents were censused using mark-recapture live trapping, activity measured using sand-tracking, and foraging efficiency measured using giving-up densities (GUDs; the amount of food remaining following patch exploitation) in experimental food patches. There was no support for any of the five mechanisms: T. leucogaster tended to be a more efficient and mobile forager than R. pumilio. It is suggested that coexistence maybe based on a sixth mechanism, seasonal variation in resource abundance and a tradeoff of maintenance efficiency versus foraging efficiency. Further, it appears that R. pumilio is more efficient at maintaining harvest potential, not by maintaining high consumer biomass, but rather by having a high intrinsic rate of increase.
Keywords: species coexistence, optimal patch use, giving-up densities, Kalahari desert, Africa, rodents, habitat selection, resource abundance