Cattle compete broadly with grazing and browsing wildlife, but competition is mitigated in the presence of mega-herbivores

Background/Question/Methods

In many savanna ecosystems worldwide, livestock share the landscape and its resources with wildlife. Although interactions between domestic and wild ungulates have been extensively studied, there is still little consensus on the exact nature of these interactions, in part because of the rarity of controlled replicated experiments. Of particular interest is whether livestock facilitate or compete with wildlife and whether this relationship is influenced by seasonality. Since 1995, we have experimentally manipulated the presence and absence of cattle and large wild ungulates in a Kenyan savanna rangeland in order to better understand the nature of competition and coexistence between these two guilds of herbivores. We use semi-permeable fences to exclude or allow different combinations of mega-herbivore wildlife, meso-herbivore wildlife, and cattle. There are 18 plots, representing six herbivore treatments each replicated three times. We estimated herbivore use of each plot by conducting biennial dung surveys along fixed belt transects measuring 4 x 600-m. 

Results/Conclusions

Between March 2002 and November 2012, we conducted a total of 14 surveys and counted 25,138 dung piles. Zebra and cattle dung respectively constituted 35% and 31% of the total dung piles recoded. Overall dung density was 40% higher during the wet season than dry season. Cattle competitively suppressed all the six species of wildlife for which we had sufficient data. Generally, cattle suppressed zebra more during the wet season than dry season. It appears that mega-herbivores ameliorated or even reversed suppression of wildlife by cattle. In the absence of mega-herbivores, cattle reduced wild herbivores’ dung by 40%, whereas in presence of mega-herbivores, the percentage dung density was reduced by only 15%. Our results suggest that mega-herbivores, perhaps through their impact on tree-grass balance, can dampen the suppressive effect of cattle on wild ungulates.