Dung Avoidance in Zebra: The Trade-off between Nutritional Advantages and Parasitic Risks

Abstract

The purpose of this study was to determine if Grevy’s (Equus greyyi) or plains (Equus quagga) use dung as an avoidance cue to decrease their exposure to gastrointestinal parasites. To understand the adaptive benefits of this behavior, the costs and benefits of grazing near dung were carefully assessed. In short, grazing near dung comes with the cost of increased parasite ingestion, which can reduce the growth, reproduction, and survival of the host; however, grazing near dung can also provide nutritional benefits, since nutrient leaching can promote vegetation quality and quantity. Factors shaping fecal avoidance in zebra may include seasonal variations in the weather, as well as differences in parasite burdens and body size between Grevy’s and plains. Across experiments, vegetation quality and quantity were statistically similar between dung and control plots, which would indicate that the only distinguishing cue between plots was the presence or absence of dung. Overall, zebra did not show an aversion to dung-filled plots; they did not spend less time in dung filled plots; and, they did not bite less in dung-filled plots. Notably, Grevy’s zebra took more bites than expected in infected regions and less bites than expected in uninfected regions, while plains zebra took the expected number of bites in infected and uninfected regions. In summary, the results from this experiment cast doubt on the potential for anti-parasite foraging strategies in zebra. In addition, zebra in dung-filled plots appear to show a preference for grazing near piles of dung.