Animals may anticipate and try to avoid, at some costs, physical encounters with other competitors. This may ultimately impact their foraging distribution and intake rates. Such cryptic interference competition is difficult to measure in the field, and extremely little is known at the interspecific level. We tested the hypothesis that smaller species avoid larger ones because of potential costs of interference competition and hence expected them to segregate from larger competitors at the scale of a resource patch. We assessed fine-scale spatial segregation patterns between three African herbivore species (zebra Equus quagga, kudu Tragelaphus strepsiceros and giraffe Giraffa camelopardalis) and a megaherbivore, the African elephant Loxodonta africana, at the scale of water resource patches in the semi-arid ecosystem of Hwange National Park, Zimbabwe. Nine waterholes were monitored every two weeks during the dry season of a drought year, and observational scans of the spatial distribution of all herbivores were performed every 15 min. We developed a methodological approach to analyse such fine-scale spatial data. Elephants increasingly used waterholes as the dry season progressed, as did the probability of co-occurrence and agonistic interaction with elephants for the three study species. All three species segregated from elephants at the beginning of the dry season, suggesting a spatial avoidance of elephants and the existence of costs of being close to them. However, contrarily to our expectations, herbivores did not segregate from elephants the rest of the dry season but tended to increasingly aggregate with elephants as the dry season progressed. We discuss these surprising results and the existence of a trade-off between avoidance of interspecific interference competition and other potential factors such as access to quality water, which may have relative associated costs that change with the time of the year.

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In many semi-arid savanna ecosystems, surface water is scarce and only found in artificially pumped waterholes at the end of the dry season, leading to high large mammal densities and competition. Further, the modification of the physico-chemical characteristics of the drinking water over the dry season (e.g. through faeces accumulation) could enhance competition. Indeed, elephants, considered as key-competitor, and other herbivores by aggregating near the trough where clear water arrives could compete for this resource. We studied the drinking locations of eight herbivore species around pumped waterholes in relation to these water characteristics in Hwange National Park, Zimbabwe. We identified differences of the physico-chemical characteristics of the water in different sections of pumped waterholes at the end of the dry season. Elephants drank the water in or close to the trough, whereas other species drank further in the waterhole, except roan and sable antelopes which were indifferent about where they drank. Interference competition with elephants for the access to water close to the trough was not detected for zebras and kudus. We discuss possible directions for future research to enhance our understanding of waterhole use by herbivores.