Spatial distribution of Serengeti wildebeest in relation to resources

We investigated the spatial distribution of radio-marked wildebeest (Connoc haetes taurinus) in the Serengeti ecosystem in relation to the distribution of their food resources, comparing patterns in the wet and dry seasons and at local and landscape spatial scales. A mechanistic model of ruminant ene rgy optimization predicted that wildebeest should maximize energy intake on swards 3 cm high and maintain energy balance on swards between 3 and 10 cm high. At the ecosystem scale, wildebeest preferred short and intermediate- height grass of moderate greenness during both the wet and dry seasons. Thi s was consistent with the model prediction which suggests that large-scale movements by wildebeest are motivated, at least partially, by an energy-max imizing strategy. At the local scale, however, wildebeest showed spatial se lectivity only on the basis of grass greenness, not on grass height. This d iffered from model expectations and may have resulted from wildebeest explo iting ephemeral green flushes of grass caused by localized rainfall in thei r movement radius. According to these results, the influence of other nutri tional or behavioural factors on wildebeest distributions is not rejected, yet they suggest the potentially important role of an energy intake maximiz ing strategy on movement patterns. Our findings show that wildebeest moveme nts are broadly similar to those of other large herbivores that migrate in response to resource gradients.