Zebra (Equus quagga) social rank and intestinal parasites aggregation

One of the key feature of the ecology of host-parasite relationship is macroparasite aggregation within host population, with most individuals harbouring low numbers of parasites and few individuals playing host to many. The actual effect of parasites in host population dynamic is related to the degree of aggregation but also the category of hosts in which parasites aggregate is important. If parasites aggregate in mating animals the impact on the host’s reproductive number should be higher. Equus quagga lives in multi-level societies. Females live in closed groups, called harems, with their offspring and a single male. A dominant female in harems is recognizable, such as a dominant stallion. The aim of this study was to evaluate the relation between the social hierarchy of E. quagga and the level of parasitism. Individual faecal samples from 141 zebras were collected within the two major populations of E.quagga of Uganda (Lake Mburo Conservation Area and Kidepo Valley National Park). Quantitative (eggs per gram of faeces) parasite assessment were performed with standard methods. The relationship between parasite burden and individual host features was analyzed using Generalised Linear Models. The main result of the present study was the evidence that social status influences parasite level with dominant zebras shedding less parasite eggs than subordinate ones. Social rank appears, therefore, as an important factor giving rise to parasite aggregation in zebras.