The social dynamics of the Cape buffalo and the epidemiological implications

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Although the ecology of the Cape buffalo is reasonably well understood, the social dynamics occurring within and among groups are less known, despite the important implications for both buffalo ecology and management, and intra and interspecies disease transmission. This thesis aims to better understand the social behaviour of Cape buffalo across several populations in sub-Saharan Africa using a combination of GPS tracking data and genetic markers. This thesis quantifies the dynamics of interactions within and among neighbouring buffalo groups and examines the influence of seasonality and inter-population variance on these dynamics. I also investigate the influence of sex on the dispersal ability, in order to better understand the spread of pathogens among populations. To go further, I examine the impact of intragroup dynamics on a directly transmitted pathogen spread as a model to link the host social organisation and pathogen transmission. This thesis reveals different social dynamics within and among groups, although consistent among the study populations. Results show that buffalo form relatively distinct groups occupying unique and separated home ranges, with minimal overlap, independently on the season. Direct contacts (i.e. the use of the same space at the same time) among groups were rare while indirect contacts (i.e. the use of the same space at different times or through an intermediate vector, here the mosquito) occurring within one month were more frequent, with serious implications for indirectly transmitted pathogens in the population. These results suggest a behavioural avoidance or a territorial behaviour occurring throughout the year. It appears that both males and females disperse among neighbouring groups, but females could be more likely to disperse among populations than males. Within groups, individuals form very unstable dyadic associations. These fission-fusion dynamics varied seasonally, with fission patterns lasting 1 to 3 days before individuals merge again for an equivalent average duration. However, it seems that the way individuals interact with each other within groups only slightly affects the transmission of a directly transmitted pathogen. This study is one of the first to quantify the degree of fission-fusion dynamics and intergroup encounter in the Cape buffalo, and to relate these dynamics to variations in environmental conditions across several populations. Therefore, this thesis contributes to the understanding of buffalo social systems and their relation to the environment, a growing issue at the wildlife-livestock interfaces given the economic costs due to pathogen transmission with cattle.

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