The mechanisms underlying animal social organization are complex, particularly in those populations with fission-fusion dynamics, in which individuals temporarily associate. Such social system is thought to allow animals to respond and to flexibly balance conflicting demands by frequent changes in group membership and size. Understanding how fission–fusion dynamics influence population structure has important implications such as for pathogen transmission. In African ecosystems, the African buffalo (Syncerus caffer) exhibits fission-fusion dynamics and is an important maintenance host for diseases. It is therefore essential to understand the factors driving temporal association patterns in the species. 

In African buffalo, adult females, a smaller proportion of adult males, sub-adults and young are usually considered to live in herds, called “mixed herds”, of approximately 20 to 2000 individuals. At sexual maturity, males can temporarily leave the herd to form bachelor groups. Mixed herds are dynamic over time and exhibit a complex social structure characterized by fission and fusion events. The drivers of such complex social dynamics have not been widely studied but it seems that they are related to resource availability (water and forage) and social interactions. Between 2008 and 2013, 76 adult buffalos have been equipped with GPS collars in three sites in southern Africa, located in two TransFrontier Conservation Areas (TFCAs): Gonarezhou National Park and Kruger National Park both within the Great Limpopo (GL-TFCA) and Hwange National Park within the KAvango-ZAmbezi (KAZA-TFCA). In this multi-sites study, I have investigated the spatiotemporal patterns of association between and within herds (i.e. fission-fusion patterns) aiming at better understanding the social ecology of the buffalo. In order to assess association patterns, I calculated the seasonal home-range overlap, the time sharing and duration of fusion and fission events between buffalo dyads using radio-tracking data. I then related the locations of fusion and fission events to environmental variables to examine the main ecological factors influencing association patterns. Whilst some individuals exhibited a strong and well-marked spatial segregation, suggesting behavioural avoidance at the inter-herd level, others showed low spatial segregation. Low spatial segregation was however associated with very variable degrees of temporal association between dyads. The findings indicate that the buffalo populations live in groups with spatial segregation and with a high intra-group dynamics (fusion and fission patterns). This study also reports data on the duration of fusion and fission events, which has been little described in the species. This new knowledge regarding the social ecology of the African buffalo is important in order to understand the dynamics of intra- and interspecific disease transmission.

Academic aim: Employ a multidisciplinary approach to a pre-existing dataset to examine the extrinsic and intrinsic factors driving association patterns in the African buffalo and the implications for the risk of pathogen and disease transmission at wildlife/livestock interfaces. 

Objectives: 

1. To redefine the concept of a herd using telemetry data. 

2. To investigate the main ecological and social factors influencing the dynamics of fission-fusion events using GIS, remote sensing and genetic data. 

3. To assess the impact of the wildlife/livestock interfaces on the dynamics of fission-fusion events. 

4. To model the implications of (1), (2) and (3) for pathogen transmission along a gradient of anthropological disturbance.