Risk of contact between endangered African wild dogs Lycaon pictus and domestic dogs: opportunities for pathogen transmission.
Infectious diseases seriously threaten the populations of many endangered mammals, including African wild dogs Lycaon pictus. Extinction risks may be particularly high where the endangered host lives alongside a more abundant host species which can maintain infection with virulent pathogens. Domestic dogs Canis familiaris are often assumed to act as such 'reservoir hosts' for pathogens threatening wild dogs. We present the first empirical study of contact within and between populations of sympatric wild dogs and domestic dogs. We studied the densities and movement patterns of both species in a Kenyan rangeland, using Global Positioning System-collars and conventional radiotelemetry. Wild dogs lived at low population densities, and direct encounters between packs were rare. In contrast, domestic dogs lived at higher densities and encountered one another more frequently. These differences suggest that directly transmitted virulent pathogens would be more likely to persist within populations of domestic dogs than within wild dog populations. However, wild dog populations alone might maintain pathogens that are indirectly transmitted through vectors or environmental persistence. The risk of contact between the two host species was limited by their behaviour: domestic dogs were associated with human settlements, which wild dogs avoided. Clustering of settlements, reflecting grazing traditions of local pastoralists, accentuated these patterns. We predict that, in this landscape, spillover of directly transmitted pathogens from domestic dogs to wild dogs might be infrequent and rarely followed by onward transmission to other wild dog packs. This may explain the recent growth of the local wild dog population despite sporadic cases of rabies. Synthesis and applications. In this study area, the behaviour of wild and domestic dogs, combined with local land use practices, appeared to limit interspecific disease transmission and hence promote the recovery of the African wild dog population. However, different patterns may occur elsewhere. Moreover, land use changes like those occurring in other African rangelands would undermine such conservation benefits.