Direct and indirect genetic methods of estimating dispersal: Applications for raccoon rabies management

Predictive disease modeling is a useful tool in assessing management actions for cost effective and successful control of wildlife disease. However, contingent on their success is having accurate estimates of important ecological parameters, such as host dispersal. Dispersal will influence the spatial and temporal rate of disease spread; unfortunately dispersal of wildlife is difficult to measure. For raccoons (Procyon lotor) dispersal has been estimated using field based methods with varying success. We present genetic parentage assignment to directly measure offspring dispersal distances and indirect spatial genetic structure analysis as additional approaches in estimating dispersal. We applied these methods on two study areas in Ontario, Niagara (N=295) and St. Lawrence (N=593); these areas are of management concern because they are at the front of a rabies epizootic. We found the majority of raccoons moved only short distances (<3km), while a few showed dispersal distances in excess of 20km. Analysis of spatial genetic structure provided a similar assessment of the dispersal behaviour of raccoons, indicating stronger genetic structure for juveniles than adults, and females exhibiting stronger philopatry than males. Without the inclusion of age class data the spatial genetic analysis could be misinterpreted due to the timing of juvenile dispersal and sample collection. This dispersal information will be used for predictive modeling and management of raccoons and raccoon rabies in Ontario by the Ontario Ministry of Natural Resources.