Population density, survival, and rabies in raccoons in an urban national park

Density and survival of a raccoon (Procyon lotor) population in Rock Creek Park, an urban national park in Washington, D.C., were estimated using mark-recapture and radio-tracking over an 8-year period following the appearance of the mid-Atlantic States (Mid-Atlantic) rabies epizootic. Raccoon density ranged from 333.3 to 66.7/km(2), with an overall park estimate of 125/km(2). This density places the Rock Creek population within the range of other urban and suburban populations and is many times greater than raccoon densities reported from other habitats. Density was particularly high in one thin spur of parkland with the smallest ratio of area to urban edge. Raccoon survival rates were high except among juveniles during the rabies epizootic. Data on rabies prevalence from Washington, D.C., indicate a cycle with peaks in 1983 during the initial epizootic and again in 1987 and 1991, a pattern similar to that seen in other carnivores and in rabies models. We found evidence of decreased raccoon density during and after the 1987 rabies resurgence relative to the years following the original epizootic, when rabies prevalence was low. While hunting and trapping represent a major mortality factor for many rural raccoon populations, urban and suburban populations and protected populations may frequently be subject to epizootics of diseases such as canine distemper and rabies, even years after initial contact with a disease.