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

Abstract

Density and survival of a raccoon (Procyon lotor) population in Rock Creek Park, an urban national park inWashington, D.C., were estimated using mark–recapture and radio-tracking over an 8-year period following the appearance ofthe mid-Atlantic States (Mid-Atlantic) rabies epizootic. Raccoon density ranged from 333.3 to 66.7/km2 , with an overall parkestimate of 125/km2 . This density places the Rock Creek population within the range of other urban and suburban populationsand is many times greater than raccoon densities reported from other habitats. Density was particularly high in one thin spur ofparkland with the smallest ratio of area to urban edge. Raccoon survival rates were high except among juveniles during therabies epizootic. Data on rabies prevalence from Washington, D.C., indicate a cycle with peaks in 1983 during the initialepizootic and again in 1987 and 1991, a pattern similar to that seen in other carnivores and in rabies models. We found evidenceof 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 raccoonpopulations, urban and suburban populations and protected populations may frequently be subject to epizootics of diseasessuch as canine distemper and rabies, even years after initial contact with a disease.