EFFECT OF DEER EXCLUSION ON THE ABUNDANCE OF IMMATURE IXODES-SCAPULARIS (ACARI, IXODIDAE) PARASITIZING SMALL AND MEDIUM-SIZED MAMMALS

Effects of deer exclusion on abundance of immature Ixodes scapularis S ay parasitizing small and medium-sized mammals, and the role mammals h ave in introducing ticks to exclosure areas, were examined at two site s in Westchester County, New York. In total, 686 mammal captures repre senting nine species were obtained, with white-footed mice, Peromyscus leucopus Rafinesque, composing >80% of all captures, followed by racc oons, Procyon lotor (L.); opossums, Didelphis virginiana (Kerr); and s triped skunks, Mephitis mephitis Schreber. At the Near Archives site, 14% of 81 individual mice, 46% of raccoons, and 33% of opossums captur ed were found to cross the exclosure fence, as did 12% of 50 mice and 38% of raccoons at the Hudson Pines site. Skunks apparently did not cr oss the fence at either site. Mice captured exclusively outside the Ne ar Archives exclosure hosted significantly more larvae than mice captu red inside only, with fence crossers hosting an intermediate number of larvae. At Hudson Pines, numbers of larvae on fence-crossing mice and those captured solely inside the exclosure were equivalent, with tick loads on mice captured outside the exclosure significantly greater. T he number of larvae per raccoon did not differ significantly with capt ure location (inside, outside, or both sides of exclosure fence) at ei ther site. Densities of host-seeking larvae and nymphs were significan tly higher outside the exclosure than inside at Near Archives, though not at Hudson Pines. Differences in tick density inside and outside ex closures declined with each successive developmental stage so that adu lt density inside exclosures tended to converge with that outside at b oth sites. Although deer exclosures can have a significant impact on n ymphal I. scapularis abundance, they may not reduce the risk of encoun tering infected adults. Mice, raccoons, and opossums have a role in in troducing potentially infective ticks to areas where deer have been ex cluded, though the level of immigration of ticks into the area will li kely depend on the density of ticks outside the exclosure.