White-Tailed Deer Management Study: Fire Island National Seashore

O'Connell, Allan; Sayre, Mark

White-tailed deer (Odocoileus virginianus) were studied on Fire Island, New York, between 1983 and 1988 to determine population size and dynamics, physical condition, food habits, evaluate the status of Lyme disease, and examine management options. Deer were captured, blood samples and parasites collected, and deer were instrumented with radio collars. Tissues and rumen were collected from carcasses to evaluate physical condition and dietary preferences. Population estimtes and trends were calculated using aerial counts, mark and recapture methods, and winter mortality surveys. Exclosures were constructed to measure deer effects on plant regeneration. Deer densities increased from 12 to 25 dear/sq. km. between 1983 and 1988. Deer increased faster on the western half of Fire Island which contains numerous residential communities than among undeveloped park areas on the Island's eastern half. This was due to lower deer densities, vegetation diversity, and supplemental feedings. Deer exhibited home range fidelity and utilized small ranges throughout the year. Dispersal was observed primarily in males responding to social dominance. Winter mortality in deer following hurricane Gloria (September 1985) increased substantially compared to previous years. This was attributed to an increasing deer population and Gloria's effect on vegetation. Differences in serum urea nitrogen (p=0.05) and trends in other blood characters indicated that winter undernutrition following Gloria was more advanced in fawns from extensive park areas than fawns among residential communities. Thirty-one plant species were identified in rumen analyses, and conifers were common even during summer. Northern deer ticks (Ixodes dammini) were widespread along Fire Island. Thus, deer dispersal may serve to distribute and maintain this tick species. The etiologic agent for lyme disease, Borrelia burgdorferi, was found in 26% of all ticks collected from deer. This spirochete was found in both lone star (Amblyomma americanum) and deer ticks. Positive antibody titers to B. burgdorferi were found in 68% of the deer sampled (n=42). Serial blood samples suggested that re-exposure to adult ticks carrying B. burgdorferi may increase antibody levels. Enzyme Linked Immunosorbent Assays were highly correlated to Indirect Immunofluoresence Assays and were determined efficient in detecting antibody levels to B. burgdorferi in deer sera. While Fire Island deer management will ultimately depend on National Park Service objectives for the area, the current deer population is a product of man's manipulation of the surrounding environments. This intervention should be carefully considered when formulating a deer management plan.