Population ecology of the Blackbeard Island white-tailed deer.

Abstract (English)

Blackbeard Island, a barrier island of about 1180 ha of upland on the Georgia coast, has a dense population (up to 50 deer per 100 ha) of small deer (Odocoileus virginianus nigribarbis). The island provided an unusually favorable situation for deer population study because losses to predation, illegal hunting, automobile accidents, and emigration were almost nil. Complete records existed of numbers of hunters and deer they killed during archery hunts held annually since 1947. We made a case study of the population in an attempt to characterize its dynamics and to determine the interactions and relative importance of nutrition, parasitism and disease, and hunting in regulating deer numbers. We used harvest data and historical records for a 40-year period to analyze population dynamics and relate them to hunting, mast availability, weather and other factors. Also from 1974 through 1977 we examined and obtained specimens from all deer harvested by hunters and an additional 31 deer taken in spring and summer specifically for this study. Organs and rumen samples were taken as needed. We determined weights, antler measurements, kidney fat levels, food habits, chemical composition of the diet, parasite loads, and reproductive status. We found that bfowse was adequate in quantity, but much of it was of low quality, and deer depended greatly on acorns and other mast to meet energy needs. Acorn production, hunting pressure, and harvest interacted to produce cycles in deer abundance. The strong influence of density-independent factors, particularly mast production, made it difficult to monitor and manage this population by traditional approaches. Data on deer condition obtained from specimens taken in the fall reflected more about the size of the acorn crop than about deer density, because acorn availability was the overriding factor in nutrition. Also, manipulation of the harvest to reduce population density and improve deer condition was not as effective as predicted by traditional management theory. The difficulty in population analysis and management was further exacerbated by sampling problems. Despite either-sex harvest of a high percentage (as much as 40%) of the population on Blackbeard Island, sex and age composition of the harvest did not accurately reflect the sex and age structure of the population. Similar conditions occur in other habitats, and these problems may be widespread but not fully appreciated.

Notes (English)