Nutritional Condition of White-Tailed Deer in the Central Black Hills, South Dakota: Influence of Habitat and Elk Competition

Research conducted since the middle l 970's has determined that the white-tailed deer (Odocoileus virginianus) population has been decreasing in the central Black Hills (CBH) (Griffin et. al. 1 992, Griffm 1 994, DePemo 1 998). Decline in the deer population may be due to a reduction in habitat quality. Because habitat and nutrition are interrelated, a two-year study was begun in May 1994 to determine the physical and nutritional condition of white-tailed deer occupying five winter study areas, and on summer and winter ranges. Habitat variables, deer diet composition and quality, and nutritional condition were compared between the northern Black H ills (NB H) and the CBH. Also, elk diet composition and quality, and dietary overlap between elk and deer was determined. Habitat variables were measured at 1,241 random locations on each study area and on seasonal ranges. Deer and elk fecal pellet groups were collected at two-week intervals during June-August of 1994 and 1995, and January-March of 1995 and 1996. Fecal nitrogen and fecal phosphorus were used to assess diet quality. Microhistological analysis was used to determine diet composition. Deer nutritional condition was evaluated using ten morphological/physiological and seven blood indices. Diet composition varied among winter study areas and between seasonal ranges. Ponderosa pine (Pinus ponderosa) was the most consumed winter forage and buffaloberry (Shepherdia canadensis) was the most consumed summer shrub by deer. Overall deer diet variation was limited on the CBH winter range. During the winters of 1995 and 1996, fecal nitrogen followed expected intraseasonal trends that were related to intermittent snow cover. More diverse forage types on deer summer range increased the utility of fecal indices to measure diet quality; increased fecal nitrogen and fecal phosphorus levels reflected summer deer diet composition. Generalistic elk food habits show adaptability to successional changes in the CBH forest environment. Deer and elk dietary overlap is ≤ 50% in the CBH, and increased in the winter due to a limited selection of preferred forages by both species. Natural CBH deer forages do not support large deer numbers, and the current population exhibits low body weights and low reproductive rate. NBH deer are characterized in better nutritional condition than CBH deer because of food supplementation and agricultural land availability which support higher deer densities.