Use of warm-season food plots by white-tailed deer

We tested the hypothesis that intensity of use of warm-season food plots by white-tailed deer (Odocoileus virginianus) increases with decreasing nutritional quality and quantity of vegetation in the surrounding habitat. Relative track density (%) in 3-m-wide avenues surrounding each food plot (n = 4) and percent of food-plot forages in feces (determined by microhistological analysis) were determined during June, August, and October 1992 and 1993. Nutritional carrying capacity of the food plots (FCC) and habitat (HCC; deer days/ha) was estimated by multiplying available forage (kg/ha) by digestible energy of the forage (kcal/g) and dividing the product by the daily digestible energy requirement of a 60 kg deer (kcal/deer day). Relative track density (%) and percent of food-plot forages in feces collected within 13-ha sites consisting of food plots and the surrounding habitat were more strongly related to FCC (R 2 = 0.39, P = 0.006 and R 2 = 0.47, P < 0.001; n = 24 [6 sampling dates X 4 food plots]) than to HCC (R 2 = 0.24, P = 0.055 and R 2 = 0.10, P = 0.354). Deer feces collected in 13-ha sites (n = 4) 1 km from each food plot contained less food-plot forage (P < 0.05), more browse (P < 0.05) and cacti (P = 0.016), and similar (P = 0.456) native forbs than feces collected within 13-ha sites (n = 4) centered on each food plot. Intensity of use of food plots was related to standing crop and nutritional quality of food plot forages, however, variation in intensity of use of food plots was explained only partly by variation in FCC and HCC. Because food plot forages did not replace native forbs in deer diets, the use of food plots to artificially increase carrying capacity might result in excessive use of native forbs.