Habitat, Group Size, and the Behaviour of White-Tailed Deer

The behaviour of white-tailed deer on Ossabaw Island, Georgia was examined in three habitats which differed in cover density and forage abundance. Forest had relatively dense cover but low forage availability; wooded pasture had relatively dense cover and abundant forage; open pasture had no woody cover but abundant forage. Deer groups were small in both the forest and the wooded pasture relative to groups in the open pasture. Group size in the open pasture did not vary with seasonal changes in forage supply. Groups were small in open pasture during the autumn rut when food was abundant, but were relatively large at other times of year, even during the winter when forage abundance was comparable to that in the forest. Deer in the open pasture spent more time feeding, less time moving, and less time alert than did deer in the forest. Deer in the wooded pasture were intermediate between deer in the other two habitats for percent time feeding, more similar to deer in the open pasture for percent time moving, and more like deer in the forest for percent time alert. Differences in alert behaviour suggest that deer in dense vegetation (e.g. forest and wooded pasture) were more wary than deer in open areas. In all habitats, deer in larger groups (four or more deer) spent more time feeding and less time alert than deer in smaller groups. More aggressive interactions were seen in the open pasture; more nonaggressive interactions were seen in the forest. The rate of aggressive interaction was not clearly related to group size. Temporal variation in nearest-neighbor distance within groups was greater in the forest than in the open pasture, possibly due to loss of contact between deer under conditions of restricted visibility. Although these data suggest that cover density rather than forage characteristics was related to deer group size, no support was given for the hypothesis that this relationship was a consequence of different anti-predator strategies. Groups may have been smaller in dense vegetation because deer had difficulty maintaining contact with other group members when visibility was restricted.