Effects of human disturbance on the diet composition of wild red deer (Cervus elaphus)

Disturbance from human recreational activities may affect the nutrition of free-ranging herbivores due to trade-offs between feeding in preferred habitats and perceived predation risk. To test this hypothesis, we estimated diet composition for red deer in the Scottish highlands in spring, when recreational activity tends to be high, and in winter when it is lower. We analysed faecal samples from three habitat types (grassland, heather moorland and woodland) collected at sites close to a busy track (disturbed) and at a distance from it (less disturbed). The diet consisted of 39% grasses, sedges, herbs and rushes (GSHR) and 58% Calluna vulgaris and Erica spp. (heather) in spring, compared with 14% grasses and 77% heather in winter, with small quantities of Vaccinium spp. (berry) and Pinus sylvestris (tree) in both seasons. In spring, faeces from disturbed grass and woodland sites indicated a diet with less GSHR and more heather and tree than faeces from less-disturbed sites, which could be due to an increased need for vigilance in exposed grassland and the need to seek cover. In contrast, faeces from all disturbed sites in winter indicated a diet with more GSHR and less heather than faeces from less-disturbed sites. This could be due to a seasonal decline in recreation and increase in hunting activity reversing the disturbance levels at the different sites, since hunting is not normally carried out in areas used by the public for recreation. We conclude that there may be nutritional benefits to deer of reducing disturbance near open grassland.