Seasonal habitat use and browsing by deer in Caledonian pinewoods

Abstract

The effects of browsing by deer on the regeneration of native Caledonian pinewoods were studied at two contrasting sites in the Highlands of Scotland: one with high winter use by red deer ( Cervus elaphus), where regeneration of Scots pine ( Pinus sylvestris) had been prevented by browsing, and one with lower use by red deer all year and roe deer ( Capreolus capreolus) also present, where regeneration had been suppressed. The principal aims were to examine the effects of habitat characteristics on the level of use by deer, and to test whether browsing of pine saplings and ground vegetation was related to habitat use by deer. Use of the sites by deer was estimated from dung pellet group density. A novel method for estimating the accumulation period of dung was developed, in which pellet group counts on paired plots, one of which was cleared, were compared. Habitat use by deer during winter and summer was related to topographical characteristics and ground vegetation cover. During winter at the high use site, red deer made greater use of lower altitude, more sheltered plots with a higher cover of heather ( Calluna vulgaris) and blaeberry ( Vaccinium myrtillus), and less use of open, higher altitude plots dominated by wet heath. Habitat use by both deer species in summer and winter was much more evenly distributed across the lower use site, although there was an indication that roe deer might have favoured areas with greatest availability of pine sapling browse and blaeberry during summer. Seasonal differences in the incidence of browsing to pine saplings were observed at both sites. At the high use site, browsing incidence during winter could not be related to herbivore use at the plot scale. Browsing of the much larger pine saplings at the lower use site was heavier in summer than in winter. Leading shoots of saplings about 1 m tall were likely to be damaged in summer. Spatial variation in the annual utilisation of heather was related to deer use at both sites.