Relation of pine crop damage to species-specific density in a multi-ungulate assemblage

Abstract

Deer management in forest ecosystems requires information on deer densities and impacts to inform culling decisions with a known target density for acceptable damage levels. In multi-ungulate assemblages, managers need knowledge of relative impacts by different species or guilds. In an extensive (195 km2) conifer forest in eastern England, we related Scots pine (Pinus sylvestris) leader damage (% dominant shoots browsed) in 48 restocked stands (1–3 years growth) over multiple years (n = 79 observations) to species-specific annual muntjac (Muntiacus reevesi), roe (Capreolus capreolus), fallow (Dama dama) and “large deer” densities (composite of annual fallow and multi-year mean red deer Cervus elaphus) using generalized mixed effects models. Forest-wide density surface models were calibrated through intensive annual thermal imaging distance transects and local densities around stands resampled within confidence bounds. Models also examined effects of ground vegetation and hare presence (Lepus europaeus). More pine leaders were browsed at higher fallow or large deer densities (22% and 18%, respectively, increased leader damage across inter-quartile range). Leader damage intensity was not influenced by ground vegetation, hares, muntjac (across the range 8.3–41.6 individuals km−2) or roe deer density (1.7–19.4 individuals km−2). To reduce pine crop damage to economically acceptable levels, managers need to reduce fallow deer to a density as low as 0.6 individuals km−2 (CI = 0.06–1.44, which is considered impractical) or reduce combined large deer density to 2.3 (CI = 1.18–3.46) individuals km−2. Reducing muntjac or roe abundance would minimally affect leader damage in this system, but may be important for other tree species. Multi-species deer management requires species-specific understanding of impacts and robust density estimates.