The impact of deer on lowland woodland invertebrates: a review of the evidence and priorities for future research

Abstract

Direct and indirect impacts of deer on invertebrates in lowland deciduous woodland are reviewed with particular reference to Britain. The evidence overwhelmingly indicates that deer grazing and browsing can have a very profound impact throughout the woodland ecosystem, including on invertebrates. Under certain circumstances, deer may be regarded as direct competitors with insect herbivores for plant biomass. However, more usually impacts will be indirect and mediated through changes in the structure, species composition and quality of the vegetation. The capacity of deer browsing activities to alter radically the species composition of the vegetation will have a major effect on the associated community of herbivorous insects. Whilst excessive deer densities will have detrimental effects on woodland biodiversity, including invertebrates, by inhibiting regeneration and removal of the understorey, some browsing will help to create and maintain open areas within woodland and arrest succession in rides and clearings. This will be beneficial for thermophilous insect species and those that require flowers for nectar and pollen. Evidence on how invertebrates respond to the regrowth foliage that is produced after deer damage remains equivocal but is an important question for future research. Deer also have a direct effect on the dung-associated invertebrate fauna that, in turn, provides an important food source at critical times of year for certain bird and bat species. Emphasis is placed on the importance of a multi-trophic approach in future studies of how deer interact with other components of the woodland ecosystem.