Assessing deer densities and impacts at the appropriate level for management: a review of methodologies for use beyond the site scale
- 1Population density alone is unlikely to be a good predictor of the impacts of deer on their environment. The assessment of management requirements should therefore be based on assessment of deer impacts, alongside estimates of density.
- 2Both density and impacts need to be monitored at a landscape scale, and there is a need to develop appropriate methodologies that allow managers to consider the current and likely future impact of deer.
- 3The relevant scale for assessment (and management) varies both with deer species and context of impact, but should always encompass at least the estimated biological range of the population of deer present in an area. Some impacts (e.g. deer–vehicle collisions, and risks of disease transmission) may need to be assessed at a wider regional level.
- 4In this review we consider various approaches available for assessing: absolute or relative animal abundance; impacts of ungulates on agriculture, forestry, amenity woodlands and other conservation sites; impacts on public safety (e.g. through road traffic accidents) and on humans or livestock through potential spread of disease.
- 5In each case the advantages and disadvantages of a variety of methods are considered, before recommendations are made for methodologies which are sufficiently accurate, sufficiently robust and sufficiently practical to be favoured in a management context.
- 6To address impacts at the landscape scale requires management policies that integrate information on both positive and negative impacts of deer in order to ensure appropriate and holistic management. We present a decision-support framework suitable for use within the UK, using inputs from a variety of possible impact types to assist managers and forewarn of situations where current management may need to be modified.