Robust tools are needed to prioritise the management of invasive non-native species

1. The need to assess population size and change is central to any population monitoring programme. A range of monitoring techniques is available for deer, but few studies have addressed the performance of these techniques in terms of their accuracy and their power to detect population changes reliably. This study compares the performance of three commonly used techniques to monitor woodland deer populations in terms of their accuracy, precision and statistical power using field data and simulation modelling. 2. Faecal Standing Crop (FSC) was found to provide the most accurate estimates at all deer densities studied, but was outperformed by distance sampling using thermal imaging in terms of precision and statistical power. Faecal Accumulation Rate (FAR) performed worst in terms of precision and statistical power, and was inferior in terms of accuracy to FSC. The accuracy of FAR and distance sampling using thermal imaging was similar. 3. Annual surveying is not the best use of resources, since 10% per annum increases or decreases in a population could not be detected by any of the techniques within a 3‐year time period. Even with the best technique under the most favourable conditions of deer density simulated in this study, a population change could only be detected reliably once the population had increased by 33% or decreased by 27%. In the least favourable conditions, the respective figures were a 380% increase or extinction. 4. All the techniques studied are relatively poor at detecting population change, so their use in practical deer management needs to be treated with caution. The consequences of relying on similar techniques to detect population change for rare species could be severe.

1. It is often stated that wild deer in Great Britain are increasing in range and number. This study presents the first quantified estimate of national range expansion for all six species. From national surveys of deer presence in 10 km squares between 1972 and 2002, the red deer range is estimated to have expanded at a compound rate of 0.3% per year, fallow deer at 1.8%, Chinese water deer at 2.0%, roe deer at 2.3%, Japanese sika at 5.3% and Reeves' muntjac at 8.2%. 2. Each species is expected to expand its range further for the foreseeable future. The most widespread species, roe deer, is predicted to be present within 79% of all 10 km squares in mainland Britain within 10 years. 3. Deer range expansion brings a combination of benefits and costs, and some degree of management is considered necessary to limit both environmental damage and deer suffering.

Human–wildlife conflicts are increasing throughout the world, principally due to a combination of human population growth, increased pressure on land and natural resources and climate change. Many human–wildlife conflicts stem from differences in objectives between various stakeholder groups, especially where the wildlife in question is a resource that can be exploited for economic or cultural benefit, or where the conservation of wildlife is at odds with human population growth or development pressure. Conflicts can be exacerbated by an incomplete understanding of their causes and/or inappropriate intervention measures. Many traditional forms of intervention are also subject to increasing scrutiny and criticism from society. Here, we highlight the potential strategic benefits that can be made by an interdisciplinary approach to human–wildlife conflict situations, by integrating knowledge and understanding across the natural and social sciences. We also stress the potential tactical benefits from combining new approaches to management with more traditional ones. We emphasise the potential contribution of more recent developments in decision-making under conditions of limited data availability and uncertainty. Finally, we recommend that monitoring should play a more prominent role, both in assessing the role of stakeholder engagement in participatory decision-making and in contributing to the evidence base that will allow competing hypotheses about specific systems to be evaluated in an iterative manner.

Aim  Using six free‐living deer species in Great Britain as a case study, we studied biogeographical relationships of ecologically related species composed of both native and introduced species. Location  Great Britain. Methods  We modelled the environmental favourability for the deer species using variables related with spatial location, climate, topography, human disturbances and habitat structure. Favourability values of each pair of native (naturalized)‐introduced species were used to estimate the fuzzy overlap index (FOvI) as a measure of overall similarity between the environmental requirements for the species in Great Britain. The absolute local overlap values (FOvI‐L) were also used to measure the degree to which a given location was favourable simultaneously for each pair of species. We assessed the trends of species favourability across a range defined by the absolute local overlap values and studied the shape of the obtained curves since they informs us about the favourability balance between the studied species. Results  Muntjac and Chinese water deer attained higher favourability values than native species in localities with intermediate values of FOvI‐L (a reduced number in the study area), suggesting that if competitive relationships were established in these localities the introduced deer species may have some advantages over natives. Sika deer only achieved higher values than fallow deer in those localities clearly unfavourable for the naturalized species. Our analyses predicted that fallow deer will be less affected by the introduced deer species than native species. Main conclusions  We developed an approach based on the favourability function to describe biogeographical relationships between species, natives and introduced and to assess from a biogeographical perspective if introduced species could pose a competitive risk to natives. Although the results of present analyses do not conclusively demonstrate competitive exclusion, they provide directional hypotheses that can be tested in experimental field and laboratory studies.