Scott Newey

Parasite–mediated reduction in fecundity of mountain hares

Mountain hare populations in Scotland exhibit regular 10 year fluctuations in abundance. Simple models of host–parasite population dynamics suggest that parasite–mediated reductions in host fecundity can cause a transition from stable to cyclic host population dynamics. We tested the hypothesis that parasites reduce hare fecundity by experimentally reducing parasite burdens and recording female survival, body condition and fecundity. We captured 41 adult female hares in October 2002; 22 were treated with Ivermectin to remove parasites and 19 were left untreated as controls. The treated and untreated hares were culled in May 2003 together with a second control group of nine unhandled hares. Treatment with Ivermectin significantly reduced the abundance of Trichostrongylus retortaeformis and increased the fecundity of the hares, but had no measurable effect on body condition or over–winter survival. These results are consistent with the hypothesis that parasites may be a contributory cause of cycles in populations of mountain hares.

Can distance sampling and dung plots be used to assess the density of mountain hares Lepus timidus

We evaluated distance sampling and dung plots as cost-effective methods of estimating the density of mountain hares Lepus timidus on moorland in the Scottish Highlands. We compared density estimates derived from these techniques to those derived from labour-intensive capture-recapture techniques. Distance sampling and capture-recapture techniques produced comparable density estimates at medium and low hare densities. Density estimates derived from distance sampling were higher than those derived from capture-recapture in high-density hare populations. Both distance sampling and capture-recapture techniques gave wide confidence intervals at high hare density. Histograms of perpendicular sighting distances showed that a large proportion of hares were seen on or close to the transect line and that there was a rapid fall off in detection rates with distance. This finding indicated that hare behaviour may lead to problematic survey design and may reduce the precision of density estimates. The collection of accurate distance sampling data was particularly problematic when hare density was high. In contrast, in low-density hare populations, considerable sampling effort was required to obtain sufficient sightings of hares to reliably estimate density. Dung plots provided a relative index of abundance that successfully ranked populations of mountain hares in order of increasing density as determined by distance sampling and capture-recapture techniques. With careful study design, distance sampling provides a good compromise between accuracy, precision and effort in estimating the density of mountain hares. The use of dung plots is a rapid alternative when only estimates of relative abundance are required.

Unstable dynamics and population limitation in mountain hares

The regular large‐scale population fluctuations that characterize many species of northern vertebrates have fascinated ecologists since the time of Charles Elton. There is still, however, no clear consensus on what drives these fluctuations. Throughout their circumpolar distribution, mountain hares Lepus timidus show regular and at times dramatic changes in density. There are distinct differences in the nature, amplitude and periodicity of these fluctuations between regions and the reasons for these population fluctuations and the geographic differences remain largely unknown. In this review we synthesize knowledge on the factors that limit or regulate mountain hare populations across their range in an attempt to identify the drivers of unstable dynamics.

Can parasites drive population cycles in mountain hares

Understanding the drivers of population fluctuations is a central goal of ecology. Although well-established theory suggests that parasites can drive cyclic population fluctuations in their hosts, field evidence is lacking. Theory predicts that a parasite that loosely aggregates in the host population and has stronger impact on host fecundity than survival should induce cycling. The helminth Trichostrongylus retortaeformis in the UKs only native lagomorph, the mountain hare, has exactly these properties, and the hares exhibit strong population fluctuations. Here we use a host–parasite model parametrized using the available empirical data to test this superficial concordance between theory and observation. In fact, through an innovative combination of sensitivity and stability analyses, we show that hare population cycles do not seem to be driven by the parasite. Potential limitations in our parametrization and model formulation, together with the possible secondary roles for parasites in determining hare demography, are discussed. Improving our knowledge of leveret biology and the quantification of harvesting emerge as future research priorities. With the growing concern over the present management of mountain hares for disease control in Scotland, understanding their population drivers is an important prerequisite for the effective management of this species.

Carcass Provisioning to Support Scavengers: Evaluating a Controversial Nature Conservation Practice

A number of scavenger species have suffered population declines across Europe. In attempts to reverse their decline, some land and wildlife managers have adopted the practice of leaving or placing out carcasses of wild or domestic herbivores to provide a source of carrion. However, this can be a controversial practice, with as yet unclear outcomes for many target species and the ecosystems they are part of. Here we bring out the key aspects of this increasingly common conservation practice illustrated using three contrasting cases studies. We show that the provision of carcasses is often motivated by a desire to benefit charismatic species or to facilitate nutrient cycling throughout an ecosystem. Evidence for the effectiveness of this practice in achieving these objectives, however, is mostly lacking, with ecologists studying “easier” species groups such as beetles and therefore not providing relevant insights. Moreover, conflicts between environmental policies that carcass provisioning is aimed at and other social and economic objectives do occur but these projects are often designed without taking into account this broader context. We conclude that expecting carcasses to simply be “good for biodiversity” may be too naïve a view. A greater knowledge of the impact of carcass provisioning and placement on ecosystems and society at large is required before it can become a more effective conservation tool at a wider scale.

The strong and the hungry: bias in capture methods for mountain hares Lepus timidus

Abstract Estimating density, age and sex structure of wild populations is a key objective in wildlife management. Live trapping is frequently used to collect data on populations of small and medium-sized mammals. Ideally, sampling mammal populations by live capturing of individuals provides a random and representative sample of the target population. Trapping data may, however, be biased. We used live-capture data from mountain hares Lepus timidus in Scotland to assess sampling bias between two different capture methods. We captured hares using baited cage traps and long nets on five study areas in the Scottish Highlands. After controlling for the effects of body size, individuals caught in traps were lighter than individuals caught using long nets, suggesting that the body condition of hares differed between the capture methods. This tendency may reflect an increased risk-taking of individuals in poorer body condition and less aversion to entering traps in order to benefit from eating bait. Overall, we caught more adult hares than juveniles and more female hares than males. Our results show that estimates of density and population structure of mountain hares using live-capture data could be affected by the capture method used. We suggest that live-capture studies employ more than one capture method and test for heterogeneity in capture probability to minimise potential bias and achieve reliable estimates of population parameters.

Impact of Management on Avian Communities in the Scottish Highlands

The protection of biodiversity is a key national and international policy objective. While protected areas provide one approach, a major challenge lies in understanding how the conservation of biodiversity can be achieved in the context of multiple land management objectives in the wider countryside. Here we analyse metrics of bird diversity in the Scottish uplands in relation to land management types and explore how bird species composition varies in relation to land managed for grazing, hunting and conservation. Birds were surveyed on the heather moorland areas of 26 different landholdings in Scotland. The results indicate that, in relation to dominant management type, the composition of bird species varies but measures of diversity and species richness do not. Intensive management for grouse shooting affects the occurrence, absolute and relative abundance of bird species. While less intensive forms of land management appear to only affect the relative abundance of species, though extensive sheep grazing appears to have little effect on avian community composition. Therefore enhanced biodiversity at the landscape level is likely to be achieved by maintaining heterogeneity in land management among land management units. This result should be taken into account when developing policies that consider how to achieve enhanced biodiversity outside protected areas, in the context of other legitimate land-uses.

Using PIT-Tag Technology to Target Supplementary Feeding Studies

The role of food in limiting or regulating populations of mammalian herbivores remains a central question in ecology with great relevance to wildlife and livestock management. Supplementary feeding studies have been widely used to assess the potentially limiting role of food availability, and supplementary feeding is also a common management technique. In both contexts there is an assumption that all individuals in the target population have access to food. There are, however, questions as to whether supplementary feed reaches the target population and how benefits are translated into individual and population level effects. We describe and use a technique using Passive Induced Transponder (PIT) tags to monitor individual use of supplementary feed in wild mountain hare Lepus timidus populations and test the assumption that supplementary feed reaches the target population. Over the course of one winter only 50% of the target hare population used supplementary feed and there was considerable individual variation in the time spent feeding among those individuals that fed. Neither age, sex nor an index of body condition were significant in explaining which individuals visited feeding stations or how long individuals spent feeding. The method and results described here suggest that, at least for the mountain hare, the central assumption that all target individuals have access to and use supplementary feed is invalid. Great care is thus needed in designing and interpreting the results of supplementary feeding studies or management programmes that include supplementary feeding.

WiseEye: Next Generation Expandable and Programmable Camera Trap Platform for Wildlife Research

The widespread availability of relatively cheap, reliable and easy to use digital camera traps has led to their extensive use for wildlife research, monitoring and public outreach. Users of these units are, however, often frustrated by the limited options for controlling camera functions, the generation of large numbers of images, and the lack of flexibility to suit different research environments and questions. We describe the development of a user-customisable open source camera trap platform named ‘WiseEye’, designed to provide flexible camera trap technology for wildlife researchers. The novel platform is based on a Raspberry Pi single-board computer and compatible peripherals that allow the user to control its functions and performance. We introduce the concept of confirmatory sensing, in which the Passive Infrared triggering is confirmed through other modalities (i.e. radar, pixel change) to reduce the occurrence of false positives images. This concept, together with user-definable metadata, aided identification of spurious images and greatly reduced post-collection processing time. When tested against a commercial camera trap, WiseEye was found to reduce the incidence of false positive images and false negatives across a range of test conditions. WiseEye represents a step-change in camera trap functionality, greatly increasing the value of this technology for wildlife research and conservation management.

Consequences of game bird management for non‐game species in Europe

This work was originally funded by EU Framework IV for the project Reconciling Gamebird Hunting and Biodiversity (REGHAB), and continued under FP7 HUNTing for Sustainability. S.R. is grateful for his King Carl XVI Gustaf guest professorship with SLU, which gave him the time to finish this manuscript. P.B. was supported through the EDP Biodiversity Chair. S.N. and R.J.I. were also supported by the Rural & Environment Science & Analytical Services Division of the Scottish Government.