14 research outputs found
Hazel Dormouse ecology and conservation in woodlands
The extent and quality of forested habitats have changed across Europe and as a result many forest species have suffered declines and range contractions. European legislation has been introduced to conserve those species that have been negatively impacted by widespread land-use changes. In order to assess the needs of declining species and the efficacy of these protective measures, the effects of habitat type, configuration and management on individuals and populations needs to be understood.
In this thesis, I have investigated patterns and drivers of variation in the status of populations of hazel dormouse Muscardinus avellanarius in the United Kingdom. I have assessed the effects of variation in habitat on hazel dormice at multiple spatial scales, and related this to woodland management.Natural Environment Research CouncilForestry Commissio
Evaluating Bayesian stable isotope mixing models of wild animal diet and the effects of trophic discrimination factors and informative priors
Funding information University of Exeter; CONICYT, Grant/ Award Number: 3190800; ERC, Grant/ Award Number: 310820Peer reviewedPublisher PD
Associations between abundances of free-roaming gamebirds and common buzzards Buteo buteo are not driven by consumption of gamebirds in the buzzard breeding season
Releasing gamebirds in large numbers for sport shooting may directly or indirectly influence the abundance, distribution and population dynamics of native wildlife. The abundances of generalist predators have been positively associated with the abundance of gamebirds. These relationships have implications for prey populations, with the potential for indirect impacts of gamebird releases on wider biodiversity. To understand the basis of these associations, we investigated variation in territory size, prey provisioning to chicks, and breeding success of common buzzards Buteo buteo, and associations with variation in the abundances of free- roaming gamebirds, primarily pheasants Phasianus colchicus, and of rabbits Oryctolagus cuniculus and field voles Microtus agrestis, as important prey for buzzards. The relative abundance of game-birds, but not those of rabbits or voles, was weakly but positively correlated with our index of buzzard territory size. Gamebirds were rarely brought to the nest. Rabbits and voles, and not gamebirds, were provisioned to chicks in proportion to their relative abundance. The number of buzzard chicks increased with provisioning rates of rabbits, in terms of both provisioning frequency and biomass, but not with provisioning rates for gamebirds or voles. Associations between the abundances of buzzards and gamebirds may not be a consequence of the greater availability of gamebirds as prey during the buzzard breeding season. Instead, the association may arise either from habitat or predator management leading to higher densities of alternative prey (in this instance, rabbits), or from greater availability of gamebirds as prey or carrion during the autumn and winter shooting season. The interactions between gamebird releases and associated practices of predator control and shooting itself require better understanding to more effectively intervene in any one aspect of this complex social-ecological system
Evaluating Bayesian stable isotope mixing models of wild animal diet and the effects of trophic discrimination factors and informative priors
1. Ecologists quantify animal diets using direct and indirect methods, including analysis of faeces, pellets, prey items and gut contents. For stable isotope analyses of diet, Bayesian stable isotope mixing models (BSIMMs) are increasingly used to infer the relative importance of food sources to consumers. Although a powerful approach, it has been hard to test BSIMM performance for wild animals because precise, direct dietary data are difficult to collect.2. We evaluated the performance of BSIMMs in quantifying animal diets when using δ13C and δ15N stable isotope ratios from the feathers and red blood cells of common buzzard Buteo buteo chicks. We analysed mixing model outcomes with various trophic discrimination factors (TDFs), with and without informative priors, and compared these to direct observations of prey provisioned to chicks by adults at nests, using remote cameras.3. Although BSIMMs with different TDFs varied markedly in their performance, the statistical package SIDER generated TDFs for both feathers and blood that resulted in model outputs that accorded well with direct observations of prey provisioning. Using feather TDFs derived from captive peregrines Falco peregrinus resulted in estimates of diet composition that were also similar to provisioned prey, although blood TDFs from the same study performed poorly. The inclusion of informative priors, based on conventional analysis of pellet and prey remains, markedly reduced model performance.4. BSIMMs can provide accurate assessments of diet in wild animals. TDF estimates from the SIDER package performed well. The inclusion of informative priors from conventional methods in Bayesian mixing models can transfer biases into model outcomes, leading to erroneous results. <br/
Climate, landscape, habitat, and woodland management associations with hazel dormouse Muscardinus avellanarius population status
Although strictly protected, populations of the hazel dormouse Muscardinus avellanarius in the UK declined by 72% from 1993 to 2014. Using National Dormouse Monitoring Programme data from 300 sites throughout England and Wales, we investigated variation in hazel dormouse population status (expressed as Indices of Abundance, Breeding, and population Trend) in relation to climate, landscape, habitat, and woodland management. Dormice were more abundant and produced more litters on sites with warmer, sunnier springs, summers, and autumns. Dormouse abundance was also higher on sites with consistently cold local climate in winter. Habitat connectivity, woodland species composition, and active site management were all correlated with greater dormouse abundance and breeding. Abundances were also higher on sites with successional habitats, whereas the abundance of early successional bramble Rubus fruticosus habitat, woodland area, and landscape connectivity were important for population stability. Diversity in the structure of woodlands in Europe has decreased over the last 100 years, and the habitats we found to be associated with more favourable dormouse status have also been in decline. The conservation status of the hazel dormouse, and that of woodland birds and butterflies, may benefit from reinstatement or increased frequency of management practices, such as coppicing and glade management, that maintain successional and diverse habitats within woodland
A brief introduction to mixed effects modelling and multi-model inference in ecology
Acknowledgements This paper is the result of a University of Exeter workshop on best practice for the application of mixed effects models and model selection in ecological studies Funding Xavier A. Harrison was funded by an Institute of Zoology Research Fellowship. David Fisher was funded by NERC studentship NE/H02249X/1. Lynda Donaldson was funded by NERC studentship NE/L501669/1. Beth S. Robinson was funded by the University of Exeter and the Animal and Plant Health Agency as part of âWildlife Research Co-Operativeâ. Maria Correa-Cano was funded by CONACYT (The Mexican National Council for Science and Technology) and SEP (The Mexican Ministry of Education). Cecily Goodwin was funded by the Forestry Commission and NERC studentship NE/L501669/1. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD
Shifting baselines for species in chronic decline and assessment of conservation status. Are hazel dormice Muscardinus avellanarius endangered?
â˘1. Long-term data are beneficial for monitoring the conservation status of species. Assessments of population change over recent periods of fixed duration will, however, be subject to âshifting baselinesâ, where the accepted norm for the population at the start of the period already represents a reduction from historical levels. International Union for Conservation of Nature Red List criteria for categorizing conservation threat rely on assessing declines against quantitative thresholds, generally measured over 10âyears, as indications of the likelihood of extinction in the near future. By contrast, legal frameworks such as the European Habitats Directive require states to achieve and sustain âFavourable Conservation Statusâ for protected species, while domestic conservation legislation can have more diverse objectives and mechanisms, based on local contexts that extend beyond biological or quantitative criteria.
â˘2. We explore the challenges associated with assessing the risk of extinction and the conservation status that arise from the availability of long-term monitoring data for hazel dormice Muscardinus avellanarius in the United Kingdom.
â˘3. Numbers of adult dormice counted in the National Dormouse Monitoring Programme are in ongoing decline, amounting to an overall decline of 78% (95% confidence interval = 72%â84%) over 27âyears, 1994â2020. If the observed annual rate of decline of 5.7% (95% CI = 4.7%â6.8%) were to continue unabated, dormouse counts would decline by >90% from 1994 to 2034. Despite this, the species would never be categorized as Endangered, under IUCN criteria, which specify a reduction of >50% within 10âyears.
â˘4. While such chronic decline may not indicate imminent risk of extinction, justifying a higher Red List category, it is a demonstration of unfavourable conservation status at a national scale. Prioritization based on demonstration of such chronic declines might direct more effective action towards species conservation at a point when their recovery is more attainable, rather than attempting later to reverse a journey to the brink of extinction when the species is finally âEndangeredâ
Identifying pathways to more sustainable farming using archetypes and multi-objective optimisation
The benchmarking of farm environmental sustainability and the monitoring of progress towards more sustainable farming systems is made difficult by the need to aggregate multiple indicators at the relevant spatial scales. We present a novel framework for identifying alternative pathways to improve environmental sustainability in farming systems that addresses this challenge by analysing the co-variance of indicators within a landscape context. A set of sustainability indicators was analysed within the framework of a published set of Farm Management Archetypes (FMAs) that maps the distribution of farming systems in England based on combinations of environmental and management variables. The archetype approach acknowledges that sustainability indicators do not vary independently and that there are regional constraints to potential trajectories of change. Using Pareto Optimisation, we identified optimal combinations of sustainability indicators (âPareto nodesâ) for each FMA independently, and across all FMAs. The relative sustainability of the archetypes with respect to one another was compared based on the proportion of Pareto nodes in each FMA. Potential for improvement in sustainability was derived from distances to the nearest Pareto node (either within or across FMAs), incorporating the cost of transitioning to another archetype based on the similarity of its environmental variables. The indicators with the greatest potential to improve sustainability within archetypes (and, therefore, should have a greater emphasis in guiding management decisions) varied between FMAs. Relatively unsustainable FMAs were identified that also had limited potential to increase within archetype sustainability, indicating regions where more fundamental system changes may be required. The FMA representing the most intensive system of arable production, although relatively unsustainable when compared to all other archetypes, had the greatest internal potential for improvement without transitioning to a different farming system. In contrast, the intensive horticulture FMA had limited internal potential to improve sustainability. The FMAs with the greatest potential for system change as a viable pathway to improved sustainability were dairy, beef and sheep, and rough grazing, moving towards more mixed systems incorporating arable. Geographically, these transitions were concentrated in the west of England, introducing diversity into otherwise homogenous landscapes. Our method allows for an assessment of the potential to improve sustainability across spatial scales, is flexible relative to the choice of sustainability indicators, andâbeing data-drivenâavoids the subjectivity of indicator weightings. The results allow decision makers to explore the opportunity space for beneficial change in a target landscape based on the indicators with most potential to improve sustainability
When is a dormouse âEndangeredâ? Continued population decline of Hazel Dormice (Muscardinus avellanarius) in Great Britain. (Poster)
It is important to monitor species populations to identify changes in Red List assessment, whether increases from conservation or continued declines. This can be more difficult when there are multiple modelling options available. Using data from the National Dormouse Monitoring Programme, provided by the Peopleâs Trust for Endangered Species, we explore the change in British Hazel Dormice (Muscardinus avellanarius) populations using two appropriate generalised additive models. The first uses the negative binomial distribution, and second the Poisson distribution, with a fixed effect of month included. Both models indicate that dormice have declined by >70% between 1994 and 2018 in Great Britain, indicating a continuation of the chronic decline of the species. Our models do not differ significantly in their evaluation of the population trend, but do indicate different Red List categories, leading us to ask: when is the dormouse population considered âendangeredâ