Dampening prey cycle overrides the impact of climate change on predator population dynamics : a long-term demographic study on tawny owls

Funded by ERA-Net BiodivERsA NERC. Grant Numbers: NE/E010660/1, NE/F021402/1, NE/G002045/1Peer reviewedPublisher PD

Age and sex-selective predation moderate the overall impact of predators

© 2014 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. Acknowledgements: Thanks to J. Reid, S. Redpath, A. Beckerman and an anonymous reviewer for their helpful comments on a previous version of the manuscript. This work was partly funded by a Natural Environment Research Council studentship NE/J500148/1 to SH and a grant NE/F021402/1 to XL and by Natural Research Limited. Forest Research funded all the fieldwork on goshawks, tawny owls and field voles during 1973–1996. We thank B. Little, P. Hotchin, D. Anderson and all field assistants for their help with data collection and Forest Enterprise, T. Dearnley and N. Geddes for allowing and facilitating work in Kielder Forest. In addition, we are grateful to English Nature and the BTO for kindly issuing licences annually visit goshawk nest sites. Data accessibility: All data associated with the study which have not already been given in the text are available from the Dryad Digital Repository: http://doi.org/10.5061/dryad.h1289 (Hoy et al. 2014).Peer reviewedPublisher PD

The UK medical education database (UKMED) what is it?:Why and how might you use it?

The development of UKMED has not been directly funded by but has received support from the General Medical Council and Medical Schools Council as well as staff time from all participating organisations.Peer reviewedPublisher PD

On property benefits of precision livestock management technologies

Precision Livestock Management (PLM) has been identified as an imperative investment area in the northern Beef RD&E Strategy. Precision Livestock Management refers to a range of new technologies and applications with the potential to improve environmental sustainability, productivity, price received, labour and cost efficiency through enhanced measurement, monitoring or management. However, it is still unclear exactly what benefits incorporating these technologies into northern Australian beef enterprises would deliver. Difficulties in defining how emerging technologies could be applied and the lack of quantitative property level data on which to base assumptions about technology costs and benefits contribute to this uncertainty. The project team have been working with five commercial beef producers across northern Australia to identify how six PLM technologies can be applied at the enterprise level. The six technologies considered were: 1) walk over weighing (WOW), 2) auto-drafting, 3) the ePreg system, 4) low resolution spatial animal information, 5) high resolution spatial animal information and 6) remote vegetation sensing. The objectives of the project is to ranked the economic benefits and feasibility of promising PLM technology applications for five northern beef case-study properties and investigate how these might be implemented to measure their impact on the enterprise. The five case study properties will be located in Queensland, the Northern Territory and the Kimberley and Pilbara regions of Western Australia. PLM technologies will be evaluated in relation to the enterprise-operating environment and their potential to increase enterprise operating margin. A complete model of farm production costs and benefits was implemented to evaluate the potential economic impact from PLM technologies. In-depth interviews with case-study property managers were conducted to obtain economic and production data about the current enterprise and provide insights into the expected benefits of selected PLMs. The approach used allows property and regional level differences in potential net benefits of the PLM technologies to be captured. The economic analysis will focus on property-level potential net benefits of the selected PLM technologies using the case studies to inform a farm-business model incorporating risk and uncertainty. The method proposed represents a generalisation of traditional Benefit Cost Analysis (BCA) allowing examination of traditional BCA metrics such as the Internal Rate of Return (IRR), discounted cash flows and the Benefit Cost Ratio (BCR) cash flows, benefit cost analysis, net present value and internal rate of return

Scale invariant spatio-temporal patterns of field vole density

1 Recent characterizations of the spatial scale of population dynamics have typically considered patterns at a single scale and ignored the possibility that different patterns may arise at different scales. In this study we assessed population densities of field voles with cyclic dynamics in northern England at 147 sites from three spatial scales on five occasions over a 2·5‐year period. 2 The scale over which densities were similar was estimated by comparing the variance of density at the three scales (< 1 km2, 10 km2, and 70 km2) and by using autocorrelation techniques. Closer sites were more similar in density than more distant sites and the autocorrelations suggested that sites up to within 8–20 km had more similar densities and higher population synchrony than the average similarity for all the sampling sites. 3 A generalized additive model fitted to all the data showed that the data supported the hypothesis of a travelling wave of vole densities moving through the study area. The model assumed that the wave moved at a constant speed and in a uniform direction. Estimates of the wave’s speed (14 km year−1) and direction (travelling in a direction of 66° from north) were consistent with the estimates which had previously been calculated from a time series of vole densities covering a much smaller spatial area but a longer temporal scale. 4 The spatio‐temporal pattern of vole densities detected over a small spatial scale therefore appears to extend over much larger scales and occurs despite the fragmentation of suitable vole habitat at local (a few square kilometres) and regional (hundreds of square kilometres) scales

Estimated age at death for owl ring recoveries, and recruitment of breeders into the owl population

Data were collected in the field using methods described in the manuscript. No abbreviations used

Data from: Age and sex-selective predation as moderators of the overall impact of predation

Currently, there is no general agreement about the extent to which predators’ impact prey population dynamics, as it is often poorly predicted by predation rates and species abundances. This could in part be caused by variation in the type of selective predation occurring. Notably, if predation is selective on categories of individuals that contribute little to future generations, it may moderate the impact of predation on prey population dynamics. However, despite its prevalence, selective predation has seldom been studied in this context. Using recoveries of ringed tawny owls (Strix aluco) predated by ‘superpredators’, northern goshawks (Accipiter gentilis) as they colonised the area, we investigated the extent to which predation was sex and age-selective. Predation of juvenile owls was disproportionately high. Amongst adults, predation was strongly biased towards females and predation risk appeared to increase with age. This implies age-selective predation may shape the decline in survival with age, observed in tawny owls. To determine whether selective predation can modulate the overall impact of predation, age-based population matrix models were used to simulate the overall impact of five different patterns of age-selective predation, including the pattern actually observed in the study site. The impact on owl population size varied by up to 50%, depending on the pattern of selective predation. The simulation of the observed pattern of predation had a relatively small impact on population size, close to the least harmful scenario, predation on juveniles only. The actual changes in owl population size and structure, observed during goshawk colonisation were also analysed. Owl population size and immigration were unrelated to goshawk abundance. However, goshawk abundance appeared to interact with owl food availability to have a delayed effect on recruitment into the population. This study provides strong evidence to suggest that predation of other predators is both age and sex-selective and that selective predation of individuals with a low reproductive value may mitigate the overall impact of predators on prey population dynamics. Consequently, our results highlight how accounting for the type of selective predation occurring is likely to improve future predictions of the overall impact of predation