Deer abundance estimation at landscape-scales in heterogeneous forests

Waeber, Kristin and Dolman, Paul (2015) Deer abundance estimation at landscape-scales in heterogeneous forests. Basic and Applied Ecology, 16 (7). pp. 610-620.

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    Abstract

    Reliable estimates of deer abundance support effective management of source-sink population dynamics in complex landscapes and improve understanding of the relation between deer density and biodiversity impacts. Performance of distance sampling using thermal imaging of Reeves’ muntjac Muntiacus reevesi and roe deer Capreolus capreolus was examined across 123 km2 of conifer forest in Eastern England, sampling 1567 km in total. For muntjac distance sampling was compared to estimates from drive counts in 2007. For each of three subsequent winters (2008-2010), we compared the magnitude and precision of forest-wide abundance estimated from analytical designs that: i) ignored potential habitat-specific detectability, either with uneven or balanced sampling effort; ii) controlled for sampling effort and/or density among seven forest blocks (mean = 18.8 km2 ± 11.1 SD); iii) accounted for potential movement prior detection; iv) accounted for varying detectability among habitat classes (as a covariate), while controlling for differing densities among blocks. Detectability was further examined in models that stratified to estimate habitat-specific Effective Strip Width (ESW). Estimated muntjac densities from distance sampling were of similar magnitude to estimates from drive counts. Over 2008-2010, we observed 1926 muntjac and 921 roe groups; allowing robust abundance estimation and habitat-specific analysis. ESWs in open habitat were 31% and 27% greater than in mature and 45% and 46% greater than in dense habitat, for roe and muntjac respectively. Although differences in densities among model designs were not large, ignoring block or habitat effects gave higher estimates, while models that accounted for habitat-specific detectability gave lower (-8%) and more precise (38% reduction in CV) estimates (n = 3, muntjac: 5.3-7.5% CV; roe deer: 8.8-12.6% CV). The similarity of density estimates between ungrouped and grouped data and analysis of behaviour of detected deer support the conclusion that distance estimates were not biased by avoidance. We conclude that distance sampling using thermal imaging is a robust and powerful method for estimating deer density. In heterogeneous forest density estimates will be improved by accounting for varying detectability among growth stages or habitats.

    Item Type: Article
    Uncontrolled Keywords: thermal imaging,distance sampling,abundance estimation,capreolus capreolus,evidence-based management,muntiacus reevesi,ecology,forestry,nature and landscape conservation,ecology, evolution, behavior and systematics ,/dk/atira/pure/subjectarea/asjc/2300/2303
    Faculty \ School: Faculty of Science > School of Environmental Sciences
    Depositing User: Pure Connector
    Date Deposited: 24 Jun 2016 00:06
    Last Modified: 10 Apr 2019 00:52
    URI: https://ueaeprints.uea.ac.uk/id/eprint/59495
    DOI: 10.1016/j.baae.2015.06.005

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