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Similar estimates of population genetic composition and sex ratio derived from carcasses and faeces of Eurasian otter Lutra lutra

Authors

  • John F. Dallas,

    Corresponding author
    1. NERC Molecular Genetics in Ecology Initiative, Zoology Building, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK;
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  • Karen E. Coxon,

    1. School of Biological Sciences, University of Exeter, Hatherly Laboratories, Prince of Wales Road, Exeter EX4 4PS, UK;
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  • Tim Sykes,

    1. The Environment Agency, Hampshire and Isle of Wight Area Office, Wessex Business Park, Wessex Way, Colden Common, Winchester, Hampshire SO21 1WP, UK;
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  • Paul R. F. Chanin,

    1. School of Biological Sciences, University of Exeter, Hatherly Laboratories, Prince of Wales Road, Exeter EX4 4PS, UK;
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  • Freda Marshall,

    1. NERC Molecular Genetics in Ecology Initiative, Zoology Building, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK;
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  • David N. Carss,

    1. Centre for Ecology and Hydrology Banchory, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, Scotland, UK
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  • Philip J. Bacon,

    1. Centre for Ecology and Hydrology Banchory, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, Scotland, UK
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  • Stuart B. Piertney,

    1. NERC Molecular Genetics in Ecology Initiative, Zoology Building, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK;
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  • Paul A. Racey

    1. NERC Molecular Genetics in Ecology Initiative, Zoology Building, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK;
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J. F. Dallas. E-mail: j.dallas@abdn.ac.uk

Abstract

Collecting faeces is viewed as a potentially efficient way to sample elusive animals. Nonetheless, any biases in estimates of population composition associated with such sampling remain uncharacterized. The goal of this study was to compare estimates of genetic composition and sex ratio derived from Eurasian otter Lutra lutra spraints (faeces) with estimates derived from carcasses. Twenty per cent of 426 wild-collected spraints from SW England yielded composite genotypes for 7–9 microsatellites and the SRY gene. The expected number of incorrect spraint genotypes was negligible, given the proportions of allele dropout and false allele detection estimated using paired blood and spraint samples of three captive otters. Fifty-two different spraint genotypes were detected and compared with genotypes of 70 otter carcasses from the same area. Carcass and spraint genotypes did not differ significantly in mean number of alleles, mean unbiased heterozygosity or sex ratio, although statistical power to detect all but large differences in sex ratio was low. The genetic compositions of carcass and spraint genotypes were very similar according to confidence intervals of θ and two methods for assigning composite genotypes to groups. A distinct group of approximately 11 carcass and spraint genotypes was detected using the latter methods. The results suggest that spraints can yield unbiased estimates of population genetic composition and sex ratio.

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