Sex biases in bird and mammal natural history collections

Natalie Cooper, Alexander L Bond, Joshua L Davis, Roberto Portela Miguez, Louise Tomsett, Kristofer M Helgen

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    36 Citations (Scopus)
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    Natural history specimens are widely used across ecology, evolutionary biology and conservation. Although biological sex may influence all of these areas, it is often overlooked in large-scale studies using museum specimens. If collections are biased towards one sex, studies may not be representative of the species. Here, we investigate sex ratios in over two million bird and mammal specimen records from five large international museums. We found a slight bias towards males in birds (40% females) and mammals (48% females), but this varied among orders. The proportion of female specimens has not significantly changed in 130 years, but has decreased in species with showy male traits like colourful plumage and horns. Body size had little effect. Male bias was strongest in name-bearing types; only 27% of bird and 39% of mammal types were female. These results imply that previous studies may be impacted by undetected male bias, and vigilance is required when using specimen data, collecting new specimens and designating types.

    Original languageEnglish
    Pages (from-to)20192025
    JournalProceedings of the Royal Society of London Series B-Biological Sciences
    Issue number1913
    Early online date23 Oct 2019
    Publication statusE-pub ahead of print - 23 Oct 2019


    • natural history collections
    • birds
    • sex bias
    • mammals
    • museum specimens


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