Cooper, NBond, ALDavis, JLPortela Miguez, RTomsett, LHelgen, Kristofer2019-10-282019-10-282019-10-232019-10-25Cooper Natalie, Bond Alexander L., Davis Joshua L., Portela Miguez Roberto, Tomsett Louise and Helgen Kristofer M. Sex biases in bird and mammal natural history collections286Proc. R. Soc. B http://doi.org/10.1098/rspb.2019.202510.1098/rspb.2019.2025http://hdl.handle.net/10141/622584Natural 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.closedAccesshttps://creativecommons.org/licenses/by/4.0/birds; mammals; museum specimens; natural history collections; sex biasJournal Article1471-2954Proc Biol Sci286191320192025 - ?mammalsnatural history collectionsmuseum specimensbirdssex bias