Sexual and geographic dimorphism in northern rockhopper penguins breeding in the South Atlantic Ocean
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Issue date
2019-08-22Submitted date
2020-01-06Subject Terms
Northern rockhopper penguinEudyptes moseleyi
Sexual dimorphism
Discriminant function analysis
Morphological sexing
Morphometrics
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Show full item recordAbstract
The Endangered northern rockhopper penguin Eudyptes moseleyi, like all penguins, is monomorphic, making sex determination of individuals in the field challenging. We examined the degree of sexual size dimorphism of adult birds across the species’ breeding range in the Atlantic Ocean and developed discriminant functions (DF) to predict individuals’ sex using morphometric measurements. We found significant site-specific differences in both bill length and bill depth, with males being the larger sex on each island. Across all islands, bill length contributed 78% to dissimilarity between sexes. Penguins on Gough Island had significantly longer bills, whilst those from Tristan da Cunha had the deepest. Island-specific DFs correctly classified 82-94% of individuals, and all functions performed significantly better than chance. The model for Nightingale Island correctly classified the greatest proportion of individuals (94-95%), while that for Tristan da Cunha performed the poorest (80-82%). A discriminant function derived from all sites accurately sexed 86-88% of northern rockhopper penguins achieving similar accuracy to island-specific functions. While molecular techniques conclusively determine an individual’s sex, morphometric measurements can provide a reliable estimate with close to 90% accuracy using a method that is less invasive and requires little technical expertise. Sexing is an important tool for meaningful interpretation of ecological data. Consideration of sex-specific differences in future studies will aid investigation of a potential sex-dependent vulnerability in this Endangered species.Citation
Steinfurth A, Booth JM, White J, Bond AL, McQuaid CD (2019) Sexual and geographic dimorphism in northern rockhopper penguins breeding in the South Atlantic Ocean. Endang Species Res 39:293-302. https://doi.org/10.3354/esr00970Publisher
Inter-Research Science CenterJournal
Endangered Species ResearchDOI
10.3354/esr00970Type
Journal ArticleItem Description
© The authors 2019. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are unrestricted. Authors and original publication must be credited. The attached file is the published pdf.ISSN
1863-5407EISSN
1613-4796ae974a485f413a2113503eed53cd6c53
10.3354/esr00970
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