Reproductive costs of sons and daughters in Rocky Mountain bighorn sheep |
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Authors: | Berube Celine H; Festa-Bianchet Marco; Jorgenson John T |
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Institution: | aGroupe de recherche en ecologie, nutrition et energetique, Departement de biologie, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada,
bAlberta Fish and Wildlife, Box 1059, Canmore, Alberta TOL 0M0, Canada |
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Abstract: | Differential maternal investment theory predicts that in sexuallydimorphic and polygynous species mothers should invest morein sons than in daughters. We tested the hypothesis that bighornewes that raise sons incur greater reproductive costs than ewesthat raise daughters. Although ewe mass gain during lactationand subsequent winter body mass loss were independent of lambsex, lambs born the year following the weaning of a son hadlower survival than lambs born after a daughter. The effectsof lamb sex on subsequent reproductive success of ewes becamemore evident at high population density. Lamb sex did not affectmaternal survival. Population density, weather, and ewe agedid not alter the relationship between lamb sex and subsequentreproductive success of the ewe. The year after weaning a son,ewes were more likely to have a daughter than a son, while ewesthat had previously weaned a daughter had similar numbers ofsons and daughters. Our results show that for bighorn sheepewes, sons have a greater life-history cost than daughters,suggesting a differential maternal investment in the sexes. |
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Keywords: | costs of reproduction differential maternal investment Ovis canadensis reproductive success sex ratio |
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