Problems with primate sex ratios

Craig Packer, D. A. Collins, Lynn E Eberly

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


Birth sex ratios of baboons in Gombe National Park, Tanzania, show an overall male bias of ca. 20%, but there is no obvious explanation for this trend. Individual females did not alter their sex ratios according to persistent levels of local resource competition. Sex ratios showed an unexpected relationship between age and rank: subordinate females had more sons when they were young; dominant females had more sons when they were old. The sex ratio of low-ranking females also varied with the severity of environmental conditions during pregnancy. Our findings suggest that mammalian sex ratios might be the product of more complex processes than is generally recognized or that sex-determining mechanisms impose sufficient constraints to prevent adaptive variation in all contexts.

Original languageEnglish (US)
Pages (from-to)1627-1635
Number of pages9
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Issue number1403
StatePublished - Nov 29 2000


  • Local resource competition
  • Primates
  • Sex ratio


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