Behavioral Ecology and Sociobiology

, Volume 53, Issue 1, pp 25–30

Sex-ratio variation in Soay sheep

  • Jan Lindström
  • Tim Coulson
  • Loeske Kruuk
  • Mads C. Forchhammer
  • Dave W. Coltman
  • Tim Clutton-Brock
Original Article

DOI: 10.1007/s00265-002-0545-4

Cite this article as:
Lindström, J., Coulson, T., Kruuk, L. et al. Behav Ecol Sociobiol (2002) 53: 25. doi:10.1007/s00265-002-0545-4

Abstract.

We studied the effects of ecological variables on the birth sex ratio of Soay sheep (Ovis aries) lambs on the island of Hirta, in the St Kilda archipelago, Scotland. Both individual- and population-level models were constructed. In the individual-based model, only population size was significantly associated with the sex of a lamb, with the probability of giving birth to a male lamb being positively associated with population size. However, this model explained a very small proportion of the variance in birth sex ratio. A multiple regression analysis of the annual population birth sex ratio also showed a slight increase in the proportion of males born in years following high autumn population density, but this result was not statistically significant. Population growth rate, Julian birthday, litter size, mother's age and weight, and the weather conditions during the gestation and neonatal period did not explain significant variation in the birth sex ratio.

Maternal effects Ovis aries Sexual size dimorphism St Kilda Trivers–Willard hypothesis 

Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Jan Lindström
    • 1
  • Tim Coulson
    • 1
  • Loeske Kruuk
    • 2
  • Mads C. Forchhammer
    • 1
  • Dave W. Coltman
    • 2
  • Tim Clutton-Brock
    • 1
  1. 1.Large Animal Research Group, Department of Zoology, Downing Street, University of Cambridge, Cambridge CB2 3EJ, UK
  2. 2.Institute of Cell, Animal and Population Biology, University of Edinburgh, King's Buildings, Edinburgh EH9 3JT, UK
  3. 3.Current address: Department of Population Ecology, Zoological Institute, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark
  4. 4.Current address: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
  5. 5.Current address: Institute of Biomedical and Life Sciences, Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, UK

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