Behavioral Ecology and Sociobiology

, Volume 31, Issue 4, pp 243–251

Sex-biased maternal expenditure in Rocky Mountain bighorn sheep

  • John T. Hogg
  • Christine C. Hass
  • Donald A. Jenni
Article

DOI: 10.1007/BF00171679

Cite this article as:
Hogg, J.T., Hass, C.C. & Jenni, D.A. Behav Ecol Sociobiol (1992) 31: 243. doi:10.1007/BF00171679

Summary

We examined maternal energy expenditure in Rocky Mountain bighorn sheep to test the hypothesis (Trivers and Willard 1973) that individual sons in polygynous mammals should obtain a larger maternal subsidy. In accord with theory, males weighed more at birth (an index of relative prenatal expenditure), tended to suckle more between 40 and 100 days of age (an index of relative postnatal expenditure) and imposed greater delays on their mothers' return to estrus in the subsequent breeding season (an index of relative total preweaning expenditure). Mothers rather than offspring appeared to have primary control over postnatal expenditure. The effect of maternal reproductive effort on return to estrus was cumulative over a period of 3–5 years so that ewes making relatively large expenditures gave birth progressively later. Ewe and lamb mortality was associated with late conception in the previous rut. Thus, differential reproductive effort by ewes in this population appeared to entail a fitness cost involving reductions in both offspring and maternal survivorship.

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • John T. Hogg
    • 1
  • Christine C. Hass
    • 1
  • Donald A. Jenni
    • 1
  1. 1.Division of Biological SciencesUniversity of MontanaMissoulaUSA
  2. 2.Craighead Wildlife-Wildlands InstituteMissoulaUSA
  3. 3.Department of BiologyUniversity of North DakotaGrand ForksUSA

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