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Cohort Affects Growth of Males but Not Females in Alpine Ibex (Capra ibex ibex)

C. Toïgo, J.-M. Gaillard, J. Michallet
DOI: http://dx.doi.org/10.2307/1383272 1021-1027 First published online: 27 August 1999

Abstract

We studied long-term cohort effects on chest girth and horn length in a recently established population of alpine ibex (Capra ibex ibex). Environmental conditions of the year of birth affected chest girth and first-annual increment of horns of males but did not affect chest girth and horns of females. Females compensated for a slow horn growth during their 1st year of life, whereas males did not. Level of polygyny of the species and environmental conditions experienced by the population could account for the occurrence of long-term cohort effects in male growth and its absence in female growth. Abundance of food resources throughout the study period allowed females to show compensatory growth. However, evolutionary constraints on growth that may exist in males of polygynous species may have prevented males from showing compensatory growth.

Key words
  • Capra ibex ibex
  • horn length
  • chest girth
  • cohort
  • sexual selection