Horn growth but not asymmetry heralds the onset of senescence in male Alpine ibex (Capra ibex)

Authors

  • Achaz von Hardenberg,

    Corresponding author
    1. Département de Biologie, Université de Sherbrooke, J1K 2R1 Sherbrooke, Canada
    2. Alpine Wildlife Research Centre, Gran Paradiso National Park, via della Rocca 47, 10123 Torino, Italy
      All correspondence to: A. von Hardenberg. E-mail: achaz.von.hardenberg@usherbrooke.ca
    Search for more papers by this author
  • Bruno Bassano,

    1. Alpine Wildlife Research Centre, Gran Paradiso National Park, via della Rocca 47, 10123 Torino, Italy
    Search for more papers by this author
  • Maria del Pilar Zumel Arranz,

    1. Department of Animal Biology, University of Pavia, P.za Botta 9, 27100 Pavia, Italy
    Search for more papers by this author
  • Giuseppe Bogliani

    1. Department of Animal Biology, University of Pavia, P.za Botta 9, 27100 Pavia, Italy
    Search for more papers by this author

All correspondence to: A. von Hardenberg. E-mail: achaz.von.hardenberg@usherbrooke.ca

Abstract

Senescence can be defined as accelerating phenotypic deterioration with old age. For traits that grow throughout life, such as the horns of some ungulates, senescence may be expressed as a decrease in annual growth rates, or an increase in asymmetry, in the years preceding death. Age-specific yearly horn-growth segments of 378 male Alpine ibex Capra ibex L. that died from natural causes were analysed in the Gran Paradiso National Park (Italian Alps). Horn annuli displayed fluctuating asymmetry. The hypothesis that asymmetry and size of the annuli of the horns could predict annual survival probability was tested. It was found that between 5 and 11 years of age, male ibex that grew shorter annuli than the average for the population had a greater probability of mortality over the following years than those with greater rates of horn growth. Horn asymmetry and mortality rates were not significantly correlated. Annulus size, reflecting the onset of senescence, seemed to be a better indicator of individual quality than annulus asymmetry.

Ancillary