Testing the interactive effects of testosterone and parasites on carotenoid-based ornamentation in a wild bird

J. Martinez-Padilla*, F. Mougeot, L. M. I. Webster, L. Perez-Rodriguez, S. B. Piertney

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)


Testosterone underlies the expression of most secondary sexual traits, playing a key role in sexual selection. However, high levels might be associated with physiological costs, such as immunosuppression. Immunostimulant carotenoids underpin the expression of many red-yellow ornaments, but are regulated by testosterone and constrained by parasites. We manipulated testosterone and nematode burdens in red grouse (Lagopus lagopus scoticus) in two populations to tease apart their effects on carotenoid levels, ornament size and colouration in three time-step periods. We found no evidence for interactive effects of testosterone and parasites on ornament size and colouration. We showed that ornament colouration was testosterone-driven. However, parasites decreased comb size with a time delay and testosterone increased carotenoid levels in one of the populations. This suggests that environmental context plays a key role in determining how individuals resolve the trade-off between allocating carotenoids for ornamental coloration or for self-maintenance needs. Our study advocates that adequately testing the mechanisms behind the production or maintenance of secondary sexual characters has to take into account the dynamics of sexual trait expression and their environmental context.

Original languageEnglish
Pages (from-to)902-913
Number of pages12
JournalJournal of Evolutionary Biology
Issue number5
Early online date7 Apr 2010
Publication statusPublished - May 2010


  • carotenoids
  • honest signalling
  • red grouse Lagopus lagopus scoticus
  • sexual selection
  • Trichostrongylus tenuis
  • Lagopus-lagopus-scoticus
  • male red grouse
  • immunocompetence handicap hypothesis
  • mediated trade-offs
  • Trichostrongylus-tenuis
  • sexual attractiveness
  • plumage coloration
  • colorful songbird
  • territorial behavior
  • immune activation


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