Do carotenoids buffer testosterone-induced immunosuppression? An experimental test in a colourful songbird

Kevin McGraw, Daniel R. Ardia

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


Testosterone (T) is hypothesized to be an important honesty reinforcer of animal sexual signals. Owing to its immunosuppressive effects, only those individuals that can immunologically withstand high T levels can develop the most exaggerated traits. To date, few studies have isolated phenotypic or genotypic buffers that provide 'high-quality' animals with such an advantage. Dietary carotenoid pigments may in fact confer such a benefit because when in high supply carotenoids boost immunocompetence and coloration in animals like birds and fishes. We examined the experimental effect of T elevation on carotenoid and immune status in male and female zebra finches (Taeniopygia guttata) and found that T was immunostimulatory in a generalized cell-mediated challenge. We also detected a significant interaction between T treatment and the change in plasma carotenoids that occurred during the immune challenge; the relationship between blood carotenoid change and immunity was positive in controls and negative in T-implanted birds. This suggests that, while correlationally birds with high carotenoid stores were inherently better at mounting strong immune responses, experimentally administered T induced birds to deplete carotenoids for maximizing their health. Our findings highlight a nutrient-specific mechanism by which animals escape high immune costs of T elevation and thus can still elevate ornamentation.

Original languageEnglish (US)
Pages (from-to)375-378
Number of pages4
JournalBiology letters
Issue number4
StatePublished - Aug 22 2007


  • Carotenoid coloration
  • Hormones
  • Immunity
  • Taeniopygia guttata
  • Zebra finch

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Agricultural and Biological Sciences(all)


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