Importance of melanin-based colouration and environment in shaping intracellular glutathione levels in nestling and adult tawny owls Strix aluco

Guillaume Emaresi, Pierre Bize, Alexandre Roulin* (Corresponding Author)

*Corresponding author for this work

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Resources allocated in reproduction are traded off against those invested in self-maintenance such as antioxidant response. Glutathione (GSH) is an intracellular antioxidant defence that scavenges reactive oxygen species, the deleterious byproducts of oxygen consumption. Given the role of intracellular GSH in pheomelanogenesis, a trade-off in GSH allocation between oxidative stress and melanin production may take place. To investigate how intracellular GSH is regulated in differently coloured individuals at the time of reproduction (in adults) and of intense melanogenesis (in nestlings), we measured the total pool of GSH produced (tGSH), consumed (oxGSH) and available (redGSH) in adult tawny owls and their offspring which were cross-fostered between randomly chosen nests. Our goal was to describe potential correlations between resistance in oxidative stress and colour morphs in natural conditions. Nestling GSH levels
were correlated with GSH levels in their genetic and foster parents suggesting that producing GSH is genetically and environmentally determined (although the effect of the foster nest seemed stronger). This species shows continuous variation in pheomelanin reddish colouration, which is associated with life-history strategies. Based on the hypothesis of GSH dependence of pheomelanism, we expected a greater amount of oxGSH in dark compared to light pheomelanic nestlings, which was not the case. In contrast, light melanic breeding adults had higher levels of tGSH and redGSH than dark breeders probably because of a higher investment in antioxidant capacity. The link between pheomelanism and GSH may therefore be due to the fact that differently colored individuals have different life-history strategies rather than because the production of pheomelanin pigments requires GSH.
Original languageEnglish
Article numbere02908
Number of pages14
JournalJournal of Avian Biology
Issue number2
Early online date23 Nov 2021
Publication statusPublished - Feb 2022

Bibliographical note

Acknowledgements – We are grateful to Isabelle Henry, Arnaud Da Silva, Mélissa Noll, Sophie Cotting, Adrian Moriette and Alexandre Chausson for assistance in the field and the Swiss National Science Foundation for financial support (PPOA-102913 and 3100AO_120517 to AR).
Funding – Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung.

Data Availability Statement

Data are available from the Dryad Digital Repository: <> (Emaresi et al. 2021).


  • colour polymorphism
  • glutathione
  • melanin
  • oxidative stress
  • pheomelanin


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