Differential fitness effects of moonlight on plumage colour morphs in barn owls

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The Moon cycle exposes nocturnal life to variation in environmental light. However, whether moonlight shapes the fitness of nocturnal species with distinct colour variants remains unknown. Combining data from long-term monitoring, high-resolution global positioning system tracking and experiments using prey, we show that barn owls (Tyto alba) with distinct plumage colourations are differently affected by moonlight. The reddest owls are less successful at hunting and providing food to their offspring during moonlit nights, which associates with lower body mass and lower survival of the youngest nestlings and with female mates starting to lay eggs at low moonlight levels. Although moonlight should make white owls more conspicuous to prey, it either positively affects or does not affect the hunting and fitness of the whitest owls. We experimentally show that, under full-moon conditions, white plumage triggers longer freezing times in prey, which should facilitate prey catchability. We propose that the barn owl’s white plumage, a rare trait among nocturnal predators, exploits the known aversion of rodents to bright light, explaining why, counterintuitively, moonlight has a lesser impact on the whitest owls. Our study provides evidence for the long-suspected influence of the Moon on the evolution of colouration in nocturnal species, highlighting the importance of colour in nocturnal ecosystems.


  • Luis M. San-Jose
  • Robin Séchaud
  • Kim Schalcher
  • Clarisse Judes
  • Anastasia Questiaux
  • Aymeric Oliveira-Xavier
  • Charlène Gémard
  • Bettina Almasi
  • Paul Béziers
  • Almut Kelber
  • Arjun Amar
  • Alexandre Roulin
Enheter & grupper
Externa organisationer
  • The Swiss Ornithological Institute
  • University of Cape Town
  • University of Lausanne

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Evolutionsbiologi
Sidor (från-till)1331-1340
Antal sidor10
TidskriftNature Ecology and Evolution
Utgåva nummer9
StatusPublished - 2019
Peer review utfördJa