Official websites use. Share sensitive information only on official, secure websites. Correspondence: luismsanjose gmail. 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 long-term monitoring, high-resolution GPS tracking, and experiments on prey, we show that barn owls Tyto alba with distinct plumage colourations are differently affected by moonlight. The reddest owls are less successful hunting and providing food to their offspring during moonlit nights, which associates with lower body mass and 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, hunting and fitness of the whitest owls are positively or un-affected by moonlight. We experimentally show that, under full-moon conditions, white plumages trigger longer freezing times in the prey, which should facilitate prey catchability. 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.
Colouration largely determines how animals interact with their biotic and abiotic environment 1. The latter component may shape the evolution of colouration, with heterogeneous light conditions favouring distinct colourations as shown, for instance, in African cichlid fish living at different depths 4 , 5 or in birds exploiting the canopy and the understorey of tropical forests, inhabiting less vs.
However, most of the studies linking variation in environmental light and colouration come from diurnal species and the consequences that variation in nocturnal light has for the evolution of animal colouration are barely known 9. The Moon has shadowed the evolution of life, which adapts its endogenous rhythms to the lunar cycle 10 β By producing contrasting changes in light conditions 23 , the Moon might also drive the evolution of colouration in nocturnal animals, but this hypothesis has received little attention despite being proposed more than a hundred years ago This could explain why colouration of nocturnal species has often been considered as an adaptation for diurnal camouflage rather than for a nocturnal life In line with the accumulation of studies highlighting the importance of colour vision in nocturnal species 23 , 28 , 29 , a few recent studies have indirectly addressed how nocturnal light variation relates to animal colouration.
