A multidisciplinary team of scientists has investigated the night camouflage of white owls and has concluded that they become “invisible” in the moonlight, managing to camouflage themselves both when acting as predators and when they feel like prey.
This striking white color could be an adaptation that makes them harder to see for their prey when they fly against the night sky.
The researchers, led by scientists from the Doñana Biological Station (EBD-CSIC), published their findings in the journal PNAS. Camouflage is considered a daytime phenomenon, but the researchers wondered if an animal can camouflage itself at night.
The barn owl (Tyto alba), with its white ventral plumage, is different from other nocturnal raptors and presents plumages with complex designs that conceal them in their environment.
Juan José Negro, a specialist in behavioral ecology and researcher at the Doñana Biological Station, explained that the white plumage could represent a type of nocturnal camouflage.
The owl’s concealment would be achieved when the contrast between the predator and the sky is below the visual detection threshold of its prey, typically rodents seeking food on the ground.
Effect of moonlight on white owls
Invisibility to the mouse is proposed to not occur on completely cloudy or moonless nights, but on clear nights, the isotropy of the glow of the sky is altered if the moon is present.
This allows for a compensation between the light from the celestial vault behind the owl and the light reflected by it towards the ground where the prey is, making the owl almost undetectable to the mouse.
These results are consistent with previous observations indicating that, on full moon nights, whiter owls catch more prey than darker ones. This suggests that the white color can be an adaptive advantage in certain nocturnal light conditions.
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