Moonlight scares bats into hiding in the shadows, new research suggests.
Scientists in Mexico collated studies of bat behaviour from all over the world and analysed them for evidence of "lunar phobia" or "fear of the moon".
The study found that the activity of bats in moonlit habitats decreased on bright nights compared with bats that live and forage in darker places.
This may be explained by a higher risk of predation and lack of feeding opportunities in moonlight, it found.
The findings are published in the journal Mammalian Biology and represent what scientists have called "the first reliable evaluation of the lunar phobia phenomenon".
The study brought together a wide range of research concerning how these nocturnal animals behave and interact with the light of the moon.
"Evidence that the activity of bats decreased with increasing intensity of moonlight was contradictory, so that's why we decided to conduct this research," said the study's lead author, Mr Romeo Saldana-Vazquez, a biologist at the National Autonomous University of Mexico.
"The effect of moonlight on the activity of bats had not been revised despite the existence of information accumulated over 20 years in different parts of the world," he said.
Drawing on data about 26 species from 11 studies, scientists modelled the activity of bats at different latitudes and in different habitats against the phases of the moon.
The analysis concluded that lunar phobia is "common among bats" and showed that the reduction in activity in moonlight differed depending on habitat type.
"Habitats where light enters more easily causes more bat-activity decreases compared with bats that forage in the darkest places," said Mr Saldana-Vazquez.
Species that forage over water and beneath the forest canopy showed considerably more lunar phobia than those in sheltered habitats, according to the study.
Scientists suggest that this may be because out in the open, the moonlight means these bats can be more easily spotted by predators.
Another factor could be that the bats' prey becomes more scarce when there is more light.
The scientists also linked bats that lived closer to the equator to a stronger form of lunar phobia, though this may have been caused by differences between bat species and their ecosystems, rather than the brightness of the moon in tropical regions.
One exception was found to be bats that fly above the treetops. These species did not tend to decrease their activity on brighter nights.
Mr Saldana-Vazquez said it is possible that this is because these bats tend to fly fast and live in temperate climates where bats have fewer predators.
"We think that this study will help to re-open the debate about the existence of a widespread pattern," added Mr Saldana-Vazquez. He now hopes that the questions raised by the study will be investigated further.
"For example assess[ing] the density of predators and prey in studies of bat foraging activity... could provide more insights into the mechanism behind the reduction in activity of bats, and the possible mechanisms behind the evolution of [these] behaviour patterns," he said.
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Source: http://www.bbc.co.uk/nature/19719986
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