As human development continues to push into tropical habitats and roadside and building lamps are erected along the way, bats are being scared from fulfilling their vital roles in ecosystems, a new study out of Germany asserts.

New research by scientists from the Leibniz Institute for Zoo and Wildlife Research Berlin, or IZW, and published in the British Ecological Society's Journal of Applied Ecology, is the first to demonstrate bats that typically help regenerate their habitats by dropping plant seeds as they go avoid feeding in areas illuminated at night by man-made lights.

Working with the short-tailed Carollia sowelli bats, which are commonly found from Mexico south into Panama, IZW researcher Daniel Lewanzik, the primary author of the study, allowed the creatures to choose whether to fly into a cage filled with a variety of favorite fruits and left naturally dark or another cage also filled with the same types of food, but lighted with the globe's most widely-used sodium street lamp.

It turned out the bats flew into the dark compartment, and also harvested the fruits contained inside, nearly twice as often as they did in the lit area.

In a second test, Lewanzik used a street lamp to illuminate pepper plants growing in the wild and compared the percentage of ripe fruit bats harvested from them to the percentage taken from plants in a dark location.

And, again, while bats harvested 100 per cent of the fruit from the plants left in the dark, only 78 percent of the fruit from the lighted plants was consumed.

The results added to a previous study that found insect-eating bats avoid foraging in lighted areas.

"In tropical habitats bat-mediated seed dispersal is necessary for the rapid succession of deforested land because few other animals than bats disperse seeds into open habitats," explained Lewanzik in a news release.

Under naturally dark conditions, bats defecate so many fruit seeds while flying, it creates a virtual "seed rain," said Lewanzik, so, when the foraging of fruit-eating bats is deterred by nigh-time lighting, it significantly impacts the amount of seed distribution.

"The impact of light pollution," Lewanzik suggested, "could be reduced by changes in lighting design and by setting up dark refuges connected by dark corridors for light-sensitive species like bats."