This is because seed-dispersing bats avoid light-polluted areas, scientists explain

Mar 11, 2014 21:36 GMT  ·  By

According to a new paper in the Journal of Applied Ecology, light pollution can impair forest regeneration in tropical habitats.

This is not because growing vegetation gets stage fright when there is too much light available and refuses to show its face in public, but because seed-dispersing bats prefer to chiefly feed in dark areas.

This means that they seldom visit regions affected by light pollution. Consequently, they are not all that efficient at dispersing seeds in such areas, and forest regeneration is negatively affected.

Specialists with the German Leibniz Institute for Zoo and Wildlife Research Berlin explain that insect-eating bats have for some time now been known to prefer dark regions and avoid light-polluted areas.

They further detail that, as shown by a series of experiments that they carried out, fruit-eating bats display the same behavior, meaning that they do not forage in lit areas all that often. Science Daily reports that, in order to investigate how light pollution affects the behavior of seed-dispersing bats, researchers carried out several experiments on Sowell's short-tailed bats.

More precisely, they divided a light cage into two compartments, one naturally dark and one illuminated by a regular street lamp, and placed pepper plants, nightshade, and figs in each of them.

They then waited to see which compartment the bats preferred, and found that the creatures chose to visit the dark compartment twice as often as they did the one lit by the street lamp.

Later, the scientists illuminated pepper plants growing in the wild and found that the bats that visited them only fed on roughly 78% of the ripe fruit growing on them.

By comparison, pepper plants in dark areas had 100% of their ripe fruit harvested by the bats that paid them a visit, the researchers explain in their paper in the Journal of Applied Ecology.

This means that, in regions affected by light-pollution, plants are likely to have a more difficult time colonizing deforested areas due to the fact that seed-dispersing bats tend to keep away from them.

“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,” explains study first author Daniel Lewanzik.

Furthermore, “Under naturally dark conditions, bats produce a copious 'seed rain' when defecating seeds while flying. By reducing foraging of fruit-eating bats in lit areas, light pollution is likely to reduce seed rain, he commented.”

Daniel Lewanzik and his colleagues say that, due to economic and population growth, light pollution is likely to soon become an issue in many tropical countries. Given their findings, the specialists recommend that measures to keep it under control be implemented.

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