60-Second Earth

Lighting May Cut Seed-Rich Bat Guano Production

Bats ate less fruit in lit areas than in dark ones, which may lessen their seed-dispersal activities needed to bring back slashed rainforests. Cynthia Graber reports.


Worldwide, rainforests are slashed for agriculture and logging. When a plot of land is used up, it’s often abandoned. Which should allow the rainforest to regenerate. But along with roads and buildings comes lighting. And the artificial light may hamper forest regrowth. Because fruit-eating bats that ordinarily leave behind a rich trail of seeds may decrease their feeding in lit areas.

That’s according to a study in the Journal of Applied Ecology. [Daniel Lewanzik and Christian C. Voigt, Artificial light puts ecosystem services of frugivorous bats at risk]

Researchers looked at captive bats, able to feed from a dark compartment or one dimly lit. And the bats took twice as much food from the dark space as from the lit one.

The researchers also monitored wild bats that fed on fourteen plants ripe with fruit. Each plant could be kept in darkness or illuminated by a street light. Bats harvested fruit from the dark plants quickly and thoroughly. But their take was delayed and decreased on the lit plants.

The researchers conclude that light could interfere with the activities of seed-dispersing bats and thus stall rainforest regeneration. They recommend that artificial outdoor light in deforested tropical areas be restricted. So that bats will eat and let the seeds fall where they may.

—Cynthia Graber

[The above text is a transcript of this podcast.]

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