Stadium lights alter bat behavior, study says

Researchers say stadium lighting may impact bat feeding patterns, creating a possible threat to local biodiversity.

Science Notebook

Friday night lights are good for the game, but they may be bad for biodiversity.

According to a study published Friday in the journal Animal Conservation, bright stadium lighting could affect the feeding habits of bats. Insects swarm these lights in large numbers, creating a competitive advantage for bat species who aren’t afraid of humans and human structures. This could impact local ecosystems and diminish biodiversity, researchers say.

For most humans, there simply isn’t enough daylight hours – we have been developing new ways to illuminate the night since we first harnessed fire. But researchers say our need for perpetual visibility can have serious consequences for neighboring species.

Light pollution has been linked to ecosystem damage on several fronts. Turtle hatchlings, for example, instinctively use the light of the moon to navigate towards the open ocean. But incessant and poorly designed artificial lighting can throw off their sense of direction, significantly disrupting their life cycles.

"Increasing light pollution is a major feature of global change that's attributable to humans, and it is a potential threat to biodiversity," co-author M. Corrie Schoeman said in a press release.

Dr. Schoeman, a professor of biology at the University of Kwazulu-Natal, conducted field experiments to determine how stadium lighting affected bat behaviors. He found that "urban exploiter" bats were drawn to hunt near bright lights, while "urban avoider" bats were not. Exploiter species are able to take advantage of human resources, such as artificial light. Avoider species, by comparison, tend to avoid humans and human structures.

But it’s hardly survival of the fittest. This man-made, ecological scale-tipping could result in the decline or loss of avoider species. And that, in turn, could threaten the balance of local ecosystems.

"Although stadiums are an integral part of the urban and social environment," Schoeman said, "light pollution from these structures could lead to biotic homogenization, which may ultimately threaten native biodiversity."

Luckily, light pollution is considered an "easy fix" compared to other forms of pollution. Smart lighting design – hooded streetlamps, motion-sensitive residential lights, and better controls to eliminate unnecessary brightness – can significantly reduce light pollution. As for stadium lights, earlier games could do a lot of good, both for bats and our ecosystems as a whole.