Sept. 21 (UPI) -- Researchers in Germany found fish exposed to artificial light during the night were bolder during the day.
In the lab, light pollution caused the test fish, guppies, to be more active at night. The artificial light also cause fish to emerge from their hiding places more quickly during the daytime.
The fish didn't become slower or lazier as a result of the increase in nighttime activity. Researchers found the guppies' swimming speed and social behavior was unaltered by light pollution.
A number of studies have documented the impacts of light pollution on animals and their ecosystems. The allure of a big city's bright lights can alter a bird's migration pattern. Light pollution can also interfere with coral's ability to spawn.
For the experiment, scientists exposed three groups of guppies to the same amount of light during the day and three different amounts of light at night. One group enjoyed complete darkness at night. The other two groups were exposed to different amounts of artificial light -- dim and bright.
Fish exposed to the brightest light were the quickest to leave their hiding spots during the day. The same fish spent more time swimming in the most exposed regions of the aquarium.
In the wild, bolder behavior could spell trouble for small fish.
"The consequences of this increased risk taking behaviour are difficult to predict, but it is possible that they could be more at risk of predation by birds or other fish," David Bierbach, researcher at the Leibniz Institute of Freshwater Ecology and Inland Fisheries, said in a news release.
Researchers detailed their work this week in the journal Scientific Reports.
"We suspect that the nocturnal light causes a stress response in the fish, and fish generally increase their risk taking when experiencing stress," said lead researcher Ralf Kurvers.