When does noise become a message?

February 6, 2019, Smithsonian Tropical Research Institute
Inga Geipel, postdoctoral fellow at the Smithsonian Tropical Research Institute in Panama, asked how the sound of rain would affect the behavior of two insect-eating bats. Credit: Claudia Rahlmeier

Background noise is generally regarded as a nuisance that can mask important sounds. But noise can be beneficial too. It can convey information about important environmental conditions and allow animals to make informed decisions. When bat researchers recorded and played back rain sounds for two different species of bats, both species chose to delay emergence from their roosts.

"Bats are acoustic specialists," said Inga Geipel, a Tupper Postdoctoral Fellow at the Smithsonian Tropical Research Institute in Panama. "They are active at night and depend on to navigate their environment and to find food. When they hear the sound of rain at sunset, they decide to stay inside their roosts for a while longer."

Bats have good reasons not to want to go out in the rain, as wet spend more energy when flying. Further, rain might also have a strong impact on the bats ability to navigate and find food through sound. Rain noise could mask prey sounds or jam the echolocation system of the hunting bats.

Geipel and colleagues investigated the effect of rain noise on bat decision making. They studied two different species of bats: the common big-eared bat (Micronycteris microtis), which catches insects from leaves and other surfaces in forest understory, and the Pallas's mastiff bat (Molossus molossus) that hunts insects on the wing as they fly through open spaces.

"We wondered whether bats are staying longer in the safety of their roosts during rain storms and whether noise would inform them about the rainfall outside," Geipel said.

To test their ideas, Geipel and her team put a speaker near entrances of bat roosts and broadcast recordings of heavy downpours. Simultaneously, they video-recorded the responses of the bats. For comparison, they also played recordings of normal forest sounds. Both delayed their emergence from their roosts when they heard the sound of .

The scientists also observed that the big-eared bats rapidly flew in and out of their roosts on short 'exploration flights,' likely meant to gather direct information about environmental conditions.

"Noise is often thought to be a nuisance with ," Geipel said. "But through this study we show that can actually be used as a salient informational cue. It can provide individuals with important information about their environment and when it's safe to hunt."

Explore further: Predators learn to identify prey from other species

More information: Inga Geipel et al, Noise as an informational cue for decision-making: the sound of rain delays bat emergence, The Journal of Experimental Biology (2019). DOI: 10.1242/jeb.192005

Related Stories

Predators learn to identify prey from other species

March 21, 2018

Wolves purportedly raised Romulus and Remus, who went on to rule Rome. Is there good scientific evidence for learning across species? Researchers at the Smithsonian Tropical Research Institute (STRI) in Panama wanted to know ...

Why does rain keep bats grounded?

May 5, 2011

(PhysOrg.com) -- In a new study published in Biology Letters, researcher Christian Voigt from the Leibniz Institute for Zoo and Wildlife Research in Germany details their findings on Sowell’s short-tailed bats and the ...

Bats use second sense to hunt prey in noisy environments

September 15, 2016

Like many predators, the fringe-lipped bat primarily uses its hearing to find its prey, but with human-generated noise on the rise, scientists are examining how bats and other animals might adapt to find their next meal. ...

How bats fly to find their prey

June 18, 2015

New research, complete with night-vision video recordings, helps elucidate how bats actually fly to find their prey.

Researchers observe novel bat behavior in Panama

October 25, 2018

Baby birds learn to fly. Baby mammals switch from milk to solid food. Baby bats, as winged mammals, do both at the same time during their transition from infants to flying juveniles. According to a new report from researchers ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

NASA instruments image fireball over Bering Sea

March 22, 2019

On Dec. 18, 2018, a large "fireball—the term used for exceptionally bright meteors that are visible over a wide area—exploded about 16 miles (26 kilometers) above the Bering Sea. The explosion unleashed an estimated 173 ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.