Nav: Home

When does noise become a meaningful message?

February 06, 2019

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 sound 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 bats 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 species delayed their emergence from their roosts when they heard the sound of rain.

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 negative consequences," Geipel said. "But through this study we show that noise 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."
-end-
Reference: Geipel, I., Smeekes, M.J., Halfwerk, W., Page, R.A. 2019. Noise as an informational cue for decision making: the sound of rain delays bat emergence. Journal of Experimental Biology. 222, jeb192005. doi:10.1242/jeb.192005

Smithsonian Tropical Research Institute

Related Bats Articles:

How bats relocate in response to tree loss
Identifying how groups of animals select where to live is important for understanding social dynamics and for management and conservation.
Bats use private and social information as they hunt
As some of the most savvy and sophisticated predators out there, bats eavesdrop on their prey and even on other bats to collect a wide variety of information as they hunt.
There are way more species of horseshoe bats than scientists thought
Horseshoe bats are bizarre-looking animals with giant ears and elaborate flaps of skin on their noses that they use like satellite dishes.
What a group of bizarre-looking bats can tell us about the evolution of mammals
Bats with skulls and teeth adapted to a wide range of diets are helping scientists understand how major groups of mammals first evolved.
Fruit bats can transform echoes into images
A new Tel Aviv University study finds that fruit bats actually integrate vision and echolocation to flourish in the dead of night.
More Bats News and Bats Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...