Subscribe to our free daily newsletters
. Earth Science News .




Subscribe to our free daily newsletters



Bats Have Complex Skills To Deal With Clutter

This study concentrated on sonar strobe groups emitted by Big Brown Bats.
by Staff Writers
College Park MD (SPX) Mar 08, 2006
A little clutter on the way to the refrigerator might mean taking a few extra seconds to navigate your way to a late night snack. For a bat flying around in the dark searching for a meal of insects, the "clutter" of things like leaves and trees could mean missing out on a tasty morsel of dinner altogether.

A bat finds its way around with sound rather than sight. Using a sensory process called echolocation, the bat emits ultrasonic pulses that hit objects like leaves, trees and insects, and bounce back to the bat to tell it what's in the vicinity. When an echo returns from "clutter" at the same time a sound bounces back from an insect, the bat has a real challenge figuring out where the bug is.

In an article in the March 6 issue of PLoS Biology, University of Maryland psychology professor Cynthia Moss reports on her new research that shows bats have methods for echolocating food in "clutter" that may be more complex than scientists have thought.

"We have found that bats adjust the timing of their sounds when they encounter clutter, and they seem to 'strobe' the world with sound," says Moss.

Moss also found that, contrary to the long held belief that a bat's sonic pulse output is tied only to its respiration and wingbeat, bats, in fact, adjust their sonic pulse output to respond to information they receive from echolocation.

The research is the latest of several recent studies by the Moss lab that are adding detailed new information to scientists' understanding of how acoustic signals drive bat behavior.

In its hunt for prey, a bat flies around at high speeds, emitting pulses of varying pitches and speeds. As the bat gets closer to what could be an insect, it sends out an array of quick repetitive pulses, called sonar strobe groups. Finally, when it has locked onto the bug, right before scooping it up, the bat shoots a rapid fire series of sounds called the final buzz. This study concentrated on sonar strobe groups emitted by Big Brown Bats.

"This species of bat has been observed capturing insects near the ground and vegetation, which suggests they have a wider repertoire of sonar-guided behavior than previously recognized," says Moss. "We thought the sonar strobe groups might be well suited to helping the bat distinguish a small object from the more complex background you would find in the wild."

Using an array of high-speed infrared cameras and strategically placed microphones in the "Batlab," Moss's team was able to match slowed video and audio recordings of the bat's echolocation activity and corresponding movement as it pursued an insect tethered to a string.

When nothing was blocking the insect, the bats made quick work of locating and capturing their prey. They attempted and succeeded at capture each time, with a small amount of strobing and a strong final buzz. The effort took only two seconds.

Then the researchers cluttered the hunting area by adding a plant. Dinner suddenly became harder to come by. The bats' incidence of strobing was higher and the hunt times longer, the closer the bug was placed to the plant. And the bat flew alongside the plant instead of going right for the insect.

When the plant was closest to the bug 10 centimeters the bats went for the prey only half of the time and usually failed. It took the bats an average of almost a minute and half to abort or fail. When the plant was moved farther away from the bug, the success rate went up and the hunt time started back down. At a 20-centimeter distance, the attempt and success rate shot back up, to 80 percent, with a hunt time of only a few seconds.

"In each case we found that the bats spent more time strobing when the insect was positioned near a plant, a strong indication that they used sonar strobe groups to try to distinguish the insect from the background clutter," Moss says. "They also varied the intervals between pulses in the strobe group, depending on the distance between the prey and clutter."

Moss's team also discovered that the bat's sonar pulsing is not based strictly to its wingbeat cycle, as has been thought. The wingbeat cycle is tied to the bat's breathing it inhales on the downstroke and exhales on the upstroke.

"Breaks in the sonar strobe groups would be expected to occur during a particular phase of the downstroke if wingbeat and respiration were strictly driving the production of sound groups," says Moss. "But we found that the sound groups occur across all phases of the wingbeat cycle, and definitely through the entire final buzz. This suggests that the bat's vocal control can override the wingbeat-respiration cycle.

"Most importantly," says Moss, "the results of this study clearly show that bats control the timing of their calls to directly influence the patterns of echoes used for perception."

Other researchers were Kari Bohn and Hannah Gilkenson of the University of Maryland, and Annemarie Surlykke, University of Southern Denmark. The research was funded by grants from the National Science Foundation, National Institutes of Health, the Danish National Research Foundation and the Danish Natural Science Research Council.

Related Links
University of Maryland, College Park
PLoS Biology

Threat To Last Stronghold Of Endangered Turtle
Exeter, UK (SPX) Mar 08, 2006
A major conservation effort, led by Dr Brendan Godley of the University of Exeter, has just got underway to help protect endangered leatherback turtles which nest in Gabon, West Africa. The region is thought to be the animals' last global stronghold, as pacific populations dwindle precariously.







  • Agami Systems Eases Access Critical Disaster-Relief Imagery in Near Real-Time
  • Study Finds Californians Unmotivated To Prepare For Next Disaster
  • The Future Of Foreign Assistance
  • High Post-Hurricane Rents Push People Out Of New Orleans

  • WFP Warns Of "Large Scale" Deaths In Kenyan Drought Crisis
  • IODP Scientists Acquire 'Treasure Trove' Of Climate Records Off Tahiti Coast
  • Massive Ancient Flood Linked To Climate Change
  • Fossil Wood Gives Vital Clues To Ancient Climates

  • International Symposium On Radar Altimetry To Meet In Venice
  • Satellites Ensure Safe Passage Through Treacherous Waters In Ocean Race
  • ESA Satellite Program Monitors Dangerous Ocean Eddies
  • Envisat Marks Fours Year In ESA Mission To Planet Earth

  • World's Poor Can Have Energy Without More Global Warming
  • New Techs, Ideas Can Help In Bid Counter Global Warming
  • Research Reveals Hidden Magnetism In Superconductivity
  • Researchers Find Ways Heat-Loving Microbes Release Energy

  • Crippling Indian Ocean Epidemic Detected in France
  • People of African Descent More Vulnerable to TB
  • Americans Downplay Widespread Outbreak Of Avian Flu In Next Year
  • Learning To Love Bacteria

  • Threat To Last Stronghold Of Endangered Turtle
  • Bats Have Complex Skills To Deal With "Clutter"
  • Plants Eavesdrop For Their Own Protection
  • Smallest Triceratops Skull Described

  • Particlates Increase Hospital Admissions For Cardiovascular Disease
  • Manila's Garbage Dump Offers Lifeline For Poor
  • Pesticides In The Nation's Streams And Ground Water
  • Czechs, Slovaks Agree To Cooperate Against German Waste Dumping

  • Humans Are Still Evolving
  • Magdalenian Girl Has Oldest Recorded Case Of Impacted Wisdom Teeth
  • World's Oldest Ship Timbers Found In Egyptian Desert
  • Archaeologists To Establish True Value Of Roman Silver Coins

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement