Friday, October 03, 2008

Hunting in a Mechanized World

We've always imagined bats to use echolocation in a quiet neighborhood to locate their next meal with pinpoint accuracy, but how well can they find their prey in a noisy and unnatural environment? In a recent study by Björn Siemers from the Max Planck Institute for Ornithology in Germany, Siemers tests to see if bat's hunting abilities are impaired by man made noises.

Siemers and his colleagues let a group of young male greater mouse-eared bats to forage for worms in a soundproof room divided into two equal parts. The bats spent an equal amount of time foraging in both areas of the room, locating their meals with ease, but with the presence of white noise in one half of the room, the bats spent over 80% of their time foraging in the quieter environment. Siemers next introduced a recording of a highway to one of the divided rooms. The bats were significantly less bothered by the highway noise, spending almost 40% of their time in the "highway" environment, and were still able to find their prey with precision. Oddly enough, the bats had a much more difficult time locating their quarry in a naturally made sound of rattling reed beds, a noise they may naturally encounter daily.

Although not completely sure how the bats are affected by man made noises, Siemers hopes his work will help build a more friendly environment to help protect these endangered species.

The full article can be found here.

Posted by Dan Hong (3)


Although not mentioned in the article, the greater mouse-eared bats are a European species. Their habitat generally lies near human settlements. They are currently in the status of endangered, and considered to be extinct within the United Kingdom.

White noise is simply a power density within a fixed bandwidth of a frequency. The greater mouse-eared bat uses echolocation with a frequency ranging from 22-86kHz. If a white noise were to be played within the range of these bat's echolocation frequency, it would be a disturbance, and their performance in locating prey could possibly be hindered. Man made noises, and possibly that of highway noises, would have a lower frequency than the frequency used for echolocation, which is a possible reason why these bats were not affected by the highway recordings.


At 2:44 PM, Anonymous Anonymous said...

I think bats are remarkable creatures. It is really cool how they foraged with the highway noise effectively, but not with the human made noises. I think we need to give these little guys some more credit. They really are an intelligent, and well adapted species.

Mia DiFabbio

At 5:42 PM, Blogger PWH said...

does the article mention the habitat of these bats? it is interesting to see that the highway noise didnt bother them but natural environment sounds distracted them.

Hessom Minaei

At 10:01 AM, Blogger PWH said...

I find the topic of this article interesting. I wonder how this scientist thinks that understanding the sounds that make hunting difficult for bats will help to better protect them? I'm sure that anything that can be learned from them would be of help but I think that there are more pressing problems facing bats right now. Problems such as the fungus that is wiping out bats at a phenomenal rate. I also wonder what is the difference between white noise and regular noise? There must be some sort of frequency difference and how does this exactly affect a bats echolocation abilities? Also where might bats experience white noise?

Posted by: Lindsay Goodyear

At 1:32 PM, Anonymous Anonymous said...

Are bat populations also on the decline as are most bird species? What a shame it would be not have bats around anymore. We live in a small town and everyone has bat houses set up in their yards, they are alot of fun to watch. I think I read somewhere that bats consume hundreds of insects each night, folks love having them in their backyards.

Allan Eldridge

At 3:08 PM, Anonymous Anonymous said...

I find it surprising that the bats did better when they heard highway noises than the noise of rattling reeds, which is something more natural in natures. Bats obviously survive quite well though so it seems they have learned to work around background noise and still find food successfully. How important is it that bats get human help to survive? I was unaware that this was even an issue.

-Julie Riley

At 9:06 PM, Anonymous Anonymous said...

The way I understand echolocation, bats emit noises at high frequencies, mostly outside the range of human ears. So I'm not sure how highway noise, and other man-made noise of low frequencies, would affect the bats hunting (besides being distracting I guess.)

-Jane de Verges

At 9:44 PM, Blogger PWH said...

The idea of being distracted by noise when the bats use echolocation is something that confuses me. Could reason for the differences in how well they located their food be because the highway noises all sound a like to a certain extent and the differences between different white noises is greater?

Ahmed Sandakli

At 10:05 PM, Anonymous Anonymous said...

I would be interesting in how the bats' success rates in hunting differ between a noisy environment and a quieter one. These scientists have shown that bats prefer to hunt in a quiet environment. But if they were forced to hunt in a noisy environment, how would the rate of prey captured/eaten compare? Does it truly interfere with their hunting, or is it just something unpleasent that that they could avoid if necessary?
-Corinne Delisle (3)

At 10:38 PM, Anonymous Anonymous said...

Good topic choice! I am wondering where the bats were taken from originally (if they were from a place near a highway). Also, in your article, what does it mean when it says "white noise"? Does the natural noises really interfere with the bats' hunting badly?

Alyson Paige

At 11:22 PM, Anonymous Anonymous said...

I am also very curious to know what environment these bats were originally taken from. It is rather peculiar that the sounds from their natural environment would distract them. At the same time, I'm not at all surprised that they were able to adapt quickly to the loud, unfamiliar sounds in the testing.

Posted by Sarah Moltzen

At 11:27 PM, Anonymous Anonymous said...

Bats use something similar to radar to navigate and orient themselves and their prey. Just as one can jam a radar, one can also jam a bat's senses. Although I am not too knowledgeable when it comes to bats, I do know a thing or two about sounds. I suggest that the different sounds introduced (white noise, highway and rattle of steel) have different sound frequencies and therefore wither pose or don't pose an interference to the bats' echo-location. I suggest that if the frequency of a noise is close to that of the signal sent by the bat, it might confuse the bat because it would perceive the artificial noise as his own signal returning from the object of prey.

Noam Pelleg

At 11:50 PM, Anonymous Anonymous said...

wow that picture really jumps out at you! it makes me wonder how bats can survive with noise pollution. not only near highways but other places.
-Matthew Sousa


Post a Comment

<< Home