0 comments on “B is for Bat Echolocation”

B is for Bat Echolocation

Microbat Photo by Neal Foster

By Jonathan Farrow from The Thoughtful Pharaoh

Ever wish you could see in the dark?  It would make life a bit easier.  No more tripping over clutter on the ground or feeling walls for a switch.  Humans rely quite heavily on their sight, but some animals can make do by illuminating their surroundings with sound.

Bats are just such an animal. ¬†They belong to a privileged group of organisms including toothed whales (like sperm whales, dolphins, and killer whales) and shrews that use sound to see the world. ¬†By listening for the reflections of their¬†high-frequency clicks, bats¬†are able to build up an accurate picture of the world around them. ¬†The clicks are often too high for humans to hear, sometimes reaching as high as 110 kHz (human hearing generally goes¬†from 20Hz-20kHz). ¬†This amazing superpower is called echolocation but not all bats have it. ¬†Most microbats (usually small, insect-eating, with proportionally large ears) can echolocate using their throat to produce clicks, while megabats (larger, fruit-eating, with large eyes) usually can’t. ¬†Like most rules in biology, though, these distinctions aren’t¬†universal. ¬†Some megabats have evolved¬†echolocation by way of specialized nose structures and others are smaller than big microbats.

An example of a Megabat, waiting for Comissioner Gordon to turn on the signal. Photo by Gerwin Sturm
An example of a megabat, waiting for Comissioner Gordon to turn on the signal.
Photo by Gerwin Sturm
This little microbat can't wait to be free! Photo by Neal Foster
This little microbat can’t wait to be free!
Photo by Neal Foster

So now that you’ve been acquainted with the notion of echolocation and the bat family tree, let’s start talking about some neat things that bats can do with their special ability.

Jamming

Since echolocation is dependent on a bat receiving and interpreting the reflections of sound, it is particularly¬†susceptible to interference. ¬†The biggest source of interference is the bat itself. ¬†Bats produce some of the loudest sounds in nature and have some of the most sensitive ears to register the reflections that come back hundreds of times quieter. ¬†Imagine revving up¬†a Harley Davidson and putting a traffic cone on your ear to hear someone whispering across the room. ¬†It would probably hurt if you did those things at the same time. ¬†You’d be too rattled by the revving to be able to listen to the whisper. ¬†Bats avoid this by temporarily disconnecting their ears as they shriek, then quickly reconnecting them in time to hear the echo.

One particular species of bat, the Mexican free-tailed bat (Tadarida brasiliensis), has been recently observed messing with its competitors’ signals. ¬†By emitting a special signal right when another bat is about to catch an insect, the bats make each other miss. ¬†It’s the bat equivalent of yelling “PSYCH!” when someone is about to shoot a free-throw. ¬†Unlike the obnoxious friend though, the bat version¬†actually works. ¬†The bats’ success rate drops by about 80%. ¬†It’s such an effective strategy that two bats will even hang out near each other, jamming each others’ signals every time one swoops in for a bug, until someone gives up.

Adapting

The same species of bat that jams also lives in close proximity to natural gas fields in New Mexico.  Some of the rigs have compressors that emit a constant, loud noise that can interfere with echolocation calls.  For the Mexican free-tailed bats, whose normal calls fall within the same frequency range as the compressors, the loud wells are avoided when possible.  The bats have also begun to change their calls, making them longer and in a more restricted range of frequencies.  This strategy would make the calls more easily distinguishable from the background din and marks the first time human-made noise has been shown to interfere with bat life.

Sneaking

We know that humans can’t hear a lot of what the bats are “saying” when they are building up a sonar picture because our ears aren’t sensitive to the right frequencies. ¬†This makes sense because, for the vast majority of humans, it really doesn’t matter what the bats are saying. ¬†It’s a whole¬†other issue if you’re a moth about to be eaten. ¬†There’s a lot of (evolutionary) pressure to hear the bats coming in order to avoid getting eaten. ¬†Some noctuids, a rather large family of moths, have evolved bat-sensing ears that warn the insect of impending disaster. ¬†If the bat is far enough away, the moth will make a break for it, otherwise it will just start flying erratically in random directions to try and make the bat miss. ¬†The Pallas long-tongue bat (Glossophaga soricina) still manages to get a meal by using only ultra-high-frequency, low intensity calls to find moths and by going silent on approach. ¬†This stealth mode doesn’t trip the moth’s defences.

Stealth bats.  Also happen to have the fastest metabolism of any known mammal. Photo by Ryan Somma
Stealth bats. Also happen to have the fastest metabolism of any known mammal.
Photo by Ryan Somma

For more information on echolocation and bats, check out:

The Bat Conservation Trust, a UK charity devoted to all things bat

This Scientific American article about how echolocation works

This study about Mexican free-tailed bat jamming

This study about Mexican free-tailed bat adapting

This study about Pallas long-tongue bat sneaking

0 comments on “Want to adopt a bat with Avon Bat Group?”

Want to adopt a bat with Avon Bat Group?

Microbat Photo by Neal Foster

A BIG thank you to Kiri and Stuart from the Avon Bat Group for coming to Enter the Bat Cave and showing off the beautiful little animals they have in their care. Everyone really enjoyed getting up close and personal with an animal that is so rarely seen by the general public.

Stuart and Kiri with their bats and Bish the bear from Bristol Improv Theatre
Stuart and Kiri with their bats and Bish the Bear from Bristol Improv Theatre

If you are interested in supporting Avon Bat Group, adopting a bat, or just want to know more about your new favourite mammal; you can find more information on their website at www.avonbatgroup.org.uk, or like their facebook page for regular updates. We hope that after all you learnt during the evening, you can really appreciate how important their work is.

Thank you to everyone who came last night, we hope you had a great evening! Keep an eye on the website for more information about our next event and for another of Antony’s excellent infographics about Enter the Bat Cave.

0 comments on “ENTER THE BAT CAVE Ft. Batwoman Heather Nichol”

ENTER THE BAT CAVE Ft. Batwoman Heather Nichol

Plunge into the depths of one of Bristol‚Äôs darkest bat caves ‚Äď a place where the echoes of lost souls linger and haunt the footsteps of all those who enter. Fleeting silhouettes of winged creatures lay claim to these walls, and the stench of guano weighs heavy on the air‚Ķ

OK, so in reality we just turned off all the lights in the Bristol Improv Theatre, and the Rising Ape team forgot to wash, but bear with us for a moment. Rising Ape returns with a night of bat-themed madness. Bring a team and stretch your wings in the quiz. You better know your long ears from your short snouts, your Dracula from your Orlok, and your Slazenger from your Gunn & Moore. But as bat researchers stuck in a terrifying cave, we don’t expect you to just sit there all night. Be prepared to get up close and personal, untangling these creature’s fascinating secrets for yourselves with help from some special guests. To conclude the night’s eerie proceedings, real-life Batwoman Heather Nichol will share her personal journey into the world of bats.

Tickets available at http://improvtheatre.net/calendar/enter-the-bat-cave/

Tickets also available on the door.

Enter the Bat Cave... there is no exit.
Enter the Bat Cave… there is no exit.

More about Heather Nichol: Heather has been involved in bat conservation for the past 5 years. She was first introduced to the world of bats during her undergraduate degree at the University of Leeds, and has since taken part in various conservation projects, including a project that discovered the first know breeding colony of Alcathoe bats in the UK. Heather has just completed a Masters by Research at the University of Bristol studying one of the hot topics in ecology at moment: bat fatalities in wind farms in Britain.