View Full Version : Autumnwatch and the Bats

9th Oct 2011, 11:45
Was watching this programme on Friday night, and got thinking about bats and their echolocation, as one does:hmm:
Does anyone know if each bat uses a discreet frequency? 'cos if they don't then I could see some problems, like "oi you get away from MY lunch, I transmitted first"
On a saner note, if the Freqs are not discreet for each then how does one bat discriminate all the returns that he/she receives? Any ideas?
Regards, Den.

9th Oct 2011, 11:53
If you and a friend are walking down a dark road, both with torches - how do you tell what is in your beam of light from the objects in your friends beam?

You (and bats) have two ears for a reason (other than simple redundancy!). When an object makes a noise (even a reflected noise) your ears receive slightly different signals, in timing and amplitude, and your brain does the maths to determine that object's position. The original source of the sound doesn't matter.

tony draper
9th Oct 2011, 11:57
Plus they prevent yer hat from falling down over yer eyes.:)

9th Oct 2011, 12:06
Does anyone know if each bat uses a discreet frequency? 'cos if they don't then I could see some problems, like "oi you get away from MY lunch, I transmitted first"

Perhaps each bat squawk idents!

I am not sure if bats are cleared for surveillance radar approaches and as we know none of the them ever fly VFR!

Interesting question.


9th Oct 2011, 12:14
We had lots of bats around our place, but they've all
disappeared lately. Never see any at all now.
I reckon them and the sparrows have gone off to sunnier parts.

I think part of the problem is that all the old places that they
nested in have been knocked down and "Redeveloped".

I did read somewhere that they each have an individual "Voice",
but they can recognise others' voices.

9th Oct 2011, 12:22
You are near to my train of thought, I was wondering if they were encoding their own Tx's and could only Rx these.

I am not disputing your way of looking at the question, but if all the bats are transmitting and receiving on the same freq. then it doesn't matter who receives the info. or into which ear, they are all going to end up in a dogfight (batfight?) going for the same meal.
Regards, Den.

Krystal n chips
9th Oct 2011, 12:57
Any feul knows that bats had TCAS long before we ( not so clever ) humans came up with the idea...this explains why those that fly in and around the hovels garden...and are fascinating to watch...:ok:...manage to avoid hitting the tarpaulin and plastic sheeting that passes for ones abode....unlike the most stupid bird in the world, a pigeon ( well second, I suppose, after pheasants ) who left a perfect impression of itself after a CFIT incident....ones upstairs window to be precise.

west lakes
9th Oct 2011, 12:59
Never see any at all now

We had some flying around on Friday evening just as it was getting dark..

9th Oct 2011, 15:29
I'm sure there was a study a few years back which revealed that one species of bat here in the UK used a slightly different squeak in different parts of the country.

There is one kind of moth which not only has a coating on its wings to absorb the bat's sonar, but can also emit a jamming squeak of its own to spoof its main predator bat. Said bat, in turn, has evolved a staggered pulse repetition frequency to cope with that.

I would really like to know how my cat can occasionally catch bats....about 2 or three per Summer. My theory, as yet untested, is that she sits on the shed roof and lunges at the beasts as they zip through the gap between my house and next door.

9th Oct 2011, 15:34
Animal echolocation - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Animal_echolocation)

Read all about it in Wiki. I have and am no wiser! Seems the little b.....s are very clever.Use FM signals and CF signals ect. We are way behind.:(

9th Oct 2011, 18:27
I'll tell you one thing about bats. They don't like being peed upon ... A few years back I was in Dadaab, Eastern Kenya, and chose to use one of a line of newly built "long drop" toilets at a medical centre to just spend a penny. It just happened to be the one chosen by a bat colony as Chez Nous, they were all down in the deep concrete chamber having their afternoon nap, when yours truly proceeded to rain on their parade.

They didn't take it lying down (or upside down, perhaps), they swarmed up through the hole in the slab in a dense, flapping, squeaking cloud, startling me into a panic matching theirs. I flung the door open, zipper and modesty forgotten, and dashed out into the sunlit yard area, to be confronted by a crowd of locals having their best laugh of the day. My colleagues told me that only one cubicle was bat-infested, the locals knew this and avoided it. But when a Mzungu was seen to enter, anyone nearby stopped to watch the fun - well, there probably wasn't any telly out there ....

A year later at a very formal meeting in the Nairobi offices of the Posts and Telephones Department, the ice was well and truly broken by a Kenyan engineer relating my incident in great detail, with full mime actions, to the roomful around the conference table. I'm not quite sure what the wiggling of his little finger was meant to represent .... ;)

9th Oct 2011, 19:14
Mother-in-law definitely uses a discreet frequency, usually a loud screach.

Shame she doesn't hibernate somewhere for a few months!

9th Oct 2011, 19:36
Facinating animals but just hope they don't roost under your roof tiles or behind your shutters...'cos they poo and pee on everything.............

9th Oct 2011, 19:45
Bats?? Bats????

It's Kate Humble's tits I miss.

Can Michaela Strachan (http://www.google.co.uk/imgres?q=michaela+strachan&hl=en&sa=X&rlz=1R2ADRA_enGB425&biw=1024&bih=612&tbm=isch&prmd=imvnsuofd&tbnid=_aMFBnDrYJnp1M:&imgrefurl=http://woodystellycaps.********.com/2010/06/michaela-strachan-michaelas-wild.html&docid=WVHJ3S0J9KdIIM&w=828&h=828&ei=NeyRTtrONIKt8QOd_NgF&zoom=1&iact=hc&vpx=87&vpy=267&dur=94&hovh=225&hovw=225&tx=112&ty=166&page=9&tbnh=123&tbnw=123&start=143&ndsp=18&ved=1t:429,r:6,s:143) measure up?

9th Oct 2011, 20:14
Michaela all the way.......

Not that Kate isn't a lovely lass, but there's something about a girl with a fringe..:)

10th Oct 2011, 00:29
The Wiki article seems to answer most of your questions....

Either they use FM (chirp/spread-frequency), so each 'chirp' echo would sound different from those of nearby 'colleagues', or CF, and then they would be listening only to frequencies (doppler) close to their own 'pulse', which would vary between individuals.

Fascinating subject.


10th Oct 2011, 00:53
A lot of North American bat colonies have been wiped out by a fungal disease. It doesn't kill the bats directly but it leaves them too weak to survive hibernation. The last I read about it, scientists still didn't know the origin of the fungus. It is feared that it could lead to some species becoming extinct, according to what I read.

I was out the other evening when there were a couple catching insects over the fire pond behind my digs. They seemed to be doing okay, but of course it's only autumn.

However they do it I have never heard of a mid-air between two bats. It must be TCAS that they use, yes, unless they take turns doing ATC. Also, about the only way to catch them is with a 'mist net" which is made of very fine stuff that they cannot pick up on their sonar.

The word is 'discrete,' meaning 'distinct," by the way. Lots of people mix it up with 'discreet,' what my mother-in-law was not.

10th Oct 2011, 01:12
I have never heard of a mid-air between two bats. It must be TCAS that they use, yes, unless they take turns doing ATC.The NTSB (Night Time Safety for Bats) dealt with that a few million years ago.
They use AFR (Audio Flight Rules): listen, and be heard.


10th Oct 2011, 09:06
Thanks for the Wiki article Crippen, still doesn't answer the core question though.
How do bats of the same species, flying together, in a target rich environment avoid,
A.Overload of their own Rx's by neighbouring Tx's, that is assuming that all bats of the same species use the same freq. which the article suggests.
B. And how do they identify returns from their chosen lunch, and not returns from a pal who may be targeting a co-located snack?
Maybe, as Krystal and CristiaanJ suggest,they just have their own bubble of airspace that are not infringed by others.
Regards, Den.

Solid Rust Twotter
10th Oct 2011, 10:24
Same way you recognise your own voice perhaps?

10th Oct 2011, 12:53
If I recall correctly bats have both an echolocation frequency at around 60kHz and a 'chatter' frequency at 15-20kHz, so perhaps they warn off their friends "Oi, that moth's mine, gerroffit".

As a lad I used to spend time outside when the bats were flying (cf the meteor shower thread) and remember being able to hear the odd squeak.

These days we still have bats but I can't hear anything: I shall have to ask granddaughter to listen and see if she can hear them, might shut her up for a minute or two.


DX Wombat
10th Oct 2011, 15:54
Christiaan :ok: :D
A word of warning: NEVER pick up an injured or sick bat unless you are wearing bite-proof gloves as some bats, particularly Daubentons, carry the bat rabies virus - European Bat Lyssavirus (EBLV) which is lethal to humans.

10th Oct 2011, 17:12
Same way you recognise your own voice perhaps?I was going to suggest the same sort of thing... think of carrying on a conversation in a crowded room, where you 'pick out' the conversation because of differences in each voice.
We can't distinguish between bat's voices, but I would expect they can, even among the same species.

Question A: I would think that even in FM mode, it's still pulse, so there is a degree of 'time division multiplex'... And I've never seen bats operate in close formation, unlike swallows.
Still I suppose they would 'listen out' in case somebody else stumbles on a nice juicy swarm of bugs, and switches from 'search' to 'attack' mode.
Question B: I would think each target 'sounds' different to them. Many years ago, I've played with a small 3cm CW radar, with just Doppler audio output, and even I ended up being able to distinguish different 'targets', just from the sound.

IIRC the bats we could hear when we were young (...) were using 'long range search' mode in the 15 to 20 kHz range. And yes, ask your grand-daughter!

Never seen an injured, sick or dead bat yet around here, so thanks for the warning. I might not have thought of that.


10th Oct 2011, 23:40
DXW and ChristiaanJ - If you refer back to my post #11, it wouldn't be so much my hands being bitten by the bats that I would have been concerned about, as .... :eek:

11th Oct 2011, 00:16
DXW and ChristiaanJ - If you refer back to my post #11, it wouldn't be so much my hands being bitten by the bats that I would have been concerned about, as .... :eek:Yes, 603DX, we got that point..... :}
Here in 'civilised' Europe we'd be unlikely to find ourselves in the same situation.
But... we might still be tempted to 'save' an injured bat, if we ever came across one.
In that context, DXW's warning made good sense to me :ok:.


Loose rivets
11th Oct 2011, 00:46
Yes, much more aware of rabies since living in Texas. Funny thing...well, not at all funny really. Stopped to help a sickly possum. someone had given him some cat food, but when I offered him some water, he went totally apeshit. Now that's not a word I'd normally use, but it's the most descriptive. I backed away a bit sharpish.

Could it be the hydrophobia is really real?

Bats. I'll take more care now, but when I was about 25, I had a bat flying about in the old redbrick house we had at Walton on the Naze. It had such subsidence, that the door frame left a 1" gap tapering to nowt at one side. the bat flew through that gap and hung on my bedroom curtain. He= or she - was fine. Let me pull its wings open and show it to the Rivetess. I took it to the door and it flew off.

11th Oct 2011, 01:23
A word of warning: NEVER pick up an injured or sick bat unless you are wearing bite-proof gloves as some bats, particularly Daubentons, carry the bat rabies virus - European Bat Lyssavirus (EBLV) which is lethal to humans.
Quite so. Dununder, they carry Lyssavirus and Hendra virus, both very nasty.

Many years ago, I caught a bat that had taken up residence between a door and its frame. Put it in a container and daughter took it to kindy for show & tell, where it was patted etc. It didn't bite anyone, (not that they need to to pass on Hendra) but I certainly wouldn't have if we'd known what we know now.

11th Oct 2011, 01:28
In the UK you need a licence to handle bats, so it is illegal to pick one up or touch it (though I have done so when I've found them hanging in the curtains having flown in through an open window).

It's wisest to wear sturdy gardening gloves and even cover the creature with a towel (though the temptation to examine their 'wings' is irresistible).

A healthy bat can take-off from the ground, but may prefer to 'roost' on a tree-trunk during daylight.

11th Oct 2011, 10:30
My old cat would occasionally catch one, apparently when it came too low after a moth. As far as rabies is concerned, tehre was a guy in Scotland who died from it after a bat bite - that was two or three years ago. It was a Scottish bat, he was not in furrin parts. Well, that depends on how you view Scotland.

11th Oct 2011, 11:27
I remember once playing tennis under floodlights in Rhodesia. I was serving, threw up the ball which collided with a bat. Picked up the bat and put it on the netting around the court where it flew off after a minute or so.

Don't know if the bat thought the ball was a big insect or it was simply a collision.

11th Oct 2011, 15:31
My favourite bat yarn came from David Attenborough.

Many will remember him standing in the mouth of a cave with thousands of bats streaming past him, and saying "Thanks to their amazing radar they all manage to avoid me".

In an interview sometime later he said that no sooner had the words been uttered and the camera switched off, one flew smack into his face.

11th Oct 2011, 15:59
Maybe it was trying to eat him, large RCS, big bat was it? :)
regards, Den.

11th Oct 2011, 21:27
I don't know about individuals, but different bat species have very different frequencies and sound signatures.

I did a few years ago an autumn bat excursion from a local nature center. The guide had a receiver (basically a microphone and a sort of modulator) that brought the bat screeches down to audible-to-humans frequency. And the guide could tell (in the quite dark place) the species before they even approached close enough to be seen. With a few hundred Euro, one can buy such a gear.

DX Wombat
11th Oct 2011, 23:25
With a few hundred Euro, one can buy such a gear. And with an Amateur Radio Licence you can probably make one for far less. ;)

11th Oct 2011, 23:51
I think the frequency depends on the type of bat.

Our local walk (Lymm Dam) have a "bat hunt" (they don't actually hunt the bat), each summer, the wardens take out bat recievers, which convert the bats radar into human audible sounds.


The creaking sound turns into a pharting sound when they catch an insect.

Fascinating stuff, thousands of the little beggars.

DX Wombat
12th Oct 2011, 00:13
There are lots of the little perishers here too - St Ives, Bingley (http://www.visitbradford.com/thedms.asp?dms=13&venue=2180211) and their friends down the road (http://www.yorkshirepost.co.uk/news/around-yorkshire/local-stories/why_bats_rule_the_roost_at_bridge_of_motorists_sighs_1_23044 22)caused no end of traffic chaos for months on end.

12th Oct 2011, 00:19
They're a little difficult to see here,but there were thousands of 'em

IMAG0018 - YouTube

12th Oct 2011, 08:47
how modulating the frequency alters the bats perception ,imagine the bat hearing the following video. The distance from the bat has a relationship to a different ball depending on the sweeping frequency.( I think)


12th Oct 2011, 12:35
Here is a video on a young deaf boy, who's eyes were removed (due cancer) who uses echolocation to get about. That's not that unusual in the blind community - but this lad rollerblades, rides bicycles and plays basketball all using echolocation!

Extraordinary People - The boy who sees without eyes [1/5] - YouTube


12th Oct 2011, 13:10
One morning a couple of years ago I found a bat asleep hanging in the hallway. Phoned the RSPCA who put me in contact with a bat lady. She told me how to set the bat free and said I should wear soft gloves to handle it. I assumed this was to avoid damage to the bat but no mention was made of wearing thick gloves to guard against bites. The bat remained comatose during the procedure but made a sharp exit when darkness fell.