Mango Trees and Bat Droppings-Help!

First tell us which of these three you can most readily live without: mosquitos, mangos, or bats?

Once we know your answer you'll probably get some interesting 'solutions.' As an example if you say bats then I would tell you about a trick someone told me last week where you use the aluminum or steel lids from your large outdoor garbage cans and set them up horizontally attached to strategic parts of your house (e.g., eaves.) It messes with the bats radar and they eventually end up flying into them. Of course you have to scoop up the bat bodies from time to time and live with having mangos and mosquitos.

Geez, GoodToGo, this is tough! I certainly can live without mosquitoes, but this stuff all over my house is really disgusting. I did some research and found out it's not droppings. The bats eat the mango and then they spit out the pulp, and skin. I wonder if I hung something smaller, like pot and pan lids, maybe that would mess them up enough to go eat the neighbor's mangoes, but I wouldn't have to scoop up little bat bodies. My cat already takes care of our quota of dead things.

I emailed my brother-in-law, who is a mammologist. He didn't have any answers for me, but he was going to contact a colleague who, believe it or not, specializes in Caribbean Bats.

What a cool topic! I'm trying to imagine this discussion ever coming up in Virginia..... ahhh, USVI. Someone should put this one in a book!

Hi Juanita,

I'm dying to hear what your brother-in-law's colleague says... any news?

In some areas of the world hawks attack/eat bats. I don't know if there are hawks in USVI that do this, but if so I wonder if you could put a decoy hawk in the tree or on your roof.

And, I wonder if there is an easier answer. He is an engineer's approach to this:
- bats use sound waves to navigate and spot prey
- they transmit sound waves and then receive the bounced signals to determine angle and range to the target
- I don't know the frequency that they use, but I suspect that it's near to our hearing range (obviously not near enough that we hear it). We could find this out through google.
- I'd be tempted to try to jam their signals similar to radar jamming.
- a simple stereo system with a microphone; put the speakers pointing out the window (or near/in the trees)
- the microphone picks up their sounds
- the stereo plays it back to them.
- the bats either crash into your speaker (they think it's their bounced signal).
- or, they just get confused by their bounced signals in the presence of these other similar signals and go away.

BTW, the trash can lid idea is effectively doing the same thing:
- the trash can lid is bouncing their signals around
- the lid is big enough to bounce a big signal back
- you need the lids in various locations to pick up the bat transmissions coming from various angles, and to create bounced signals from various locations.

Obviously the bats are able to hunt in trees and around other bats, houses, cars, etc. So, their ability to discriminate between good and bad bounced signals is pretty good (having two ears they can probably look at a narrow angle). But, that's why I think a stereo system might be better. It might be equivalent to just screaming back into their little ears... the annoyance factor might be really high for them.

If you want to keep the bats around, I wonder if you could spray the mangos with a liquid that bats don't like but wouldn't poison the mangos (soap, dog apple bitter, etc). I don't know what mango trees look like, so I don't know how practical this is.

The speakers are an interesting idea but I suspect with WAPA rates it won't be cost effective to run them for several hours per night - not sure though.

The tree is hugh, so just the physical logistics of trying to spray it is daunting. Speakers probably aren't a good idea. I have tenants who might not appreciate it.
The bat specialist didn't have any advice for me. Said my question was a first for him.
The good news is they seem to have stopped spitting on the house. Our maintenance man has been picking the mangoes as soon as they start to turn red/yellow. I just looked at the tree, and there isn't anything left that looks anywhere near ripe. That's probably the answer.

OK, so much for the speaker idea... I did a little research:
- bats talk and listen in the 25kHz to 120 kHz range
- that's right... that's WAY above our frequency range

- the good news is that your neighbors would never hear it.
- the bad news is that your stereo system would never be able to generate the signals
- the microphone, amp and speakers would be mighty expensive (I think)

- BTW, if you're interested in understanding a little bit about bat signals, see:
http://www.ploscompbiol.org/article/info:doi%2F10.1371%2Fjournal.pcbi.1000032
- as an engineer that has dealt with radars for the last 15 years, I can tell you that I only understood maybe 30% of this on first glance, so don't feel bad if this all seems like Greek. But I think you can see that they are very sophisticated little buggers.

- but I learned that you could cover your mangos with felt and they would be invisible to the little fruit attacking dive bombers. Felt's fuzzyiness (how about that for a technical term) absorbs the bat's 0.3 - 1.5 cm wavelength signals and therefore don't bounce anything back. Granted, given a huge tree, this is probably not very practical. And your neighbors would think you were nuts. Plus, the expense might be getting a bit out of hand.

- I'm still liking the trash can lid idea, if you find you need to do something in the future. I think metal/aluminum trash can lids would be better than plastic. I think you would like one lid for every few cubic meters of volume (10-20 for a large tree?). Hang each of them from a single string so that each can swing and rotate in a breeze. Do the bats only show up over a short ripening season? In other words do you only need these up for a few weeks of the year?