
Bats slam into buildings because they can't 'see' them - TrickyRick
http://www.nature.com/news/bats-slam-into-buildings-because-they-can-t-see-them-1.22583
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theoh
This reminded me of (humor)
[http://www.mjt.org/exhibits/foundation_collections/depmori/d...](http://www.mjt.org/exhibits/foundation_collections/depmori/depmori.htm)

"The key idea in the Griffith hypothesis was that as the Myotis lucifugus
emission increased in frequency, the emission actually crossed the thresholds
from the extreme ultraviolet into the X-ray, thereby allowing the bat to fly
unharmed through solid objects."

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swighton
Reminds me of a an anecdote about the F-117 Nighthawk which was the first
stealth airplane nearly invisible to radar. Apparently the engineers working
on it would come into the airplane hangers to find many dead bats as it was
also invisible to sonar.

Interestingly enough this made the engineers realize the stealth technology
also could work for submarines which led to the IX-529 Sea Shadow stealth
ship.

~~~
sjtgraham
The bats died because the radar absorbent material used on the F-117A was
highly toxic.

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mwerd
Poor bats. They also get their lungs exploded by the pressure differences
created near wind turbines: [https://www.wind-watch.org/news/2016/09/27/wind-
turbines-are...](https://www.wind-watch.org/news/2016/09/27/wind-turbines-are-
causing-bats-lungs-to-explode/)

~~~
Retric
Meh, a 5 Mega Watt wind turbine kills less wildlife than the average outdoor
cat.

~~~
trhway
turbines and cats put different selective pressure on the prey population -
cats kill weak, ill, etc. thus improving the overall quality of the population
where is turbine kills are probably spread uniformly and even may be skewed
toward healthy active animals.

~~~
reportingsjr
How did you come to this conclusion? This is so unbelievable wrong I don't
even know where to begin.

Cats do not just kill weak animals. They kill strong and healthy animals at an
alarming rate. Cats have been responsible for at least 33 island animal
extinctions in recent/recorded times [0].

[0]
[https://www.nature.com/articles/ncomms2380](https://www.nature.com/articles/ncomms2380)

~~~
trhway
There are 10B birds born per year in the US. In Nature pretty much everything
is a food for the next level in the food chain, and there is no family&friends
funerals. The more weak/ill/old - the higher probability to become predator's
dinner. We don't have dead old birds littering the streets of cities. Somebody
takes care about it.

And as you see from your own link cats mostly eat smalls mammals. Around
humans it is mice and rats mostly. Rats do enjoy bird eggs and there is no
protection here, until of course somebody takes care about the rats, like for
example cats do.

As result cats do positive service to the birds population. The population
which somehow manages to survive the urban and agricultural development - the
main dangers for the wildlife causing population decimation and extinctions.

And island extinctions, really? So the cats brought by humans should have just
committed suicide by starving themselves? Of course things can easily go wrong
in any small system when the system gets severe kick from outside. And humans
do just that to various eco-systems. How many species on various islands got
extinct once humans reached those islands?

~~~
Retric
That's an overly simplified model to the point of incorrectness. A Lion wants
a sick / old / _or young_ water buffalo because it's less dangerous. However,
a house cat does not really care about a mouse or bird.

If you look at mice reproduction they mostly get eaten before adulthood. Young
healthy animals are often preferred prey because they are easy targets.

Finally, predators regularly drive species to extinction, which is a large
part of why the vast majority of species to ever exist are not currently
around.

TLDR; Cat's need 8 adult mice a day if that's all they are eating and they
really can't afford to just look for sick animals. They easily hunt healthy
adult birds, some baby rabbits, or other small animals.

~~~
trhway
Where do you think tens of billions of old mice/rats that are to die yearly
are supposed to go, especially in developed areas where there are not many
other predators?

In predation even without any specific choice by the predator, the resulting
prey is naturally skewed toward weak/sick/old, ie the ones who is slower, has
lower attention/senses, etc. Until some age the young are naturally on the
weakest side and not surprisingly may fell prey a lot. Such filtration results
in more healthy/agile/stronger adult population.

~~~
Retric
Relative size makes a big difference. The most extreme version of this is
krill, as a blue whale really does not care about the fitness of the millions
it needs to eat.

What your missing is most mice don't reproduce. The average litter is 6-8 and
mice can have multiple litters per year. So, mice basically never reach old
age.

The selective pressure has more to do with caution because a completely heathy
mouse can't out run a cat / owl etc.

Put another way cats rub at up to 48 Km/h mice 13 Km/h. Thus, 'fitness' has
little to do with athletic prowess.

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grondilu
That made me wonder how bats see water surfaces. Though I suppose not seeing
them is less of a problem since they're not vertical :P

~~~
ethomson
The post explains this: they don't. Standing water exhibits the same behavior
as reflectiveless flat surfaces.

When they fly over a space and "see" nothing beneath them, they interpret this
emptiness as a flat, smooth body of water.

Thus the only real problem here is that for flat horizontal surfaces that
aren't water, the bats will try to drink from them.

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Isamu
I had read this as Bots slamming into buildings, and was looking for a
discussion of lidar and stereo vision systems.

But won't lidar have the same issue, with a clean glass surface? Similar with
stereo vision - if there are no features at the surface to correlate.

~~~
emeijer
Vision based on visible light doesn't suffer from the problem in the same way
as echolocation or lidar, since it is not dependant on observing signals
emitted by the observer. I guess very smooth surfaces might act as mirrors,
which will probably bring it's own set of difficulties for machines.
Anecdotally, I can say my own stereo vision doesn't have big difficulties with
most smooth surfaces though :)

~~~
bighi
But bats also use vision based on visible light. I haven't read the article
yet, but do they explain about why the bat wouldn't see the building with its
eyes?

~~~
Raphmedia
"researchers can rule out the possibility that the bats were visually
confused, because the experiments were done under infrared light, which bats
can't see, and so they would have been relying entirely on echolocation."

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peterwwillis
TIL Some Hawkmoths shoot ultrasound from their junk to thwart bat attacks.
[http://www.pnas.org/content/112/20/6407.full.pdf](http://www.pnas.org/content/112/20/6407.full.pdf)

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amelius
I wonder how bats perceive the AT&T "Batman Building" in Nashville, TN.

[https://en.wikipedia.org/wiki/AT%26T_Building_(Nashville)](https://en.wikipedia.org/wiki/AT%26T_Building_\(Nashville\))

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stcredzero
I hope someone doesn't use this as inspiration for an exploit against LIDAR.
On second thought, I hope people do start working on an exploit, so engineers
can get on with hardening systems against it!

~~~
totalZero
The use cases I know of for lidar don't usually include a glancing reflection
off a large flat surface.

~~~
stcredzero
Colliding with a large angled piece of sheet material in the middle of a
roadway doesn't sound pleasant.

~~~
LeifCarrotson
While I agree that the sensor systems should image just about anything you can
imagine, wouldn't a large angled reflective sheet produce a shadow that could
be distinguished from normal road surfaces and avoided?

~~~
stcredzero
That's a good 1st cut. But if we review the prior art -- namely stage magic's
tricks with mirrors -- what's to stop someone from putting something in the
region of the reflected image that would be expected by the driving AI? So, if
what's expected are bushes in the background, why not aim the mirror at other
bushes at the right distance?

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sailfast
Interesting hypothetical to track bat evolution in urban areas over time to
determine if selection is occurring for bats whose sonar is more finely
attuned for detecting diffused returns as actual signal for skyscrapers or,
for that matter, improved actual sight to avoid the buildings in the first
place.

~~~
Filligree
Bats already have very good vision. They just can't see well in the dark.

~~~
pvaldes
Is probably more a case of blinded by electric lights here.

