arf@ddsw1.MCS.COM (Jack Schmidling) (05/17/91)
Article 4431 (22 more) in sci.bio:
From: mll@hpfcso.FC.HP.COM (Mark Luce)
Subject: Sonar: Bats vs. Dolphins vs. Humans
> I am interested in any comparisons of the sonar capabilities of bats,
dolphins, and humans (human technology, of course!). In particular, I have
heard the claim that bats and/or dolphins have certain sonar capabilities
which we have not as yet been able to duplicate technologically. Is there
any truth to this, or is this just another modern folk myth?
----------
ARF says:
Bats win by a wide margin. In gross terms, electronic sonar can barely
detect a foot long fish. A dolphin can find a golf ball with difficulty
after much forced training. Bats, on the other hand, would starve to death
if they could not pursue and capture thousands of mosquito sized insects, on
the wing, every night.
What gives bats the edge over dolphins is a much higher frequency.
Bats operate from audio to about 100 khz. They alter not only the frequency
but the rep rate as they close on the target to maximize resolution.
Dolphins operate in the human audio range so the amount of data (resolution)
is much less but their normal food is much larger than insects. High
frequency would also be absorbed much faster in water so the range would be
more limited.
The above of course, only applies to insectivorous bats. Many fruit eating
bats have no echo-location capabilities at all.
arf
dean2@garnet.berkeley.edu (Dean Pentcheff) (05/18/91)
In article <1991May17.044756.26698@ddsw1.MCS.COM> arf@ddsw1.MCS.COM (Jack Schmidling) writes: > Subject: Sonar: Bats vs. Dolphins vs. Humans > Bats win by a wide margin.... > What gives bats the edge over dolphins is a much higher frequency.... Wouldn't the speed of sound in the medium have some effect? Sound is _much_ faster in water than in air. Wouldn't that make it much more difficult to measure distances by timing sound echos? -Dean -- Dean Pentcheff (dean2@garnet.berkeley.edu) Department of Integrative Biology, University of California, Berkeley CA 94720
davidh@uhunix1.uhcc.Hawaii.Edu (David A. Helweg) (05/18/91)
In article <1991May17.044756.26698@ddsw1.MCS.COM> arf@ddsw1.MCS.COM (Jack Schmidling) writes: > ARF says: > > Bats win by a wide margin. In gross terms, electronic sonar can barely > detect a foot long fish. A dolphin can find a golf ball with difficulty > after much forced training. Bats, on the other hand, would starve to death have at look at P.E. Nachtigall's chapter "Odontocete echolocation performance on object size, shape and material." in Busnel & Fish _Animal Sonar Systems_ Bottlenosed dolphins can detect wires down to a minimum diameter of .035 cm, and discriminate among targets that vary in thickness by 0.1 cm. > What gives bats the edge over dolphins is a much higher frequency. > Bats operate from audio to about 100 khz. They alter not only the frequency > but the rep rate as they close on the target to maximize resolution. > Dolphins operate in the human audio range so the amount of data (resolution) where did you get this information? Dolphin *whistles* are audible to humans, as is the envelope of both bat and dolphin click trains. Dolphins show adaptive control over click parameters such as peak frequency. In noisy waters (like Hawaii) they tend to shift the peak upward from about 60 to 120 kHz. Bats and Odontocetes have very different echolocation "styles." Bats tend to emit narrow-bandwidth, long-duration FM signals. They probably localize and capture prey using Doppler. Their pulses are not as well-suited for ranging targets as they are for determining velocity. In contrast, dolphins emit broadband, extremely short duration clicks. Their clicks are extremely well- suited for determining target range (by click-echo timing) but aren't really hot for doing velocity. You are right in one (important!) regard -- some prey species of bats have evolved fairly sophisticated "anti-bat" behaviors, such as asynchronous wing beats, diving flights, and even "radar jamming" sound emitted by the moths. No one is sure whether dolphins and their prey species have coevolved to this degree. But the reflective surfaces within fish (eg, swim bladders) are small relative to the size of the fish, so dolphins are doing some pretty decent detection themselves. can you tell I'm a dolphin afficianado? ;-) dah
pamela@bu-bio.bu.edu (Pamela Hall) (05/21/91)
In article <1991May17.044756.26698@ddsw1.MCS.COM> arf@ddsw1.MCS.COM (Jack Schmidling) writes: > > The above of course, only applies to insectivorous bats. Many fruit eating > bats have no echo-location capabilities at all. > > arf > > Just thought you might like to know that most species of bats are not insectivorous, most are fruit, flower and/or nectar eaters. Temperate bat species are almost all (I not sure if it is truly all species) are insectivorous while many more tropical species are non-insectivorous and as most species of bat are tropical, I think this puts insectivorous bats as a minority. Also vision is well developed in old world fruit bats (members of the Megachiroptera?), but the other order (Microchiroptera) are largely, though not exclusively, echolocating species. I also believe that this order has many more species than the Megachiroptera. In the neotropics, Microchiroptera dominate, (maybe even being the only order of bats in the neotropics?), while in the old world tropics both Microchiroptera and Megachiroptera exist. At some point in the not too distant past (maybe 2-3 years ago, in Science) researchers concluded that the Megachiroptera species were actually more closely related to Primates than to Microchiropteran bats! How about that, true flying primates!!! I hope I haven't just told you something you are much better informed about than I! Pamela Hall