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From: davidh@uhunix1.uhcc.Hawaii.Edu (David A. Helweg)
Newsgroups: sci.bio,talk.environment
Subject: Re: Bats by a Mile
Summary: read some 20th century literature
Message-ID: <13099@uhccux.uhcc.Hawaii.Edu>
Date: 18 May 91 07:41:53 GMT
References: <1991May17.044756.26698@ddsw1.MCS.COM>
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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