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From: arf@gagme.chi.il.us (jack schmidling)
Newsgroups: sci.bio
Subject: BATS revisited
Message-ID: <1574@gagme.chi.il.us>
Date: 22 Jun 91 03:27:01 GMT
Organization: GAGME Public Access UNIX, Chicago, Illinois, USA
Lines: 47


 
 Article 4646 (45 more) in sci.bio:
 From: troach@netcom.COM (Tom Roach)
 Subject: Bat's sonar revisited
 
 >There is no doubt that the bat can catch insects on the wing, and there is a 
 fairly good presumption that it uses sound, and "chirped" sound at that, to 
 dothis....   For a bat, or anything else, to be able to distinguish a 10
 nanosecond differential in time of arrival of a sound wave is difficult
 for me to believe.
 
 
 ARF says:
 
 Two points of interest here.  First of all, for what it is worth, the 
 echo-location calls of bats are pulses of short duration and vary in 
 frequency and rep-rate as a function of distance to the target.
 
 The "chirps" one (a human) hears are socializing calls.  They are used to 
 find and identify young/parents, for courting and during grooming and play 
 time.
 
 Second point is that the vast majority of insect catches are made in the 
 inter-femoral membrane.  This is wing-like tissue streatching from hind leg 
 to leg on bats that have them.  It serves the purpose of a large net for the 
 ones that get away.  The bats pokes his head into the net to retreive the 
 captured prey while in flight.  The point being that if the resolution 
 requirement was based on a direct hit by the much smaller mouth, it was based 
 on a false assumption.
 
 >Anybody out there with more information, or better yet, an explanation
 to discount/explain anything I have said above?
 
 It is impossible to prove a negative but studies have been done in totally 
 dark rooms with wires from floor to ceiling, on one foot centers.  The bats 
 rarely hit the wires and echo clicking is continuous while the bats are in 
 flight.    I do not recall the species of bat but my experiments with 
 Eptesicus fuscus (Big Brown Bat) were not quite as dramatic.  They would 
 frequently run into random wires even with the lights on but never into 
 larger objects.  
 
 Whether they are doing something else, we will not know until we know.  
 However, we didn't know they were clicking until someone had the bright idea 
 to listen for sounds out of the human range.
 
 arf