troach@netcom.COM (Tom Roach) (06/14/91)
I have given some though to the interesting postings on sonar capabilities of bats I read recently. In at least one posting there were claims of bats being able to distinguish "temporal" differences in the 10 nanosecond range. I know little about bat's sonar and just a bit about human radar. Still I would question any such claims. 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 do this. 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. There would have to be an incredible lack of "noise" in the signal, given the speed of sound, for it to make useful phase comparisons at this level. Also even if it could resolve phase differences this accurately, such information apparently must be transformed into something that results in changes in wing attitude and even more likely, the content of its "chirp", before such information would result in actions leading to the bat catching the insect in its mouth. I am also thinking that the speed of nerve impulses and the physical changes in wing shape, angle or whatever are far too slow to profit from such incredible resolution, even if it existed. If this is the case, then evolution would be unlikely to result in changes which would generate such "overkill". Sharks apparently use a combination of magnetic, aural, and visual information to capture prey. Has any work been done to see if the bat has additional sensors, or uses multiple sensory systems in catching insects? Anybody out there with more information, or better yet, an explanation to discount/explain anything I have said above? Tom Roach