Xref: utzoo sci.bio:993 sci.misc:1004 rec.birds:476
Path: utzoo!mnetor!uunet!wucs1!wucs2!slustl!slu70!guy
From: guy@slu70.UUCP (Guy M. Smith)
Newsgroups: sci.bio,sci.misc,rec.birds
Subject: Re: animals and Earth's magnetic reversal
Message-ID: <112@slu70.UUCP>
Date: 16 Mar 88 18:46:29 GMT
References: <7387@ihlpa.ATT.COM>
Organization: St. Louis Univ., St. Louis, MO
Lines: 17
Summary: maybe

In article <7387@ihlpa.ATT.COM>, cutler@ihlpa.ATT.COM (Herber) writes:
> 
> the earth has reversed it's magnetic polarity many time is the past.
>  Has anyone given thought on the resulting effect this might have on
> animals, migratory birds in particular, that use this field for 
The reversals of the field are well documented. They are not instantaneous
by the way, best estimates are that reversals take something like
five to ten thousand years during which the field is much more complex
than at present (in short, no simply defined north and south poles).
See "The Earth's Magnetic Field" (Merrill and McElhinny. I haven't
followed the magnetic navigation of animals lately but my recollection
is that even those animals that are field sensitive only use the field
as a secondary mechanism (e.g., during cloudy weather). As such,
reversals probably wouldn't have much effect. Attempts to correlate
reversals with mass extinctions have not been successful. For what
it's worth, I've got a PhD in this field and have been an active
researcher for several years.