monarchs in New Zealand

Dr. James Adams jadams at
Thu Apr 16 08:51:50 EDT 1998

Ken Phillip wrote:

> 	James Adams suggested that if Monarches migrate from the North
> Island to the South Island of New Zealand, that would indicate magnetic
> rather than solar cues are used.
> 	That is not a _necessary_ conclusion from the data, if what is
> meant is that all Monarchs migrate to the south to hibernate. Remember
> that western US Monarchs migrate towards the coast, which for some
> means going west. Whether solar cues, or magnetic field cues, are being
> used is not ipso facto obvious from the mere fact of migration.

Ken is, of course, correct in part.  I was using the fact that the vast 
majority of Monarchs have a general north-south direction of 
migration.  Heck, even here in the SE U.S., when the Monarchs come 
through in the fall they are, as you might expect, not flying 
directly south but distinctively SW (though it is still not known 
whether the ones that come through N. Georgia actually end up in 
Mexico).  And, the Monarchs in New Zealand, assuming they got there 
naturally, would have come from some of the Western U.S. populations, 
so Ken's argument is important from this respect as well.  All I was 
trying to point out was, assuming that the Monarchs actually *do* 
move from the North Island to South Island, it that they would have 
had to chose a direction to fly *initially*.  There would have been 
no previous "knowledge" of an *appropriate* overwintering site on the 
South Island.  I was not trying to say that magnetic cues would be 
the only ones in use here, simply that it would have been a mechanism 
Monarchs *could have used* in getting from the North to South Island, 
similar to a mechanism that *could be used* for the vast majority of 
naturally occuring Monarchs in the states.  It makes for a nice "easy" 
explanation, one that could very easily be wrong!!  


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