The article Paul warned us about (Matanzas en Michoacan)

[Paul Cherubini]

Doug Dawn wrote:
 
> Tomorrows NY Times covers the preliminary info,
> Storm in Mexico Devastates Monarch Butterfly Colonies

Thanks for the article Doug. I'm not worried about the butterfly mortality.
Here's why:

Dr. Orley (Chip) Taylor wrote:

> A report (Brower, et al., in prep; released for publication on 
> 12 February 2002) of the deaths of tens of millions of monarchs 
> at the two largest monarch overwintering sites in Mexico once 
> again confirms the long held view that it is the overwintering
> sites that hold the key to the continuation of the monarch
> migration in eastern North America.

I disagree with Dr. Taylor.  There just has been no good correlation over
the years between the numbers of monarchs that survive the winter in
Mexico to return to the USA and the size of the subsequent fall migration 
six months later.

Take the winter of 1996-97 for example.  In that season the overwintering 
population in Mexico was at an all time high of 179 million butterflies
http://www.saber.net/~monarch/post.jpg  and the numbers of monarchs 
that survived the winter in Mexico to return to the USA was also at a record
high. This is how Dr. Taylor described the spring migration of 1997:

"The spring migration of 1997 was nothing short of spectacular. The numbers
of adults, eggs and larvae reported by observers was truly amazing"

With regard to the summer breeding and fall migratory populations of 1997
Chip wrote:

"I predicted the best fall migration in 20 years and reports from observers
this fall [1997] supported this prediction."

But in fact the size of the overwintering population measured in Mexico 
in Dec. 1997 turned out to be way below normal - only 32 million 
http://www.saber.net/~monarch/post.jpg and 
down a whopping 82% from the 179 million measured in Dec. 1996! 

Thus we see that a catastrophic decline occurred in the fall migratory
population despite the "nothing short of spectacular" numbers of monarchs
returning from Mexico in the spring of 1997.  This is why I don't agree with
what Dr.Taylor told us today:

"the deaths of tens of millions of monarchs 
at the two largest monarch overwintering sites in Mexico once 
again confirms the long held view that it is the overwintering
sites that hold the key to the continuation of the monarch
migration in eastern North America."

I disagree because the 80% population decline that occurred this
winter in Mexico is no different in magnitude than the 82% decline that 
occurred in the fall of 1997 before the butterflies even reached the 
overwintering sites in Mexico.  

Now last spring we saw how a record LOW number of returning 
overwintered migrants from Mexico can lead to an ABOVE normal
fall migratory population just six months later.  Dr. Taylor wrote
today:

"Last year [spring 2001] the number of returning females was at 
an all time low (4-5 million)."  

Yet we see the overwintering population measured in Mexico
in Dec. 2001 was about 35% above normal and 3-4 times as large
as the previous winter. http://www.saber.net/~monarch/post.jpg

In sum, in my opinion this evidence does not support Dr. Taylor's 
view "that it is the overwintering sites that hold the key to the 
continuation of the monarch migration in eastern North America."

Paul Cherubini
Placerville, Calif.

 
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