Paul Cherubini monarch at
Sun Mar 10 20:20:11 EST 2002

Bob wrote:

> The monarch's winter roosts are fragile as you well know. If
> the density of trees change the, the temp changes and so on...the
> monarch's freeze. 

Bob, no one has ever noticed a correlation between forest density
and monarch mortality during storms and freezes in Mexico.  

For example, look at what happened this year:

MONARCH           OYAMEL FIR       MONARCH           
COLONY                DENSITY             MORTALITY
                              TREES / ACRE      JAN. 2002 FREEZE    
Chincua                 251 trees/acre              30%
El Rosario             102 trees/acre               47%
Cerro Pelon            36 trees/acre          minimal mortality
Herrada                 290 trees/acre         minimal mortality

And look at what happened during the Jan. 1992 freeze:

MONARCH           OYAMEL FIR       MONARCH           
COLONY                DENSITY             MORTALITY
                              TREES / ACRE     JAN.1992 FREEZE    

Chincua                 251 trees/acre              25%
El Rosario             102 trees/acre               25%
Cerro Pelon            36 trees/acre               70%
Herrada                290 trees/acre                90%

I also have photographic evidence that substantiates the first
set of data above.

For example in the table above we can see the forest 
density at Chincua is very high, about 251 trees/ acre.
Here is a picture of the area of the Chincua forest that the 
monarchs were using when the Jan. 12, 2002 snowstorm freeze hit:
Very thick indeed! Now despite this high forest density, when 
I walked inside this thick forest at Chincua on Feb. 25, 2002 I saw
heavy butterfly mortality from the Jan 2002 freeze:

Also in the table we can see the forest density at El Rosario is
about 102 trees per acre - less than half as thick as at Chincua.
And here is a picture of the mortality I saw at El Rosario on
Feb. 23, 2002.
As you can see, the density of dead monarchs on the ground
at El Rosario appears similar to what I photographed at Chincua

Finally, the notion that forest thinning exposes the monarchs to
more rain, snow and freezing temperatures is misleading because 
it ignores the fact that monarchs avoid clustering in overly dense 
portions of the forest to begin with. Instead monarchs "like" to
cluster in areas of intermediate forest density and which are
located adjacent to natural or man made clearings in the forest:


Paul Cherubini
Placerville, Calif.


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