Burden of proof re: butterfly releases

Paul Cherubini cherubini at mindspring.com
Fri Oct 13 08:23:17 EDT 2000

Michael Gochfeld wrote:
> The burden of proof falls on those who believe there is NO danger or
> environmental risk from the butterfly releases.  Once they have "proven"
> that there is no danger through repeated, long term monitoring of all
> potential impacts, then skeptics might be convinced.

Painted Ladies have been raised and released by commercial breeders
by the hundreds of thousands per year since 1969. 
Monarchs since 1993.

Below is population monitoring data on monarchs since 1985. 
This data obviously includes all impacts - natural as well as man caused.
Size of Over-Wintering Monarch Population 
at Mexico's two largest colonies                      Cape May
                                                                         New Jersey       
                   Chincua     El  Rosario    Total      Fall Migration    
                    colony          colony                     Census*

1985-86    1.31 acres    5.08 acres    6.39 acres  
1992-93                                                                   92
1993-94    5.51 acres    8.82 acres  14.33 acres    433
1994-95    8.49 acres    8.84 acres  17.33 acres    941
1995-96  10.27 acres  10.74 acres  21.01 acres    244
1996-97  17.51 acres  18.79 acres  36.30 acres    397
1997-98    1.81 acres    5.23 acres    7.04 acres  1174
1998-99    4.84 acres    4.94 acres    9.78 acres    297
1999-00    2.27 acres    9.33 acres  11.60 acres  2031

*total of 8 weeks worth of cumulative averages of monarchs 
observed per hour at the end of each week in Sept. and Oct.
over the last 8 years.

The reason Cape May counts are poorly correlated with
Mexican counts is that it appears most Atlantic coast monarchs 
do not go to Mexico for the winter (some end up in Florida, the
Bahamas, etc). Only 1 in 1000 monarchs tagged at Cape May 
is recovered in Mexico vs. 1 in 70 monarchs tagged west of
the Mississippi Valley (e.g. in Kansas, Minnesota, etc). 
Interestingly, 1 in 216 released in western Colorado was 
recovered in Mexico - these butterflies had to fly across the 
Rockies and continental divide to get to Mexico and evidently
did so with ease.

Paul Cherubini, Placerville, Calif.

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