Burden of proof re: butterfly releases
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
Chincua El Rosario Total Fall Migration
colony colony Census*
1985-86 1.31 acres 5.08 acres 6.39 acres
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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