Scientists confirm mixing between east and west populations of Monarchs

Paul Cherubini monarch at
Tue Feb 24 00:15:02 EST 2009

For years the Monarch Scientific Community has claimed:
"There are two geographically distinct Monarch populations in
North America. The eastern population overwinters in Mexico
and breeds east of the Rocky Mountains. The western
population overwinters along the California coast and breeds
in areas west of the Rockies."  And they published maps like
leading us to believe monarchs breed only "east of"
and "west of" the Rocky Mountains:and don't mix during

We now know those claims are innaccurate.  See this article:


Six rebel monarch butterflies who haven't done their
homework seem to have disproven a long-held theory
that monarchs east of the Rocky Mountains in Canada
and the U.S. migrate to Mexico for the winter, while
their western cousins hang out in California during
the cold months.

"This totally blows out of the water (the theory) that there
is some sort of hard dividing line between the east and
west populations," said Chris Kline, a scientist and former
teacher who heads the Southwest Monarch Study.

Three monarchs tagged in southern Arizona (west of the
Rocky Mountains and just north of the Mexican border)
were recovered in California, but another three tagged
in Arizona were found in the overwintering colonies in Mexico.

"Monarchs in Arizona obviously haven't read the textbook
- they're going both directions," said Kline, who was
education director at the Boyce Thompson Arboretum in
Arizona before moving recently to Columbus, Ohio, where
he is education director at Grange Insurance Audubon Center.

"Obviously they're not playing by the same ground rules as
all the other ones are."

Kline has team members in Mexico searching for his distinctive
light blue tags - tiny stickers placed on a particular spot on
a butterfly's hindwing that are considered not to harm the
insect. Other tagging programs, such as Monarch Watch's,
use white tags.

"The old theory was that the Continental Divide was the
magical dividing line, which means I have had three that
have flown the wrong way," he said.

A more recent theory is that the dividing line runs from
Boise, Idaho, to Yuma, Ariz., which means the other
three have flown the wrong way.

Kline has had monarchs recovered in Mexico and California
in recent years, but he said the results weren't taken seriously
because the butterflies were farm-raised and their navigational
systems may have been mixed up.

"Now we've got two wild butterflies that have done the exact
same thing as what those farm-raised ones released in Phoenix
did, which I think adds more credence to the issue," he said.

One wild monarch was tagged in Canelo, Ariz., and recovered
in the El Rosario monarch reserve in Mexico.

The other was tagged just 12 miles southwest of Canelo in Bog
Hole, Ariz.,but recovered in Ellwood Main, one of several
overwintering sites near Santa Barbara, Calif.

Paul Cherubini
El Dorado, Calif.


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