Sunday, April 24, 2011


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Dear Robert:

This paper has been written before but not by this grouping. The 2009-2010 results are new but the basic story is the same.

I have visited the major Monarch sites during the Boreal winter (N of 22 degrees) in Mexico and California (often forgotten). The sites in Mexico were visited in the 1960's and at various times up to around 10 years ago. Some years depending on the temperature the Mexican sites were a wonder to see. But in the 1980's there was bad weather and a great deal of tree cutting on the so-called protected sites. Dead Monarchs were piled up like dead leaves on the Boreal Autumn.

Migration routes are labile in evolutionary time. There are alternatives now visited by North American originating Monarchs in Mexico. The Californa sites are protected. Brower and Taylor should know that the "entire portion of eastern North American Monarchs" DO NOT use that site in Mexico. Have they never been in the state of Florida in the Boreal Autumn?

Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk?
RAMI´REZ6 1Department of Biology, Sweet Briar College, Sweet Briar, VA, USA, 2Department of Ecology &
Evolutionary Biology, University of Kansas, Lawrence, KA, USA, 3Department of Biology, Hamilton College, Clinton, NY,
USA, 4Science Systems and Applications, Inc., Biospheric Sciences Branch, NASA Goddard Space Flight Center, Greenbelt,
MD, USA, 5Posgrado en Ciencias Biologicas, Universidad Nacional Autonoma de Mexico, Coyoacan, Mexico D.F., Mexico and 6Centro de Investigaciones en Geografia Ambiental, Universidad Nacional Autonoma de Mexico, Antigua Carretera a Patzcuaro, Morelia, Michoacan, Mexico

1. During the 2009–2010 overwintering season and following a 15-year downward trend, the total area in Mexico occupied by the eastern North American population of overwintering monarch butterflies reached an all-time low. Despite an increase, it remained low in 2010–2011.

2. Although the data set is small, the decline in abundance is statistically significant
using both linear and exponential regression models.

3. Three factors appear to have contributed to reduce monarch abundance: degradation of the forest in the overwintering areas; the loss of breeding habitat in the United States due to the expansion ofGM herbicide-resistant crops, with consequent loss of milkweed host plants, as well as continued land development; and severe weather.

4. This decline calls into question the long-term survival of the monarchs’ migratory

1. Durante la temporada invernal 2009–2010, y siguiendo una tendencia a la baja de 15 an˜ os, la superficie total ocupada por mariposas monarca en Me´xico, provenientes del este Ame´rica del Norte, llego´ a su punto ma´ s bajo. A pesar de su incremento, dicha superficie siguio´ siendo baja en 2010–2011.

2. Aunque que el conjunto de datos disponibles es au´n pequen˜ o, esta disminucio´n de la abundancia de mariposas es estadı´sticamente significativa, tanto si se usan modelos de regresio´n lineales como exponenciales.

3. Hay tres factores que parecen haber contribuido con esta tendencia de reduccio ´n del nu´mero de mariposas: la degradacio´n de bosque en las a´ reas de invernacio´n en Me´xico; la pe´rdida de ha´ bitat de reproduccio´n en los Estados Unidos, debido a la expansio´n de cultivos gene´ticamente modificados resistentes a herbicidas, con la
consiguiente pe´rdida de las plantas hospederas de algodoncillo, y por continuos cambios en el uso del suelo no favorables para ellas; y, las recientes condiciones clima ´ ticas severas.

4. Esta disminucio´n hace que nos cuestionemos sobre la posibilidad de supervivencia a largo plazo del feno´meno migratorio de las mariposas monarca. Key words. Conservation, endangered biological phenomenon, habitat, Lepidoptera, migration, monitoring.

Robert Morton, M.Ed., Ed.S. writes about the natural world. Questions? Comments? Stories you'd like to publish here at no charge? Contact him at the secure Bpath Mail Form.