Number of monarchs drop in Mexico

[Turtlehead]

Number of Monarch butterflies drop by 'ominous' 59 percent in Mexico reserve, experts report
Published March 13, 2013
Associated Press
MEXICO CITY – Scientists say the amount of Monarch butterflies wintering in Mexico dropped 59 percent this year, falling to the lowest level since comparable record-keeping began 20 years ago.
It was the third straight year of declines for the orange-and-black butterflies that migrate from the United States and Canada to spend the winter in mountaintop fir forests in central Mexico. Six of the last seven years have shown drops, and there are now only one-fifteenth as many butterflies as there were in 1997.
The millions of Monarchs cluster so densely on tree boughs that researchers don't count their individual numbers but rather measure the amount of forest they cover. This winter, they covered just 2.93 acres (1.19 hectares), down from 7.14 acres (2.89 hectares) last year.


Read more: http://www.foxnews.com/world/2013/03/13 ... z2NSlSjLby

[Paul Cherubini]

Just 9 months ago (June 2012) the monarch news was very encouraging:

http://www.learner.org/jnorth/monarch/s ... 62012.html

"What a Year! Spring migration 2012 has been a record-breaking season and it's going out with a bang. During the past few weeks, monarchs have appeared in unprecedented numbers, early, and in places where they're rarely seen."

Then during July & August the monarch summer breeding population in the upper Midwest went downhill fast due to an abundance of monarch egg and caterpillar parasites (e.g. tachinid flies) and predators. So monarch enthusiasts in the upper Midwest told me they had a hard time finding healthy mature caterpillars in July & August despite the abundance of monarch adults in May, June and July. On this forum they also reported the heavy predation. So the very low overwintering population in Mexico was anticipated way back in August.

Presumably the mid-summer abundance of parasites and predators in the upper Midwest resulted from the much warmer than normal temperatures last spring and early summer. But those temperatures were not wildly unusual when you look at the 1895-2012 history of April-July temperatures in the corn belt region of the upper Midwest: http://img560.imageshack.us/img560/5250/aprjuly.jpg

[giginy]

do they say what the main contributing factors are for this all time low?

[Mona Miller]

do they say what the main contributing factors are for this all time low?

Major contributing factors: drought in the midwest; GMOs in Canada, US, and now Mexico (use of roundup to kill weeds, kills milkweed, no milkweed, no monarchs), habitat loss due to development and farming.

[Paul Cherubini]

do they say what the main contributing factors are for this all time low?

Monarch enthusiasts in the upper Midwest and Great Lake States know what happened. The warm preceeding winter and warm spring and early summer weather resulted in a high population of monarch egg and young caterpillar predators. So in large milkweed fields like the ones pictured below, it was almost impossible to find any monarch caterpillars by August and September:
http://imageshack.us/a/img197/8742/midwestb.jpg
http://imageshack.us/a/img546/8279/midwestc.jpg
http://imageshack.us/a/img268/8296/midwesta.jpg
http://imageshack.us/a/img51/8015/milkweede.jpg
http://imageshack.us/a/img32/1851/milkweedi.jpg
http://imageshack.us/a/img543/5874/milkweedd.jpg
http://imageshack.us/a/img201/4814/midwestl.jpg