El Nino has struck hard in many places this winter and the area of Mexico where Monarch butterflies overwinter has been devastated by the effects of winter storms. This is tragic news for the people who live in these regions, but it has been a real disaster for the Monarch.
Unprecedented rainfall from late January through the first week of February led to flooding and landslides that resulted in the loss of many lives and in the near destruction of the towns of Angangueo and Ocampo, the two municipalities that serve as base for tourists who visit the Monarch colonies at Sierra Chincua and El Rosario. The community of El Rosario was also hit with a major landslide that buried more than a dozen residents and destroyed much infrastructure in the region. The consequences of this disaster will be felt by the residents of this area for years to come. But it wasn't only people who were affected.
The Monarch colonies were strongly impacted by the unprecedented rainfall. The final estimate on the mortality suffered by the butterflies is not yet complete, but it is already clear that more than 50% of the overwintering population died as a result of the harsh winter conditions. It is expected that the number of Monarchs returning north this spring will be fewer than at any time since the wintering colonies became known to science in 1975. These numbers are so low that they are sure to have a long term effect on the butterfly population and the number of Monarchs that will be available to make the flight back to Mexico next winter is likely to be substantially less than in recent years.
I saw my first Monarch of the year in my garden earlier this week on March 22. In the winter of 2008-09, I had Monarchs overwintering in my garden. The weather was so mild that I had butterfly weed full of fat Monarch caterpillars on January 1 of that winter. The winter just past was quite different. We had our first hard freeze on December 4 and it remained cold from then through the end of February. I did not see a Monarch in my yard after December 4 until this week.
My butterfly weed is planted and waiting for any of the beauties that may need to deposit their eggs there, but I haven't seen another of the butterflies since my first sighting. I've had a few Swallowtails and Sulphurs and yesterday I had a Red Admiral, but no more Monarchs. Yet. It is very unusual to be near the end of March with only one Monarch sighting. Obviously, this does not bode well for the monarchy.