Reader Joe Dickinson sent a photograph of one of the places where Monarch butterflies (Danaus plexippus) congregate for overwintering (larval and pupal stages cannot survive the cold of the northern U.S.). There are two main areas where they do this: northeast Mexico and southern California/Baja California; for a good overview of the process, see this website from the U.S. Forest Service. Here are the two main migration routes south:
Joe’s notes:
Here are some shots from my annual visit to my favorite monarch “butterfly trees” in Santa Cruz (Lighthouse Field rather than the more famous Natural Bridges). To my eye, the population looks more robust than over the last couple of years. Dare one hope that that is a trend?
Here’s a video (not Joe’s) of the butterflies at Lighthouse Field:
That should be Michoacan, my home state!
One of our natural wonders, and everyone hopes it hangs on.
To think that I had lived in California for many years, in San Diego, and never went to see this marvel. Truth is, I did not know of it.
Numbers were up some in Connecticut last year for the first time in years. I keep hoping for a full come-back.
Nice butterfly report. As I mentioned last year, the milkweed along my walking route here in NY was badly damaged by a black mold or mildew. Only a few Monarchs were seen nearby. Very worrisome.
Inspired by this group of photographs i thought i could add to the post especially when you see the migratory paths monarchs take.
So from a book Life on the Edge by J Al-Khalili and J McFadden in brief, here goes.
A team of researches, Steven Reppert et al from The Uni of Massachusetts investigating magnetoreception, the ability to navigate by the earths magnetic field, replaced a defective light sensitive cryptochrome gene in a mutant fruit fly Drosophila which had no circadian sense, with a healthy gene from a monarch butterfly. This restored or allowed entrainment to correct the circadian rhythm (body clock) by light in the fly.
Following this, further experiments training the fly’s ability to sense magnetism in an arm of a maze for food they found flies with a defective cryptochrome gene flew randomly down any of the two path options in the maze, in short, they lacked the ability to sense magnetism.
Reppert’s team then replaced the defective cryptochrome gene in mutant flies with a healthy monarch gene which showed that indeed it corrected this fault as well, to sense the magnetized path and hence to the food.
So from these experiments the team concluded, the monarch butterfly possess a light dependent inclination compass.
Light, magnetism and a clock.
Tricky but not magic.