Journal: How do you explain the monarch in Massachusetts?

May 3, 2007

Dear Clare,
I just saw your monarch sighting appear on the migration map. How fascinating--and unusual!

Of course nobody can answer your question about where the monarch originated definitively. It is certainly possible to see a monarch this early in MA. I know we have had early records before. In fact, a 12-year old girl saw a monarch on Cape Cod on April 7, 1997 and even sent a picture of its wings. >>

Cold temperatures are the obvious reason you wouldn't expect a monarch so early. An additional reason, however, is that the monarch population is so small in April. Adult monarch butterflies are relatively rare right now. This is because the overwintering generation from Mexico has died and we are waiting for their offspring to develop.

One possible explanation for your sighting is that your monarch did not come from Mexico. Some monarchs do overwinter along the Atlantic Coast as long as frost does not kill them. During the winter of 2005/2006, two tagged butterflies stayed in Virginia all winter, providing direct evidence of this. Thus, it's possible that the monarch you saw came from the East Coast. (You may recall the HUGE migration last fall. Perhaps numbers along the coast were higher this winter.) Our migration map shows where the monarchs overwintered this year. Watch the animated map; it seems to show monarchs moving inland from the Carolina coasts.

The fact that you are on the ocean is of interest. Monarchs avoid crossing open water, so coastlines funnel the butterflies as they travel. Thus, even though there are very few monarchs now, those that are in your region might be blown to the coast and then travel along its edge.

Another possibility is that the monarch was released as part of a wedding or other celebration (or even released from a lab). Many companies now sell captive-raised monarchs for such celebrations, although it would be early to do so in April.

Finally, the fact that people are watching and reporting their observations means the "unusual" goes on record. Perhaps it's more common than we realize for a small number of monarchs to be seen each spring in MA, but they previously went unrecorded.

These are a few of my thoughts. Thank you so much for reporting what you saw. It's exciting to hear from you!

Elizabeth Howard
Journey North

Here is the letter I wrote to Clare Walker Leslie in response to her question. I hope the ideas in my letter will help you review the letters students in your class write.