Monarch Butterfly Migration Update: May 23, 2001
Today's Report Includes:
When we left off last week, monarchs of the first generation had clearly emerged in force and were advancing northward. During the last week another 75 sightings have been reported, reflecting a surge in butterfly numbers. As today's migration map shows, the butterflies have now spread as far as 46 North.
Please Help: YOUR Monarch Sightings Are Important!
Even if early monarchs have already been reported from your state or province, we want to hear from YOU! The number of sightings we receive reflects how abundant monarchs are, so your observations continue to be important.
We'll continue to track the monarchs until they reach the end of the migration trail, sometime in mid-June.
This Week's Monarch Population Dynamics Meeting
Scientists and "citizen scientists" from the United States, Canada, Mexico and Australia gathered this week to address concerns about the apparent decline of the monarch population that migrates annually to Mexico from across eastern North America.
According to Drs. Karen Oberhauser and Orley Taylor who convened the meeting, "Recent reports on the degradation of the forest at the overwintering sites in Mexico, the possible impact of transgenic crops such as Bt corn on monarch populations, and the changes in agricultural practices that may affect the availability of milkweeds host plants, raise significant concerns about the potential impact of human activities on the dynamics of monarch populations."
The goal of the meeting was to identify gaps in knowledge about the factors that affect the size of the monarch population. Participants presented scientific papers and then addressed each stage of the monarch's annual cycle: The breeding season, fall migration, the overwintering season, and the spring migration. Groups summarized what is known about each stage of the cycle, and worked to identify priorities for research.
Of special interest to Journey North participants, the migration observations you are contributing are becoming very useful to scientists! Journey North migration data show where monarchs are located in time and space. Thus, the database can serve as an important indicator of the population's size each spring, and help to forecast the size of the next generation.
Says Dr. Lincoln Brower, "The database is so rich in terms of making it possible to address questions that were only speculative based on historical natural history information in the literature. For the first time, individual, qualitative records are being amassed into a quantitative picture."
Journey North program director Elizabeth Howard's presentation summarized clear and consistent patterns of remigration, based on an analysis of five years' data:
What's more, two scientists are using Journey North data to support a new theory about monarch migration. In
the presentation by Drs. David Gibo and Orley Taylor entitled "A General Theory to Explain the Movement of
Migrating Monarchs Across Latitudes," they explained:
Dr. Johannes Feddema, a geographer and meteorologist from the University of Kansas, has also incorporated Journey
North data into a computer model. This kind of model will ultimately be used to simulate monarch population dynamics,
and will serve as a critical indicator should populations fluctuate to dangerously low levels.
The Next Monarch Migration Update Will Be Posted on June 1, 2001