CHICAGO (AP) - Butterfly observers in Illinois are seeing a phenomenon this year that is playing out nationally: As the monarch starts its near-3,000-mile winter migration from Canada to Mexico, their observed numbers are extremely low.
Chicago Academy of Sciences chief curator Doug Taron tells The Chicago Tribune (http://trib.in/2bMjoQj ) the monarch is "the second or third most common species" of butterfly that observers record, but that this year, it's the "seventh."
Taron says this summer has been "pretty dismal" for butterflies in general in Illinois. Observers typically record 85 species a year, but current reports show 68 this summer.
Monarch Joint Venture co-chair Karen Oberhauser says the monarchs' difficult summer began March 9 in forested mountains near Mexico City, where tens of millions of them spend their winters. An intense storm lashed the area with rain, hail and snow, killing large numbers of the butterflies and inflicting heavy damage to their habitat.
Data from Monarch Larva Monitoring Project shows the number of butterfly larva this year rivaled the level seen in 2013. That year yielded "the lowest number of monarchs ever seen in Mexico," a Monarch Joint Venture report stated.
Since about 1996, the monarchs' presence in their Mexico habitat has been shrinking, from almost 45 acres to 9.9 acres recording in 2015, according to World Wildlife Foundation figures.
Oberhauser claims that wider use of herbicide-tolerant crops enables farmers to apply more herbicides, killing milkweed in farm fields.
Local and state efforts are underway to try to turn around the decline. Chicago Wilderness announced a priority species project that focuses on improving the health of 12 species that represent rare ecosystems. Monarchs are included. The Peggy Notebaert Nature Museum, where Taron works, is a partner in that effort.