It's been a tough year for monarch butterflies, and their observers have fingers crossed that this winter is kinder to them than last.
Over the following weeks, across the eastern half of the United States, citizen scientists, professors and students from second grade to college will engage in an activity that the second-graders may be better at than the professors — attaching tiny tags to the wings of monarch butterflies. (According to Monarch Watch, that just might be easier for people with little fingers.)
As autumn advances over the East, the butterflies can be observed making their epic migration back south to their ancestral wintering grounds in the tropical forests in the mountains just outside of Mexico City. Aside from the dramatic spectacle of their migration, the fortunes of this insect have been linked to the health of our ecosystems, the viability of rural economies and the crafting of international environmental policy agreements. Tagging them is one way to keep track of their fortunes.
It has been a turbulent year for the monarchs. Chip Taylor, founder of Monarch Watch, says the population that first left the key preserve in Mexico in early spring was smaller than usual, covering an area of only 4.61 hectares (11.4 acres), compared to the 6 hectares (14.8 acres) blanketed in previous years or the 9 hectares that used to be considered average. (Expect about 25 million butterflies per acre.)
On their way north, they arrived in Texas in April, a bit delayed, but in good spirit as evidenced by the "large number of larvae on milkweeds in pastures south of Dallas." But after that, they seem to have run into trouble, Taylor writes in the Monarch Watch Newsletter.
"The vast majority of reports" indicate the monarch population over early summer generations "to be much lower than usual."
Taylor says in his home state of Kansas, "during good years, the movement of first-generation monarchs through this area can be quite conspicuous with many of the passing monarchs stopping to lay eggs on the blooming milkweeds." But this year there was "no obvious flow" through the area and few eggs or larvae found on milkweeds in early May and June.
Taylor says cold weather and storms through late spring and early summer produced conditions that might have "reduced egg laying and increased mortality of adults," limiting monarch dispersal into their northern breeding ranges in New England and Canada.
He pointed out, however, that a bad year for butterflies might be a worse year for their enemies, starving out the predators and parasites that feed on larvae, leaving the field clear for the summer's final generation of larvae to mature relatively unmolested into migrating butterflies. If that happens, he says the population could rebound.
Nevertheless, based on what he has seen so far, Taylor fears the overwintering population will be smaller even than 2007, which was the third smallest in recent memory at the Monarch Biosphere Reserve.
A chart on the Monarch Watch Web site forecasts peak migrations for respective geographic regions. "Tagging and monitoring should begin in late August in all regions, with a concentrated effort made in September and early October," it reads.
(The site also offers a phenological hint, "When the wild asters, especially A. novae-angliae, goldenrod and Joe Pye weed are in bloom, the monarchs are migrating.")
Karen Oberhauser, professor of conservation biology at University of Minnesota and originator of the North American Monarch Conservation Plan, says the monarch's arrival in Mexico is eagerly awaited. "They attract tourists to the countryside, providing an economic boost to those rural communities."
Equally important, the butterflies also figure prominently in the cultural celebration known as the "Day of the Dead," or Dia de los Muertos, on Nov. 2, where, since Mayan times, the butterflies have come to "symbolize rebirth and the return of the ancestors."