I can’t recall ever seeing a Monarch Butterfly near my home after late October. So I was very surprised when I saw a Monarch Butterfly migrating along the beach in Montauk, Long Island, New York on November 26, 2011, about one month later than ever before. Considerably south of here, in Cape May at the southern tip of New Jersey, a Monarch autumn migration monitoring program ends on October 31 (http://capemaymonarchs.blogspot.com/). No one in this region really expects them into November. Yet, here was this butterfly at month’s end. Why so late?
I had gone to Montauk to winterize my boat. But it didn’t seem like winter. I remember, back in what seems like the Pleistocene (1980s), that being around boats in late November included wool hats, hot thermoses, lined pants, thick socks, heavy gloves, and usually a bucket of water on deck to wash off the frost before untying the boat. The water to the marina hoses and bathrooms would be off for winter. I’d quit fishing for the year because my fingers would get painfully cold. But this year on November 26, I left my jacket in the car and pushed up my sleeves. At the helm I was too hot anyway, and opened the canvas. I wasn’t sure why I was winterizing the boat, because despite the calendar, the water was running, the fish were running—there were plenty of fish being caught—and there were tourists on the docks. And—there was that butterfly. In earlier times, frosts would most likely have killed any such lagging southbound flutterers well before this date.
As I wrote in The View From Lazy Point, for beauty and the awesome mystery of evolution on our coast, nothing exceeds the epic complexity of the migrations of these big-winged bugs. Theirs is no simple north-south. It’s a bizarre, multi-generational migration. Three generations go only north. One generation goes from Mexico to southern U.S. The next generation goes from southern to northern U. S. The third generation hatches in the northern U. S. and finally reaches Canada. Only the fourth generation goes south, but it goes all the way from Canada to mass-wintering sites in central Mexico. (On the west coast, some Monarchs winter in sites in California.) Northbound migrants live only about two months. Those making the southbound trip survive about nine months. This raises questions bigger than the butterflies themselves: how do they “know” what generation they’re from and what they are supposed to do? And if their hatching latitude somehow determines their directional tendencies, we still have the question of how one generation is programmed to live so much longer. Scientists first realized the extent of their southerly migration in 1975, when tagged butterflies were discovered in a small number of sites in the mountains of Mexico. Those few sites harbored millions of butterflies. These Monarchs passing our local dunes must travel up to 2,500 miles in about a month, to a place none of them has ever been, and that their parents and grandparents never saw. Migrating Monarchs experimentally moved hundreds of miles off course can re-orient using Earth’s magnetic field, change heading, entirely alter course—and go to the right place. They weigh one-fifth of one ounce. What they know is what they need to know. What they don’t know is that their Mexican destination is in danger. Logging is shrinking their winter sanctuaries. And the numbers of Monarchs are dwindling. In cold weather, without their sheltering forest, they can die. In one storm, 80 percent of the butterflies in one of their Mexican wintering sites died.
But will climate change alter their basic biology, or further challenge their survival, or actually help them survive the winters? The answer is fluttering in the wind.