Levin: Ghost Butterflies

Oct 30, 2017

Recently, while visiting the rocky shores of Rhode Island and relaxing at George’s Beach in the unseasonable warmth of a protracted Indian summer, I watched a steady stream of monarch butterflies rise above pine and flaxen tangles and pass by our beach chairs.

All afternoon, as many as seven at a time became airborne and headed south by southwest on a course that would take them over Block Island to the twin forks of Long Island... and far beyond.

Then just the other day in Pomfret I noticed a monarch resting in a patch of goldenrod. The blooms had faded weeks ago, but the monarch’s distinctive glow was undiminished - four-inches of Halloween color on the cusp of Halloween.

Some of the Rhode Island butterflies could have come from Vermont - like the one banded in Essex Junction on August 18 in 2000 that arrived fifty-seven days later on the South Fork of Long Island. It had flown two hundred and fifty miles with an average southward progression of approximately four-and-a-half miles a day. At a similar rate, it would take the Pomfret monarch until the summer of 2019 to complete its journey to the wintering grounds in the oyamel fir forests high above Mexico City, some twenty-five hundred miles away.

Of course, migrant monarchs only live eight months, so butterflies that overwinter in Mexico breed and die on the Gulf Coast, usually that same winter. Several generations later, monarchs appear in Vermont just before summer, where after another two generations, the southbound migratory cycle beings again.

In natural cycles, timing is everything. Birds feast before they migrate and not so much en route, often arriving on the wintering grounds dangerously depleted. Monarchs, however, migrate by day and roost by night. They feed the whole way south and reach Mexico heavier than they were when they left. Then, once they arrive, they fast.

Monarch caterpillars feed only on milkweed leaves, while adults visit a variety of flowers, including various species of goldenrods, Joe-Pye weed, red clover, and New England aster. But with climate change reshuffling the ecological deck, our Pomfret butterfly, lighter than an oak leaf, may find food scarce on the long road ahead.

In 1996, a billion monarch butterflies over-wintered in Mexico. By 2014, the population had collapsed to thirty-three million.

By delaying the start of its migration until so late in the season, I hope our Pomfret butterfly doesn’t turn into a Halloween ghost.