June 25, 2018
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Monarchs’ reign threatened? Sharp drop in Maine butterfly population worries scientists

By Beth Brogan, BDN Staff

GUILFORD, Maine — Robert Shaffer has seen only one monarch butterfly in the last two months on his 3-acre butterfly preserve at the Trebor Mansion Inn.

Even the town’s convenience story, where the bright orange and black wings usually litter the pavement after bouncing off car grills, is devoid of the migratory creatures this summer.

In fact, although Trebor Mansion typically hosts butterflies throughout the season, Shaffer has only seen five butterflies altogether since July.

“Something is very wrong,” Shaffer said.

Organizers of a seven-year butterfly survey of Maine agree, wondering whether the scarcity of the monarchs could be “the canary in the coal mine” — a sign that environmental problems along the monarchs’ long journey from Mexico to Maine each year are jeopardizing the species.

Monarchs spend the winter in the mountains of northwest Mexico and begin flying north in March. When they reach areas where milkweed grows, they reproduce in the tall weeds and then die. Their progeny continues the migration, stopping in the Midwest and then repeating the process three more times.

“By the time the butterflies get to Maine, they are the great-grandchildren or great-great-grandchildren of the first generation,” said Colby College biology professor Herb Wilson, one of several organizers of the Maine Butterfly Survey.

But “there’s a weak link in the chain somewhere,” Wilson said. It could be excessive logging in the Mexican hills, where the monarchs occupied a smaller area last winter than ever previously documented, according to Maine Department of Inland Fisheries and Wildlife biologist Phillip deMaynadier.

Or an increased use of herbicides in the midwestern United States could be a factor, because those chemicals also reduce weeds — including milkweed — where butterflies breed.

And climate change is likely a cause, deMaynadier said, creating more icy rain rather than snow in the Mexican highlands, which leads to butterfly die-off.

As part of the Maine Butterfly Survey, Wilson, deMaynadier and others are nearing completion of a seven-year effort to track the range of the 120 butterfly species in the state and their abundance.

Butterflies are important wildflower pollinators and are, especially in the caterpillar stages, a food source for larger species including dragonflies and birds, according to deMaynadier. They are also ecological indicators of “ecosystem stress” due to climate change, pollution and habitat loss.

So each year, more than 200 volunteers have headed out into fields to track the butterflies including monarchs, which deMaynadier says are “colorful, conspicuous, cooperative and charismatic,” and a perfect ambassador for butterflies in general.

Bob and Rose Marie Gobeil of Saco have conducted butterfly safaris on Swan Island, across the Kennebec River from Richmond, every two weeks all summer.

“At the moment, we have yet to see a monarch on Swan Island, which is very unusual,” Bob Gobeil said. “We might find one or two on our next visit, at the height of the migration within that area. Swan Island is loaded with milkweed plants, so it’s very unusual that there wouldn’t be at least a few monarchs on the island.”

The population of monarchs in Maine fluctuates from year to year, and Wilson said it’s possible that this year was a minor aberration. But it could prove to be “the canary in the coal mine — an indicator of what we hope will certainly not happen.”

“We’re certainly not crying wolf,” deMaynadier said. “We have several examples of butterfly species that are extinct in Maine … Our goal is really to prevent that from ever happening again in Maine.”

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