Macoun’s Arctic Butterfly on Isle Royale National Park

Documentation by Dr. Gard Otis proves that the Macoun's Arctic butterfly still has healthy populations on Isle Royale.

Photo by John Gregg

If you take a stroll in Michigan and catch sight of the Macoun’s Arctic butterfly, then you must be at Isle Royale National Park! According to Dr. Gard Otis of the School of Environmental Sciences , University of Guelph in Ontario, Canada, Isle Royale is the only place in Michigan where the Macoun’s Arctic butterfly is found. Prior to Dr. Otis’ visits to the park in 2012 and 2014, no surveys of this species had been conducted since the 1980s. In the absence of sightings, park staff had come to believe that the species had become rare on the island. His observations in 2012 and 2014 demonstrated that the population of Macoun’s Arctics on Isle Royale is actually healthy and not in any imminent danger of disappearing!

Dr. Otis shared some interesting facts: Adult Macoun’s Arctics, although common, are often overlooked by park visitors. Adults are almost perfectly camouflaged when at rest on the ground. When disturbed, their dull orange coloration is conspicuous as they take flight, but they quickly “disappear” upon landing. Individual butterflies take two years to mature from egg to adult. This extended development is unusual among butterflies. It probably evolved in an ancestral species that lived in cold arctic conditions where development within a single year was impossible. And here’s another fun fact: adults only occur in even-numbered years on Isle Royale and elsewhere in the eastern portions of its range. Try looking for them in June of 2020!