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Island Marble Butterfly Field Season Ends

Kathleen Foley tends an island marble butterfly habitat expansion plot on Frazer Homestead Preserve

The rare island marble butterfly has completed its active field season. Flying adults that emerged this spring successfully mated, and the eggs and larvae produced have now transformed into tiny gray pupae that are overwintering in vegetation along the grasslands, dunes and saltwater lagoons at the south end of San Juan Island. A new year-long, miraculous life cycle has begun.

The Preservation Trust continued its vital role in the conservation efforts for this beautiful butterfly. Our “Suitable Habitat Patches” (SHPs) at Frazer Homestead and Sundstrom Farm Preserves produced abundant host plants (Brassica rapa, or field mustard) for the adult butterflies. Alas, despite rigorous monitoring, we did not observe marbles at the sites.

The absence of island marbles outside American Camp reinforced what we already knew. The butterfly is so greatly diminished that finding its way to our SHP “safe zones” was problematic. While disappointed, we know we are on the right track for supporting its expansion back across San Juan Island.

In another way, though, the season was a success for the Habitat Expansion Project. The patches at Frazer and Sundstrom not only provided viable host plants for the butterfly, but the knowledge that was gained in propagating native nectar plants to support the butterfly into early summer was invaluable as we move forward with a strong conservation effort. Next year, these “safe zones” will be back and better than ever.

“Each year we learn a little more about the plants the marble needs, and how well they can survive in these altered environments,” said SJPT Stewardship Manager Kathleen Foley, who is managing the project. “Until the butterflies make their home here, we will continue to care for these patches and keep the welcome mat laid out for them.”

Island marble—while still in peril—held on this season. The Preservation Trust, along with its partners, continues the fight for its ultimate survival here in the islands.

2018-09-26T05:24:55+00:00August 13th, 2018|