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Island Marble Butterfly


The Island Marble Butterfly is recognized as one of the most endangered butterflies in the world, with only about 200 known to be living in a single area on San Juan Island.


WE WANT YOU to help support suitable habitat on land you may have available. The Conservation District is working directly with landowners to establish and maintain habitat that is known to support Island Marble reproduction.


Since 2020, SJICD has worked with private landowners to establish protected habitat plots - fencing deer out of nearly 25,000 square feet of land containing host plants that the butterflies rely on for food, shelter, and laying fragile eggs. By 2025, we plan to add ten new plots in strategic locations along IMB flight paths on San Juan and Lopez Island. Interested in learning more or would like to get involved? Please reach out to the IMB team by emailing


Island Marble butterflies are being supported through the planting and protection of habitat areas in partnership with US Fish and Wildlife, Washington Department of Fish and Wildlife, National Parks Service, Bureau of Land Management, San Juan Preservation Trust, San Juan County Land Bank, San Juan Islands Conservation District, and many private landowners.

Habitat plots are planted with a brassica seed intended to flower bright yellow throughout spring and summer, attracting migrating butterflies across a broader range. The Brassica rapa (field mustard) is known to support the butterfly throughout their entire lifecycle. The plots range in size from 100 to 5,000 square feet and are located on both San Juan and Lopez islands. Deer fencing of the perimeter helps ensure host plants and butterfly eggs, larvae, and chrysalises do not fall victim to deer foraging or human intrusion.


Washington Conservation Corps crew celebrates the completion of a protected butterfly habitat.

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