Hundreds Of Rare Oregon Butterflies Released To Save Threatened Species

Conservation specialists have released 1,304 Oregon silverspot larvae along the coastal range in an effort to protect a threatened butterfly species.

The larvae were raised at the Oregon Zoo before being transported to coastal release sites, where they will continue their development into adult butterflies during the summer.

Once common in coastal grasslands stretching from Northern California to British Columbia, the Oregon silverspot now exists in only a small number of isolated populations. Conservation efforts are focused on establishing new populations at Nestucca Bay and Saddle Mountain, where the early blue violet still grows in significant amounts.

The early blue violet serves as the primary food source for silverspot caterpillars as they grow. However, much of the species’ original habitat has been lost due to invasive plants and forest succession, leaving limited suitable environments along the coast.

Oregon Zoo conservation propagation specialist Julia Low noted that the butterfly requires very specific habitat conditions, and that much of its former range has disappeared, while efforts continue to support its survival.

Each year, field biologists collect a small number of female butterflies and bring them to the zoo to lay eggs. The eggs hatch into caterpillars, which are cared for through winter dormancy before growing rapidly in spring and being released into the wild.

Around 80 caterpillars remain at the zoo this year to complete their transformation and reproduce for future releases. The Oregon Zoo became the first facility to successfully breed the species in 2019.

Since the program began in 2000, more than 36,000 Oregon silverspot butterflies have been released through coordinated efforts with conservation partners.