PORTLAND (AP) — Conservationists have successfully bred the extremely rare Oregon silverspot butterfly in captivity, a potential breakthrough for saving a species that once was found in coastal regions from California to British Columbia but is now reduced to five isolated populations, the Oregon Zoo said.

The captive breeding resulted in 269 silverspot caterpillars that will be released into the wild once they transform into butterflies.

“This is a really exciting breakthrough,” Tia Perry, a keeper in the butterfly conservation lab, said in a statement Tuesday. “Not only does it mean we can release more silverspots in Oregon but it’s something that can benefit the imperiled population in California as well.”

Perry said wild silverspots lay their eggs in the Oregon Zoo lab each year, but this is the first time a female butterfly bred in captivity. At the request of the U.S. Fish and Wildlife Service, the zoo’s butterfly conservation lab held back 22 pupae from this year’s butterfly release and one of the resulting female butterflies mated in captivity with a wild male.

The lab had hoped that more females might breed in captivity, but with such a fragile species “every egg counts,” Perry said.