Why an at-risk butterfly hunkers down at Pennsylvania’s biggest bombing range

The eastern regal fritillary butterfly once floated across meadows from North Carolina to Maine. Now the range of the vividly patterned insect is reduced to a single foothold inside the busiest National Guard training center in the country: Pennsylvania’s Fort Indiantown Gap.

The military base spans 17,000 acres in Lebanon and Dauphin Counties. It can host well over 100,000 personnel in a given year for small arms, air-to-ground bomb training, and more. And in the midst of all the rumbling and explosions (it gets loud), the last of the eastern fritillaries have made their home — not in spite of the bombings but because of them.

The violets, bunch grass, and nectar plants required by the insect have long been propagated, or at least encouraged, by ordnance and machines that churn the soil and limit the tree cover.

In the 1990s, a conservation-focused nonprofit brought a lawsuit over military plans to turn the butterfly’s habitat at Fort Indiantown Gap into a tank range. The case almost halted all training at the base, but ended with a settlement that saw hundreds of acres set aside.

But because the insect’s range remains so miniscule, the U.S. Fish and Wildlife Service this summer recommended it be placed on the endangered species list for the first time. A “threatened” label has been recommended for the western regal fritillary subspecies found from Montana to Oklahoma.

“The decline of the regal fritillary, along with the loss of other pollinators are indicators that something is ecologically out of balance,” said Pam Shellenberger, a biologist with the U.S. Fish and Wildlife Service’s Pennsylvania field office in State College.

Reintroduction efforts are underway in Pennsylvania but slow going. An abandoned surface mine owned by the Game Commission has shown promise. It’s located in an undisclosed county that used to have fritillary butterflies, and has an ecology that suits them. But it’s not clear yet if it’s enough to establish another tenacious population.

“The butterflies they are reintroducing there are showing to be a bit smaller than the ones at Fort Indiantown Gap, and they’re trying to figure out: Is that because they’re lab-reared? Is it because they just don’t have the violets or enough food sources to eat before they pupate?” Shellenberger explained. Conservationists are discussing cultivating violets, the butterfly’s favorite host, to help them. The trial and error is ongoing. The butterfly is finicky.

The species’ arc is familiar: Logging opened up grasslands across the Northeast. Over time, things like development consumed those plains or the trees returned. Neither change works well for the fritillaries, which prefer the kinds of sparse, uncluttered environments often left behind by natural forces like high winds, downed trees, and fires that eliminate biological competition for plants like violets.

At Fort Indiantown Gap, man-made explosions and controlled burns replicate nature’s stanching power and have allowed a fritillary population now numbered at around 1,000 to carry on. The work is quite involved, organizers say.

“Occasionally trees will pop up in there and we’ll remove them by hand. If it’s a big enough job we have some devices we can go in with and sort of eat away at the forest that’s growing up,” explained Mark Swartz, an invertebrate wildlife program manager at Fort Indiantown Gap.

Swartz said no one is exactly sure how or when the butterfly was first discovered at the base. In one version, a reservist recognizes the insect, already in decline, and rings the higher-ups. In another, a team of biologists doing a construction survey makes the discovery.

Either way, Swartz says, “it became a whole thing,” and 20 years later a conservation effort continues. Off base, a broader rescue effort is mounting in the form of a fritillary butterfly rearing and reintroduction program that’s seeing varying degrees of success.

“We’ve tried it a few places and when the habitat’s not right, you know right away,” Swartz said of the program, which counts Hershey’s ZooAmerica and several state agencies as partners.

Swartz has a pet theory that old coal mines offer favorable conditions for the plants fritillaries love, an idea he’d like to test out in another legacy coal state. “I’ve been wanting to look in West Virginia for a while,” he said.

New sites are always being recommended and Swartz said a small but mighty team is moving as fast as it can to vet them: “There are other places out there we definitely need to explore.”

The butterfly’s proposed endangered species listing is open for public comment through Oct. 7, 2024, online or by mail. The comments will be considered by policymakers.

Butterfly tours at Fort Indiantown Gap resume next summer.

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