Bats are just one subset of a broad market of taxidermied oddities that decorate hipster bars and are celebrated at curiosities expos in cities across the nation. But federal officials say they are increasingly concerned about the deceased bats because they seem to be growing in popularity, especially around Halloween.

The U.S. Fish and Wildlife Service, whose inspectors screen imports at the world’s largest international mail facility at John F. Kennedy International Airport in New York, says it has been seizing illegal shipments of dead bats once or twice a month since a bat trend appeared to take flight in 2015. That figure doubles in the late summer and fall months leading up to Halloween, said Naimah Aziz, a Fish and Wildlife supervisory inspector at JFK.

“I think the oddity trade is larger than we’ve realized,” Aziz said. “The only numbers that are reflected in our information system, that we know about, are the ones that are interdicted. That’s just a drop in the bucket . . . probably 3 percent of what’s actually coming into the United States.”

The bats being sent are various species, and they are not much larger than cellphones, which means boxes of them are lightweight, she said. They’re usually sent from Indonesia via regular mail, which is a growing method for smuggling some living critters, particularly sought-after sorts of scorpions and centipedes that can tough out a trip in a box.

The problem with bats is not usually that they’re endangered, she said. Aside from flying foxes, most species are not protected under international wildlife treaties or U.S. laws. But interdicted shipments typically are mislabeled and lack import-export permits, Aziz said. Discovering a box of bats in a mail bag, then, typically sets inspectors off on a quest to identify the species and, if it isn’t protected, track down the importer to get the paperwork sorted.

“We have one shipment of, like, 100 bats sitting on our referral table,” Aziz said, and inspectors are “waiting for a gentleman to obtain a license and declare the species.”

Painted bats, found across several Asian countries, are commonly used in taxidermy. (U.S. Fish and Wildlife Service )

There’s also another problem: the threat of fatal illness. All bat shipments are also referred to the Centers for Disease Control and Prevention, which requires an additional import permit for bats. The CDC says it regulates incoming bats because they are potential reservoirs for infectious diseases including rabies and Ebola. It requires that deceased bats are “properly processed” to render them safe, either with high heat, formaldehyde or another approved method.

Viruses such as rabies and Ebola “can’t survive for very long outside of the host, but can survive longer in a dead animal,” Brian Amman, an ecologist with the CDC’s viral special pathogens branch, said in an email. “While the likelihood is low that something like Ebola would be transmitted via an imported bat carcass, even a small chance with a potentially deadly disease is too much.”

How do the dead bats get dead? That’s unclear, Aziz said; cause of death isn’t required information even for legally imported bats — about 9,000 of which come into the United States each year, according to a Newsweek investigation that cited federal figures.

Many online sellers tout their taxidermied bats as “ethically and sustainably sourced,” and some say they’re trapped in nets by farmers whose crops bats damage. Human-bat conflict over crops occurs in many countries, and fruit bats are widely killed for that reason in Indonesia, according to the World Wildlife Fund. But the organization says the animals in fact play an important ecological role by pollinating and dispersing plants.

“The way they are preserved, it boggles my mind how they’re captured. They’re not decomposed whatsoever. They’re pretty much caught and probably treated,” Aziz said of the shipments found at JFK, whose numbers, she added, alarm her. “The amount that I see, it’s got to be impactful to the species.”