Endangered Key Deer Face Threat Straight out of a Horror Movie

The invasive screwworm bores into the animals’ bodies and eats them alive, but science has a solution.
Two of the tiny Key deer that inhabit the Florida Keys. (Photo: 'The Denver Post' via Getty Images)
Oct 6, 2016· 2 MIN READ
Richard Conniff is the author of House of Lost Worlds: Dinosaurs, Dynasties, and the Story of Life on Earth and other books.

Let’s face it: Key deer, a slightly smaller, stockier subspecies of the common white-tailed deer, have plenty of problems. Only about 800 of them survive, confined to a few small islands in the Florida Keys. You could whip through their entire habitat in about 10 minutes on Route 1, and plenty of motorists do, incidentally killing about 150 of the deer every year. They’re on the endangered species list.

Sound bad? Early this week, it got much worse.

Staff at the National Key Deer Refuge found deer infested with maggots of the New World screwworm fly, an invasive species that hasn’t been seen in this country in half a century. The flies have a nasty habit of laying their eggs on open wounds, and when they hatch, the maggots feed by digging corkscrew holes into the flesh of the host animal.

“They’re in as gory of a condition as you can imagine,” Dan Clark, the refuge manager, told a reporter. He wasn’t exaggerating: One photo showed a deer waiting stoically as the writhing maggots seemed to be peeling the skin off the back of its head. U.S. Fish and Wildlife staff charged with protecting the deer began euthanizing the victims instead, by firing a spring-loaded bolt into their skulls. Then they collected the maggots to prevent them from spreading. So far about 40 of the infested deer have died.

(Photo: Steve Waters/'Sun Sentinel'/MCT via Getty Images)

Other government officials weren’t fretting so much about the endangered deer. They worried instead about cattle, another invasive species. Mention of screwworm flies “sends shivers down every rancher’s spine,” said Adam H. Putnam, Florida’s commissioner of agriculture. He declared a state of emergency, noting that Florida’s livestock industry “generates $2.78 billion in annual economic impact and supports more than 41,000 jobs.” The state has established an “animal health check point” to spot screwworm-infested pets in vehicles leaving the quarantined zone.

Despite the scary headlines, livestock ranchers (and pet owners) probably don’t have much to worry about. The U.S. government succeeded in eradicating the screwworm fly from this country in the mid-20th century, though it persisted in South America and on a few Caribbean islands. (How the screwworm returned remains unknown.) It did so then—and will do so again—with the help of the sort of taxpayer-funded basic research that shortsighted politicians love to ridicule. Back then, U.S. Sen. William Proxmire got wind of a $250,000 federal research grant to a Texas entomologist named Edward F. Knipling. Proxmire singled out the project for one of his Golden Fleece Awards because studying “the sex life of parasitic screwworm flies” just seemed like a waste of taxpayer dollars.

Knipling was developing what some scientists have praised as “the single most original thought in the 20th century.” It involved releasing large quantities of artificially sterilized male screwworm flies. Female flies of the species mate only once, and because mating with sterilized males produced no eggs, the wild population quickly dwindled, leading to eradication in 1966.

The continuing benefit to cattle ranchers just from the screwworm program is worth an estimated $1 billion year in and year out, not a bad return on a small taxpayer investment in basic science. Public health agencies have used the “sterile insect technique” against a host of other human and animal pests, and they have announced plans to use it again in the Florida Keys.

So where does that leave the Key deer? I’d like to say that all will be well once the screwworm fly invasion ends. But there is plenty of bad news to spread around: Rising sea levels mean that what’s left of Key deer habitat—low-lying hardwood hammocks, mangroves, and freshwater wetlands—could all vanish in this century. When that happens, there will be no place left for Key deer to call home.