Armadillos are expanding further into the U.S.—and why is still a mystery
The armored mammals, native to the south and central U.S., have made it as far north as Virginia.
Roanoke, VirginiaWhen Nancy Moncrief began her job as curator of mammalogy for the Virginia Museum of Natural History in Martinsville in 1989, she figured the number of species on her watch wouldn’t change over the course of her career. And for two decades, her assumption seemed correct.
That all changed in May 2019, when she received an email from Mike Fies, a wildlife biologist at the Virginia Department of Wildlife Resources.
“Another Armadillo—Dead This Time,” read the subject line. Fies’s colleagues had found evidence of an armadillo two months before, but they had been unable to trap the animal for verification.
Moncrief, who studied at Louisiana State University, knew all about nine-banded armadillos, which are native to Central and South America, as well as parts of the U.S., including Texas. Her exact reply to Fies: “What the [expletive] are they doing in Russell County??”
There isn’t a clear answer. But what is certain is that the mammals, which each weigh about 12 pounds, have been moving steadily northeast over the past century, crossing the Rio Grande River in the 1850s and the Mississippi River during the Great Depression. In the 1990s, they arrived in Tennessee, then North Carolina, and now Virginia.
“It was a complete surprise,” says Moncrief, who published her findings on Virginia’s first confirmed armadillo in 2021 in the journal Southeastern Naturalist. “It’s just this wave of northward expansion.”
As of May 2022, Moncrief has collected several additional reports of armadillos in Virginia, although she can’t say for sure how numerous or widespread the species—most closely related to sloths and anteaters—are in the state. Officials in the neighboring states of Maryland and West Virginia haven’t reported sightings.
Yet several studies suggest that armadillos, which prefer hot weather, could one day thrive as far north as New Jersey and Pennsylvania, aided in part by warmer winters. Temperatures in the northeastern U.S. rose by two degrees Fahrenheit between 1895 and 2011, and could increase by up to 10 degrees Fahrenheit by 2080.
“People have always made these predictions that they’re not going to move past this point, and they’ve always just kept going,” says Colleen McDonough, an ecologist and armadillo expert at Georgia’s Valdosta State University.
“With warmer temperatures being found further north, armadillos could potentially be found in areas that were totally unexpected 20 years ago.”
James Taulman, a retired ecologist from Park University in Missouri, first began studying armadillos’ widening range in the 1990s. (See five reasons why armadillos are awesome.)
It’s still not clear whether the spread of this unusual-looking animal is part of its natural expansion, warming temperatures due to climate change, or both, he says.
But there’s no question these burrowing insect-eaters have no trouble adjusting to new habitats.
“It doesn’t take many armadillos to start a population—just a female and her male offspring,” Taulman says.
“If the area is suitable for them”—moist, insect-rich soil and mild winters—“they can get going.”
There are limitations to the animal’s spread, says McDonough: For instance, the species can’t disperse much farther west from Texas because the land is too dry to support the sheer number of insects needed for its survival.
She also suspects the armadillos’ colonization into the northeastern U.S. will be limited by cold temperatures and other unknown factors.
In Virginia, the wrinkled bedrock, dense hardwoods, and numerous creeks and streams of the Appalachians seem a far cry from the arid, open-range environment that most people picture as armadillo habitat.
In fact, Moncrief says, it’s perfect: The animals prefer to travel along shaded rivers and streams, where abundant food, shelter, and moisture create what she calls an armadillo superhighway.
On a recent spring morning just outside Abingdon, I eased my car to the shoulder of a serpentine country lane to take a closer look at a series of shallow earthen holes near a small creek—exactly the signs Moncrief and Fies had told me to look for in my quest to spot an armadillo.
A sudden rustle of leaves made me whip my head around; at 10 a.m., I knew the odds were low that I’d see the nocturnal creature. Indeed, the source of the sound was a common gray squirrel. Unless you have an armadillo in your garden, it’s generally tough to see the shy, house cat-size animals, which camouflage well into the forest floor.
The Aztecs called them turtle-rabbits. Spaniards dubbed them armadillos, which translates to “little armored ones.” In the American South, they’re known as opossums on the half-shell and Texas speed bumps.
To Ruby Osborne, a resident of Buchanan County, Virginia, in the far southwestern corner of the state, they were simply the nuisance that was digging up her flower beds.
At first, Osborne didn’t know the identity of the nocturnal visitor leaving her yard pockmarked with loamy soil. After several weeks of frustration, in early 2019, Osborne finally spied a potential culprit out her back window: An armadillo standing up on its hind legs, which Osborne called “plumb comical.” Her daughter snapped a photo of the armadillo scurrying away and sent it to the wildlife department.
The discovery was routed to Seth Thompson, a state wildlife biologist in nearby Wise. He was skeptical—until he looked at the photos.
“It never occurred to me that these animals would be out here,” he says.
With Osborne’s permission, he set a live trap to catch the animal, to no avail. It was only several months later, when Fies found an armadillo killed by a dog, that biologists could confirm the animal is living in Virginia. That specimen, kept at the Virginia Museum of Natural History in Martinsville, has a special status as the first scientifically described member of a species in the state.
Built for digging
On a warm May morning outside her office, Moncrief unzips a plastic bag containing the Virginia armadillo’s skeleton, a jumble of bones stripped clean by her lab’s colony of flesh-eating beetles. A whiff of formaldehyde fills the air as she pulls out the skull, jaw, pelvis, and several leg bones and lays them on a metal filing cabinet. At the top of the skull is a nail-size puncture, courtesy of the canine that ended its life.
Moncrief points to the armadillo’s small, peg-shaped teeth—expertly sculpted by natural selection to grind down a steady diet of insects, grubs, and other invertebrates.
The armadillo’s ability to find and eat such a wide variety of food is probably one of the main reasons it has been able to spread so far, so quickly, says Moncrief. Her office is littered with squirrel figurines and issues of the comic Squirrel Girl, evidence of her first research passion.
Moncrief picks up the armadillo’s shell, or carapace, which is made of keratin and is surprisingly light. Each piece of the armadillo’s armor is edged with tiny, sensitive hairs shorter than an eyelash that help the animal feel its way around underground tunnels. Its shell provides protection from predators, as does its leathery skin and tendency to jump several feet in the air when startled. That strategy may work against bobcats and coyotes, but is less effective against a vehicle, likely the armadillo’s leading cause of death in Virginia, she says.
It’s a pointed snout and claws, she adds, that allows the mammals to bulldoze deep into the earth—one of the reasons armadillos may not be welcome as neighbors.
“These burrows are essential for their survival,” says Brett DiGregorio, an ecologist at the University of Arkansas. “When they get down into these deep burrows, temperatures are stable, and they’ve got a safe place to sleep. They’re not wasting a lot of energy.” (Read why Appalachia’s wild rat is mysteriously disappearing.)
Armadillos can sleep in their burrows for up to 16 hours per day, leaving only in search of food or water. They aren’t especially social and generally only meet to mate.
Prolific breeders, females birth a litter of identical quadruplets between March and May. Babies stay with mom until they’re three to four months old, then strike out in search of new territory. At nine to 12 months of age, armadillos are ready to have pups of their own. DeGregorio suspects it’s these intrepid younger ’dillos that are leading the northward charge.
As for how they’re physically getting from place to place, Taulman found in a 1996 study that the animals may literally hitchhike in vehicles, climbing into the chassis or stowing away in the trunk.
A boon for other species?
Since Osborne’s experience, ecologists have gotten a few more complaints about armadillos digging into backyards, a phenomenon that’s likely to continue.
DeGregorio’s recent research, in the journal Ecology and Evolution, found that the armadillos’ activity levels in Arkansas are related to the presence of humans. Animals in areas with more people were more active at night, whereas those living further from towns and cities were more active in daytime—suggesting the mammals are more adaptable than previously thought.
There’s no tried-and-true strategy for dealing with garden armadillos, but McDonough advises such homeowners use a humane trap to relocate the animals or place some dog fur and feces near the entrances of their burrows to encourage them to move along.
Though armadillos’ effects on their non-native ecosystems is unknown, it may not necessarily be detrimental. As insect eaters, they could gobble up some agricultural pests, such as invasive Asian jumping worms, DeGregorio says. (Read why not all non-native species are harmful.)
Though they get a bad rap for digging up agricultural fields and gardens, this behavior creates valuable habitat for other animals. A May 2022 study led by DeGregorio in Arkansas documented 19 mammal species and 40 bird species, among other creatures, that used 35 armadillo burrows.
“Other animals that do this, the desert tortoise, the gopher tortoise, prairie dogs—we worship them as valuable ecosystem engineers,” he says.
“But we don’t give that level of respect to the armadillo, and I just would like to see that change.” As the species continues its journey northward, he hopes to get that chance.