Why do armadillos move north?

ROANOKE, VIRGINIA – When Nancy Moncrief began her job as a curator of mammalogy at the Virginia Museum of Natural History in Martinsville in 1989, she figured the number of species under her care would not change over the course of her career. And for twenty years, his hypothesis seemed to be confirmed.

But 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,” was the subject line. Fies’ colleagues had found evidence of an armadillo two months earlier, but they had failed to catch the animal to confirm it.

Moncrief, who studied at Louisiana State University, was familiar with nine-banded armadillos native to Central and South America as well as parts of the United States, including Texas. . She replied to Fies: “But what are they doing in Russell County ??”

There is no clear answer to this question. But what is certain is that these mammals, each weighing about 5.5 kilograms, have been moving steadily to the northeast for a hundred years, crossing the Rio Grande River in the 1850s and the Mississippi during the Great Depression. In the 1990s, they arrived in Tennessee, then North Carolina, and now Virginia.

“It was a real surprise,” says Moncrief, who published his findings on Virginia’s first confirmed armadillo in 2021 in the journal Southeastern naturalist. “It is a wave of expansion to the north. »

By May 2022, several further observations of armadillos in Virginia had been reported to Moncrief, though she could not say with certainty how many individuals of this species, which are closely related to sloths and anteaters, were present in the state, and how extensive they were. Officials in neighboring Maryland and West Virginia have not reported any sightings.

Still, several studies suggest that armadillos, which prefer warm climates, may one day grow as far north as New Jersey and Pennsylvania, especially due to warmer winters. In the northeastern United States, temperatures rose by 1 ° C between 1895 and 2011 and may rise by a further 5 ° C. by 2080.

“People have always predicted that this point would not be passed, and they always continued,” said Colleen McDonough, an ecologist and armadillo expert at Valdosta State University in Georgia.

“When warmer temperatures are observed further north, armadillos could potentially end up in areas where they would never have been expected twenty years ago.”

SUPER HIGHWAYS TO ARMADODOS

James Taulman, a retired ecologist from the University of Park, Missouri, began studying the expansion of the armadillo area in the 1990s.

It is still unclear whether the spread of this animal is due to its natural expansion, warming temperatures due to climate change or both, he says. But there is no doubt that these digging insectivores adapt very easily to new habitats.

“It does not take many armadillos to create a population. A female and her male offspring are enough, ”says Taulman. If the area suits them (wet soil, rich in insects and mild winters), they can thrive. »

Yet there are limits to the spread of the animal, McDonough says: for example, it can not go much further west than Texas because the soil is too dry to accommodate the number of insects needed for its survival.

According to her, cold temperatures and other unknown factors could also limit the colonization of the northeastern United States by armadillos.

In Virginia, the wrinkled bedrock, dense hardwoods and abundant streams of Appalachia seem far removed from the arid, open environment we imagine the armadillo is a habitat for.

According to Moncrief, it is actually the perfect habitat: they prefer to move along shady rivers and streams, where the abundance of food, shelter and moisture creates what she calls a super-highway for tattoos.

One recent spring morning near Abingdon, I parked my car on the shoulder of a winding country road to take a closer look at a series of shallow earth holes near a small creek: the signs that Moncrief and Fies had asked me to look for in my search for a armadillos.

A sudden rustle of leaves made my head spin. At 10 a.m., I knew the odds of seeing this nocturnal creature the size of house cats were low, and the noise was actually coming from a gray squirrel. Unless you have one of these in your garden, it is usually difficult to see armadillos, which are shy and camouflage well in the forest floor.

A FANTASTIC VISIT

The Aztecs called them rabbit turtles. The Spaniards of armadillos, referring to the solid shield that protects them like an armor. In the southern United States, they are called half-shell opossums and Texas humps.

For Ruby Osborne, who lives in Buchanan County, Virginia, in the far southwestern part of the state, they were simply a nuisance to dig up her flower beds.

At first, Mrs. Osborne did not know the identity of the nocturnal visitor, who left many holes in her clay-filled garden. In early 2019, after weeks of frustration, she finally spotted a potential culprit through her back window: a armadillo standing on its hind legs, which she called “really comical.” His daughter took a picture of the fleeing animal and sent it to the wildlife department.

The discovery was passed on to Seth Thompson, a wildlife biologist in nearby Wise. He was skeptical until he saw the pictures with his own eyes.

“It never occurred to me that these animals could be here,” he says.

With Mrs. Osborne’s permission he set a trap to catch the animal, without success. It was not until several months later, when Fies found an armadillo killed by a dog, that biologists could confirm that the animal was actually present in Virginia. This specimen, housed at the Virginia Museum of Natural History in Martinsville, has a special status as it is the first member of a species scientifically described in the state.

USOCIAL HITCHICKERS

One hot May morning, outside his office, Moncrief opens a plastic bag containing the skeleton of the Virginia armadillo, a mass of bones cleansed by the colony of carnivorous beetles in his laboratory. The smell of formaldehyde fills the air as she removes the skull, jaw, pelvis and several bone bones and places them on a metal cabinet. The top of the skull shows a puncture the size of a fingernail, caused by the dog that ended its life.

Moncrief shows the armadillo’s small teeth, skillfully sculpted by natural selection to grind insects, larvae and other invertebrates that make up its diet.

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