Picture a game of whack-a-mole: a noisy arcade, frustration and elation building as toy moles appear and disappear at random. Now imagine the game is in Brazil, covering 140 square kilometers (54 square miles); the moles are a cryptic, loaf-of-bread-sized species of armadillo with a pig snout that dig perfectly round burrows; and there is no whacking involved.
The southern naked-tailed armadillo (Cabassous unicinctus squamicaudis) spends 99.25 percent of its time underground. If by chance you locate one above ground, it can dig away in a matter of seconds.
“They can re-emerge, it’s rare, but sometimes it happens, again for a few minutes,” says Gabriel Massocato, a biologist who monitored the species daily during the study.
Scientists are only now beginning to uncover some of its secrets, revealed in a recently published study in the Journal of Mammalian Biology — likely the first study devoted solely to this species’ behavior and ecology. Conducted by the Giant Armadillo Conservation Project of which Mossocato is a member, the research was supported largely by zoos and aquariums.
“They are literally living under our feet. You need to spend hours and hours waiting for them to pop up in the most unpredictable place,” conservation biologist Arnaud Desbiez, the study’s lead author and regional coordinator for Latin America at the Royal Zoological Society of Scotland (RZSS), told Mongabay by email. “They are really an adorable armadillo species with their pig-like snout, big ears and soft tail. Seeing one come out from under the ground is truly an amazing sight.”
Southern naked-tailed armadillos have a keen sense of smell and strong front claws, all important adaptations for an animal that constantly burrows into the earth. They also, like many other armadillos, have poor eyesight, an understandable adaptation to underground living. Very little else is known about this species.
“My first encounter with the species was through our camera traps when I saw one using a giant armadillo burrow,” Desbiez said. “It was the very beginning of the project and I had never seen one, despite working in the Pantanal for the past eight years. I was so surprised!”
The air of mystery surrounding this species led Desbiez and his team to seek out any information they could about its day-to-day activities and its natural history in Brazil’s Pantanal region, a vast area characterized by wide-reaching tropical wetlands.
“A sand mount, which [can] easily be confused with an anthill, can indicate that there is a very small, cute, cryptic and such charismatic armadillo living right under our feet,” Danilo Kluyber, a research associate of the Naples Zoo and Caribbean Gardens and co-author of the new study, told Mongabay in an email.
The sand mounts are formed by dirt pushed up by an armadillo burrowing underneath. As it digs, it folds its ears back and rotates its body, creating a near-perfectly rounded entrance to its burrow.
Among the factors that drive the southern naked-tailed armadillo underground are the termites and ants it feeds on, and the predators that feed on it.
There’s also the matter of offspring. Scientists have never observed the armadillos returning to the same burrow twice — with the crucial exception of a mother returning to her pup’s burrow. The researchers found that mothers return to their baby’s burrow until they are mature enough to change tunnels and eventually begin digging for themselves. Southern naked-tailed armadillos only have one pup at a time, according to the researchers, similar to other naked-tailed armadillos in the Cabassous genus.
A southern naked-tailed armadillo spends a grand total of 10 minutes a day above ground, on average, according to the study. As a result of this extreme underground living, Desbiez and his colleagues classified the species as subterranean, a term normally reserved for rodents such as the naked mole rat.
Unlike other species that Desbiez studies, such as the giant armadillo and the giant anteater, the southern naked-tailed armadillo is rated as being of least concern on the IUCN Red List. This makes it different from most of its armadillo cousins, more than half of which are considered threatened with extinction. Habitat loss is one of the greatest threats to many armadillos, and biodiversity in general, but not so for the southern naked-tailed armadillo.
“The good news is they seem to survive well in cattle pastures,” Desbiez said. “The area we worked in the ranch was the most degraded by pasture … it seems they can withstand a certain level of habitat alteration.”
This adaptability is a vital factor in their persistence. While other armadillo species are imperiled by the conversion of natural ecosystems into grazing land, this furtive species seems to subsist despite major changes to its natural landscape. Some 22,000 square kilometers (8,500 square miles) of the Brazilian Pantanal — an area roughly the size of the U.S. state of New Jersey — was modified or lost for intensive land use such as pastures and roads between 2008 and 2015. Indeed the study was conducted on the Baía das Pedras lodge and ranch. Part of the reason southern naked-tailed armadillos manage to thrive in cattle pastures is the fact that they so rarely venture above ground.
There is still much to learn about this species, including an estimate of its population size. The species’ estimated range is widening as researchers record its presence across Brazil, Paraguay and northern South America east of the Andes.
“As they live underground they are more common than we might first believe” Desbiez said. “It is actually pretty easy to detect if the animal is in the areas due to the characteristic holes it digs. Although they are hard to see, their burrows are easy to encounter. In the Cerrado” — the tropical savanna region of Brazil — “we see their burrows frequently.”
Despite the valuable new information gathered by Desbiez and his team, their observations spanned only 0.75 percent of each armadillo’s day: the portion of time spent above ground.
“We would love to understand how they navigate underground, especially in relation to temperature. Armadillos are considered imperfect homeotherms” — animals that maintain their own body temperature at a steady level — “and temperature [is] believed to influence their behavior,” Desbiez said. “Do they go deeper underground on very hot days, while staying beneath the surface on cooler days?”
The answers will have to wait for the next day at the arcade.
Banner image: A southern naked-tail armadillo. Photo courtesy of Giant Armadillo Conservation Project.
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