Why are armadillos moving up north?

Reporter Giselle Roden explains that a “signal species” is an organism whose presence or absence reveals changes in an ecosystem, including rising temperatures or disappearing habitat. The nine-banded armadillo is increasingly appearing in Louisville and elsewhere in Kentucky: first recorded in LaRue County in 1986, it has since reached 63 of the state’s 120 counties. Its historic range includes the deep South, Texas, New Mexico, Mexico, and South America, but Kentucky’s average temperatures have risen nearly three degrees since around 1970. Milder winters have helped armadillos expand into Tennessee, Indiana, Ohio, and even Southern Illinois.

Biogeographer Anderson Feijó says there are currently 25 armadillo species, and the animal commonly called the nine-banded armadillo in the United States was recently recognized as the Mexican long-nosed armadillo. Armadillos occupy remarkably varied habitats, from the Amazon and South American dry forests to wetlands and mountains. The species in North America is a relatively recent arrival, first recorded in the United States in the 1850s. Feijó’s research found that North American armadillos eat a broader range of foods than populations in their native range, where they rely more heavily on insects. That omnivorous diet likely helped them survive and keep moving north.

Flora asks whether the expanding armadillos should be considered invasive and whether they could reach Maine. Feijó says their expansion has the typical pattern of invasive behavior: after first colonizing Texas in the 1850s, they remained mostly in the warmer South for decades, then continued spreading. Earlier estimates repeatedly underestimated them, and Feijó would not be surprised if they reached the Canadian border within 50 years as conditions continue changing. He presents that forecast cautiously but gives the animals credit for repeatedly exceeding expectations about how far they can travel and what environments they can tolerate.

Feijó identifies the carapace, or armor, as the armadillo’s signature feature and is studying whether armor strength corresponds to predators’ bite force. He once watched a domestic dog completely break an armadillo’s carapace, suggesting the armor is not an absolute defense. Nine-banded armadillos give birth to four genetically identical offspring every time, a trait used in research on human twins; some related long-nosed species produce as many as 12 identical offspring. The screaming hairy armadillo makes a loud whoop when held, apparently startling predators into releasing it. Armadillos also use powerful burrowing limbs to jump about five feet when threatened.

The five-foot jump can become dangerous near roads: when an armadillo hears an approaching car at night, it may leap to evade it but sometimes jumps toward the road, contributing to many road deaths. Feijó also confirms that armadillos can carry leprosy and advises people not to pick up wild animals, especially injured or bleeding ones, because handling them can expose people to disease. He closes with his favorite species, the tree-banded armadillo, the only armadillo that can roll into a ball. After working in Brazil for more than 20 years without seeing one, he drove 12 hours on vacation to a place where they were common and excitedly photographed them while local residents wondered what made the animal so special.