Armadillos roamed the Western Hemisphere during the Ice Age. But by the time naturalist John James Audubon first noted their presence in 1854, the mammals had just a tiny toehold north of the U.S.-Mexico border along Texas’ hot Rio Grande Valley, with a broader range across Mexico and countries farther south. Since then, armadillos have been ceaselessly marching north and east, with scientists citing climate change as a likely factor. The critters are tough to study, living much of their l…