Armadillos

Moving back to Tennessee two years ago after three in Nebraska I was surprised to see that amongst the usual skunks, raccoons and deer one sees dead along the side of the road there were now armadillos. I have always found these strange little tanks fascinating since I first encountered them on Cumberland Island as a teenager. And now I lived somewhere that they lived! But we've lived in Tennessee off and on since 2004, and in all our trips to Nashville or even Memphis armadillos hadn't really been something I'd noticed before. Was I really that unobservant? So it was with curiosity and some self-disappointment that I began to dig deeper.

Armadillos aren't just a little weird. Most cladograms have their group, xenarthra, splitting off from the rest of placental mammals right at the beginning of the Cenozoic (like here). They're endothermic, but cold-blooded enough not to have external testicles and to contract systematic leprosy, a disease humans only get on our cooler extremities. They all start out as identical quadruplets rather than singlets or members of a polyzygotic litter. They mostly eat insects and can't open their mouths wide enough to bite you. Strange creatures indeed!

Time sometimes presents us with fortuitous events. Last month the Tennessean ran a story about the armadillo invasion currently occurring in Tennessee. Apparently it wasn't that I was unobservant, but that armadillos just got to Tennessee. The article also clued me in to Tim Gaudin, a professor at UT Chattanooga who was studying their invasion. So I contacted Tim, who was doubly excited about my interest and the fact that just that week a new monograph on armadillos was being released. The marketer in me wonders if it was merely fortuitous or if the story was a plant to generate interest in the subject and drive book sales. Either way I ordered The Nine-Banded Armadillo: A Natural History by Loughry & McDonough and have spent the past month making my way through it.

The radiation of placental mammals was set somewhat by geology - continental drift meant different branches of the tree developed in relative isolation from eachother. The onset of oscillations into and out of ice ages 2 million years ago at the start of the Quaternary brought this isolation to an end, but I digress. Xenartha, which includes sloths and anteaters as well as armadillos, developed in South America. On that continent there is a variety of species of armadillos, from the tiny burrowing pink fairy armadillo to the three-banded one which can roll up into a perfect sphere. The nine-banded armadillo is the sole variety to make the trek to El Norte so far. As recently as a century ago they had only made it as far north as southern Texas, but as insectivores who do really well in disturbed environments it's not a stretch to suppose that humanity has greased the works for their invasion.

Loughry & McDonough present not only this natural history, but also the anatomy, ecology, behaviors, and just about everything else we know about the biology of armadillos in their book. And, while not dumbing down the content, they write in a sufficiently humorous vernacular that it reads like conversation. I found myself wanting to become an armadillo researcher as the authors present a multitude of unanswered questions from the unknown chemical ecology of the smells which armadillos use to understand their world to the sampling bias of studies done in the US versus the historical South American habitat of the species. From a more meta-perspective one also takes away an excellent picture of what a successful invasive species looks like - and what is a startup but an invasive species looking to process resources more efficiently than incumbents in the ecosystem?