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Wednesday, September 11, 2013

Little Armored One

Spanish for ‘little armored one’, the armadillo is one of the most interesting mammals in North America.  All but one of the 20 different species of armadillo live in Latin America, but the Nine-banded Armadillo (Dasypus novemcinctus) makes its home as far north as Texas (except for the western Trans-Pecos), Oklahoma, and Louisiana.  In fact, this armadillo is the official state small mammal of Texas!

A cat-sized, insect–eating mammal, armadillos have bony plates that cover their back, head, legs, and tail, protecting them from predators. No other living mammal wears such a shell, but contrary to popular belief, the Nine-banded Armadillo cannot roll into a ball and encase itself with its shell.  Only the Three-banded Armadillo can accomplish this, by curling its head and back feet inward and contorting its shell as protection.  No amount of armor can protect them from the cold, however, and because of their low metabolic rate and lack of fur and body fat stores, cold weather can wipe out whole populations of these little creatures.

Armadillos have a pointy snout and small eyes, and are prolific diggers.  They dig for food and dig many burrows, mostly along creekbeds in Central Texas, and they do not survive in areas where the soil is too hard to dig.     Armadillos spend up to 16 hours a day digging, mainly active in the dawn and dusk hours, looking for beetles, ants, termites, and other insects. Their eyesight is quite poor, but they use their keen sense of smell to locate food, and utilize their long, sticky tongues to grasp berries, caterpillars, grubs, fungi, and sometimes even carrion.  

Armadillos are quite fond of water, visiting water holes and streams to drink, feed, and even take mud baths.  Their specific gravity is high, which means they normally ride low in the water when swimming.  For short water crossings, they often just walk underwater across the bottom, but for deeper and longer crossings they voluntarily ingest air to inflate themselves and increase their buoyancy by retaining the air in their digestive tract! 

Armadillos are thought to be a pair during the breeding season, sharing the same burrow.  Due to their bony shells and the underside location of their genitalia, copulation occurs with the female lying on her back.  While breeding occurs in July, the embryo remains in a dormant state until November. Always of the same sex, identical quadruplets develop from the single egg, and four young are born in a grass-lined burrow in March.

While the Nine-banded Armadillo is a unique mammal whose range is expanding northward, there is reason to be concerned about their conservation status in Texas.  Encroaching human civilization, overgrazing, and progressive climatic change may be keeping them on the move, and many mammalogists agree that armadillos are rare at best when compared to populations of a few years ago.  This decline also appears to be correlated with increasing populations of feral hogs, as well as the propensity for people to make trinkets from armadillo shells.  Perhaps our state motto should read ‘Don’t Mess with Texas Armadillos!’