The Nine-banded armadillo (Dasypus novemcinctus) is the only armadillo species whose range has extended into the United States. This mammal is an exceptionally powerful excavator, possessing physical adaptations that make the rapid displacement of soil a fundamental part of its daily existence. The capacity to dig allows the armadillo to shape its environment to meet its needs for survival, from obtaining sustenance to regulating its body temperature.
The Primary Reasons for Excavation
Armadillos dig for dual, survival-focused purposes: obtaining food and creating a stable environment for themselves. As an insectivore, the armadillo relies on a powerful sense of smell to detect prey, often locating invertebrates like grubs, ants, and worms several inches beneath the soil surface. They use their specialized claws to rapidly excavate the ground and expose the insect or larva, making foraging a constant act of digging.
The second reason for digging is to establish shelter, which is particularly important for regulating the armadillo’s body temperature. Due to their low body fat and thin armor, they are poorly equipped to handle temperature extremes, making burrows a necessity for survival. During the cold winter months, armadillos may spend up to 65% of their time underground to escape freezing temperatures. Conversely, in the summer, they retreat into the cooler, subterranean environment during the day to avoid extreme heat. Burrows also offer a reliable defense mechanism, allowing an armadillo to quickly wedge itself into a pre-dug tunnel or rapidly dig a shallow depression to lodge its armored shell against a predator.
Specialized Digging Tools and Technique
The armadillo’s efficiency as an excavator is due to specific anatomical features that transform its forelimbs into powerful digging tools. Its front feet are equipped with four toes, each bearing a long, non-retractable claw that acts like a miniature shovel. Powerful muscles attached to the scapula and humerus provide the leverage needed to loosen and displace compacted soil.
The digging process involves using the snout and forelimbs to loosen the dirt, which is then swiftly kicked backward by the hind legs. This intense activity requires a physiological adaptation to prevent the inhalation of soil particles. Armadillos possess the ability to hold their breath for up to six minutes, an adaptation that allows the animal to keep its snout submerged in the soil while foraging without breathing in dust.
Distinguishing Feeding Pits from Residency Burrows
The activity of an armadillo leaves behind two visibly distinct types of holes, each serving a separate function.
The most common sign of foraging is the presence of numerous small, conical depressions known as feeding pits. These pits are typically shallow, measuring about one to five inches deep and three to five inches wide. They are characterized by their downward-tapering, asymmetrical shape and represent the precise location where the armadillo’s snout and claws quickly dug to extract a detected invertebrate.
In contrast, residency burrows are the animal’s large, cylindrical homes used for sleeping, safety, and raising young. The entrances to these permanent shelters are noticeably larger, often measuring eight to ten inches across, and are frequently concealed by dense vegetation, fallen logs, or under structures like sheds and patios. The subterranean tunnel itself can be extensive, ranging from two to twenty-four feet long, though the average length is closer to three or four feet, and can reach depths of up to five feet. A single armadillo may maintain a complex territory with five to ten separate burrows, though only one serves as its primary dwelling.