NEOICHNOLOGICAL OBSERVATIONS OF THE FORAGING PITS OF THE NINE-BANDED ARMADILLO (DASYPUS NOVEMCINCTUS) AND IMPLICATIONS FOR INTERPRETING CONICAL TRACE FOSSILS IN PALEOSOLS

The nine-banded armadillo (Dasypus novemcinctus) is often regarded as a pest because of the extensive damage individuals can cause to residential lawns. Much of this damage results not from tunneling in the subsurface, but from construction of numerous surficial pits while foraging for soil arthropods. Vertebrate foraging pits have received little ichnological attention, but ecological studies have shown that this feeding strategy results in downward-tapering, conical pits and is employed by such extant vertebrates as armadillos, rodents, monitor lizards, and echidnas. The purpose of the present study is to investigate the foraging pits constructed by D. novemcinctus to identify features that may be diagnostic of the species, as well as to aid in the recognition and interpretation of ancient foraging pits preserved in paleosols. Observations of armadillo activity were initiated following the appearance of foraging pits on a residential property in Lafayette County, Mississippi. An armadillo was visually confirmed as the tracemaker of the pits on several occasions. All observed foraging activity was nocturnal and involved a single individual. One large-diameter dwelling tunnel and three smaller, shelter burrows were associated with foraging pits. Ten plaster casts were recovered from the pits; these were measured and digitized to quantify volume and surface area. The plaster casts are elliptical conical to subconical in shape. Many cast surfaces contain scratch marks, the most distinct of which are short, paired, parallel groove casts likely resulting from digging with digits II and III; these digits are substantially longer and have larger claws than the other digits on the forelimb. The plaster casts are compared to three downward-tapering conical structures originating from a single bedding plane between a sheet sandstone and a red mudstone paleosol in the Upper Jurassic Morrison Formation, Garfield County, Utah. The conical structures are the same lithology as the sheet sandstone and have rare parallel scratch marks. The geometries of the sandstone structures are strikingly similar to those of the armadillo pit casts. I interpret the Morrison structures as vertebrate foraging pits, although they are not attributable to armadillos because the armadillo body-fossil record extends to the Late Paleocene.