MORPHOLOGY AND SURFICIAL CHARACTERISTICS OF SMALL MAMMALIAN BURROWS, CAPITOL REEF NATIONAL PARK, UTAH

Small-diameter mammal burrows, interpreted as ground squirrel domiciles, are studied in recently exposed cut banks of dry wash within Capitol Reef National Park, Utah. This network of open burrows show both horizontal and inclined orientations, with superb internal ornamentation from abundant scratch marks. The horizontal burrows are located within Entisols developed on Quaternary terrace deposits, and are found 40 cm below the soil surface. The sediment comprising the cut bank is poorly sorted and ranges from 1.0-3.0 phi in grain size. The burrows are triangular with rounded edges and have flat bases that rise into a rounded arch at the top of the burrow structure. The burrows range from 5 cm to 8.8 cm in height, with an average height of 6.6 cm. The width of individual burrows are between 5.5 cm to 9 cm. At least two burrows are interconnected, which was determined with the use of a flashlight. Individual burrow segments are up to 52 inches in length, but this is considered a minimum value as the complete burrow network was not excavated. The burrows are observed to branch at angles of more than 90 degrees, but exposures do not allow branches to be examined in detail. In some burrows, branches were observed to terminate quickly (i.e., knobs) and may indicate an abandoned attempt by the tracemaker to create a new branch of the burrow.

The surficial morphology of the burrow’s interior is not smooth, and instead show abundant ornamentation. These features usually occur as clusters of 3 elongate-to-curved grooves separated by ridges. These are limited to the sides and roof of the burrows where they cover the entire exposed surface; the floors of the burrows are covered by a thin (mm thick) layer of sand which hides the surficial morphology of the burrow floor. These ornamentations are interpreted as scratch marks from the claws of the tracemaker. The scratch mark clusters appear at completely random orientations: the claw marks range anywhere from 15° to 78° to off the horizontal axis. The scratch marks clusters have an average length of 2.7 cm, width of 1 cm, and relief of 2-3 mm. Individual scratch marks are 1 mm in width and are separated by positive relief ridges 2-3 mm in width. The various orientations of the claw marks are interpreted to reflect the tracemaker rotating along its back and side as it continuously scratched and reworked the burrow walls.