129-77 Ground Penetrating Radar Comparison of Late Pleistocene Rodent Burrows and Modern Burrow Systems of Prairie Dogs

Abstract:

Prairie dogs, genus Cynomys, inhabit a large portion of the western central United States and have been extant for approximately 2 million years, first appearing in the late Pliocene. These burrowing ground squirrels are known for their complex social structures, sophisticated methods of communications, and keystone position in the ecosystem. This work presents a comparison of the ground penetrating radar (GPR) results of surveys of three modern burrow systems of Cynomys gunnisoni near Taos, New Mexico and a Late Pleistocene rodent burrow system west of Bernalillo, New Mexico in the Ojito Wilderness within the Jurassic Todilto Formation.

The modern burrow systems are in two zones of distinct geology. Alluvial fan deposits comprise the first zone within the town of Taos, while the second zone is east of Taos at Valle Escondido Golf Course, with one burrow system adjacent to a fairway and another directly beneath a fairway. Each of these modern burrow systems are active, with prairie dogs visibly maintaining the entrances. The Pleistocene burrow system is in Todilto Formation gypsum with burrows infilled by fine-grained siliciclastic sediments of Pleistocene age. The current surface exposure clearly shows one level of burrows radiating in multiple directions, with evidence of mammoth tracks crosscutting the burrows.

GPR results from both the modern and the ancient burrow systems show complex networks, with tunnels in multiple directions and inclines. While the geophysical results with the alluvial fan deposits are very noisy due to the poorly sorted clastic sediments and several anthropogenic disturbances, the sediments at the golf course are much more conducive to GPR surveying, producing a greater signal to noise ratio. Burrow entrances are clearly imaged with the upper level of the burrow system distinctly shown in the modern systems. Results show inclined and branching tunnels, multiple connections between entrances, and possible chambers. Deeper levels are challenging to identify in the GPR data from the modern burrow systems, with only faint traces visible. The ancient burrow system shows at least one level of burrows below the surface expression of the burrow system.

Although limited by the depth of penetration of the equipment used, results demonstrate similarities shared by both ancient Pleistocene age rodent systems and modern prairie dog burrows, suggesting complex social behavior of the Pleistocene burrow makers.

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