FRIESENHAHN CAVE. Friesenhahn Cave is a fossil-rich one-room cave, once named Bulverde Cave and Bone Cave, located west of U. S. Highway 281 in north central Bexar County. The cave is a sinkhole formed in the region’s karst topography. The only entrance, as documented since the earliest twentieth-century explorations, is a vertical twenty-eight-foot shaft. The floor of the cave is relatively flat, measuring thirty by sixty feet, with a seven-foot ceiling.
Due to the wealth of bones and fossils discovered at the site, George Veni in The Caves of Bexar County described Friesenhahn Cave as “one of the most important paleontological sites in the United States.” Concordia University, the institution that is the cave’s steward, has reported that, besides the La Brea Tar Pits in Los Angeles, “no site in the United States has yielded a greater variety of significant Pleistocene vertebrate fossils.”
Paleontological excavations have started and stopped for over a century at the Friesenhahn Cave; at times, decades have passed between excavations. The first known description of the cave was a survey conducted in December 1915 by D. V. Schuchardt, a student of the Agricultural and Mechanical College at College Station (now Texas A&M University). He estimated that the floor of the cave was covered in three feet of fossil-bearing material. Schuchardt collected samples from eighteen species that were forwarded to the United States National Museum (now the Smithsonian’s Arts and Industries Building) in Washington, D.C.
In June 1919 geologist E. H. Sellards in The Geology and Mineral Resources of Bexar County, a geology bulletin published by the University of Texas, described vertebrate fossils found in a cave on the “property of Mr. A. [Albert] Friesenhahn.” Sellards stated that the location of the cave was known for years prior, and bones of small animals, an elephant, and saber-tooth tiger were reported.
In the late 1940s and early 1950s a Texas Memorial Museum team at the University of Texas excavated the site. They discovered one complete adult and two complete juvenile scimitar-tooth Homotherium serum (saber-toothed) cats. Since the cave experienced little disturbance over the thousands of years after their deaths, the saber-toothed skeletons remained well-preserved. Research determined that the original cave entrance slanted to the surface, which allowed saber-toothed cats to use it as their home.
Additional academic research was conducted at the cave through the 1970s. In the late 1990s Concordia University in Austin began excavations. In 1998 the university became owner and steward of the cave and 3.5 acres of surrounding land through a gift of a parent whose daughter once attended Concordia.
The length of time that the saber-toothed cats used the Friesenhahn Cave as their home is unknown, although the last cats perished approximately 11,700-13,000 years ago. Excavators have reasoned that the cats carried or dragged prey into the cave. A large number of juvenile mammoth (Mammuthus columbi) teeth and bones have been found. The presence of such remains suggests that the scimitar-toothed cats selectively hunted young mammoths as a primary food source. Animal remains that have been discovered in the cave floor and walls include the American mastodon, tapir, bear, and deer. More than thirty genera of late Pleistocene Epoch (Ice Age) mammals, reptiles, and birds have been found. A least nine genera of fossil rodents were found in the cave in multiple layers of deposits. The large number of rodents possibly represents animals that used the cave for shelter, were searching for food, or were prey of larger mammals. Other significant findings at Friesenhahn Cave include a rare fossilized turtle shell of the Geochelone wilsoni, and the long-nosed peccary Mylohyus nasutus.
Pieces of flaked flint, polished bone, and a large freshwater clam were found in the cave and in the surrounding area. The plano-convex-shaped flint possessed similarities to flint scrapers used by Paleo-Indians. There remains a distinct possibility that early man lived in the area and entered the cave.
Research suggests that the sloped entrance of the cave was eventually filled by rock and debris, cutting off access. Sediments found on the floor of the cave suggest it was inaccessible for thousands of years, until the roof caved in, creating today’s vertical entrance.
Excavations continue at the Friesenhahn Cave as funding allows. Due to the layout and steep vertical entrance, the cave and the surrounding property are closed to the public and available only for paleontological researchers.
The three scimitar-tooth cats discovered in Friesenhahn Cave are on display in the Hall of Geology and Paleontology at the Texas Memorial Museum on the campus of the University of Texas at Austin.