A cave is any naturally occurring void, cavity, recess, or system of interconnected passages beneath the surface of the Earth, or within a cliff or ledge large enough to permit an individual to enter, whether or not the entrance was naturally formed or man-made (The Federal Cave Resources Protection Act [FCRPA], Sec. 3[1]). Cave and karst resources are abundant in the Bighorn Basin. Karst topography consists of landforms produced by the dissolution of rock creating a variety of landscape features, including caves, which are common in the Planning Area. Cave and karst resources are fragile because of their association with other resources such as groundwater systems and biological communities. They also might be considered nonrenewable resources because of paleontological and archeological deposits, and speleothems (mineral formations inside caves) they contain.
In the Planning Area, the cave and karst system along the west slope of the Big Horn Mountains in the Medicine Lodge area is important due to mineral features such as speleothems, potential for diverse karst aquatic organisms, cultural and paleontological resources, and recreation opportunities. This area is hydrologically important because of the presence of disappearing surface water streams and its link to regional groundwater aquifers. This system includes rock outcrops of the Madison Limestone, Bighorn Dolomite, and Ten Sleep Sandstone, all of which are primary recharge areas for regional aquifers in the Bighorn Basin. A portion of this area is designated as an ACEC for the protection of cave and karst resources (refer to Section 3.7.1 Areas of Critical Environmental Concern for more information).
The FCRPA of 1988 was the first federal legislation to recognize caves and their contents as whole, integrated ecosystems. FCRPA declares significant caves on federal lands as an invaluable and irreplaceable part of the Nation’s heritage. U.S. Department of the Interior (DOI) implementation regulations for FCRPA require that federal lands be managed in a manner that, to the extent practical, protects and maintains significant caves and cave resources (43 Code of Federal Regulations [CFR] Part 37.2). BLM policy and guidance for managing cave resources is to protect sensitive, fragile, biological, ecological, hydrological, geological, scientific, recreational, cultural, and other cave values from damage and to ensure they are maintained for public use, both now and in the future (BLM 2008b).
Under FCRPA, a cave is considered significant if it meets one or more of the following six criteria:
Biota – The cave serves as seasonal or yearlong habitat for organisms or animals, or contains species or subspecies of flora or fauna native to caves, or is sensitive to disruption, or contains species found on state or federal sensitive, threatened, or endangered species lists.
Cultural – The cave contains historic or archeological resources included on or eligible for inclusion on the National Register of Historic Places (NRHP) because of its research importance for history or prehistory, its historical association, or other historical or traditional significance.
Geological/Mineralogical/Paleontological – The cave has fragile geologic or mineralogic features, features that exhibit interesting formations, or paleontological resources.
Hydrologic – The cave is part of a hydrologic system or contains water important to humans, biota, or development of cave resources.
Recreational – The cave provides or could provide recreational opportunities or scenic values.
Educational or Scientific – The resource offers opportunities for educational or scientific use or is in a virtually pristine state, lacking evidence of contemporary human disturbance or impact, or the length, height, volume, total depth, or similar measurements are notable (43 CFR Part 37).
There are 32 known caves in the Planning Area, of which 19 are considered significant according to FCRPA criteria (BLM 2009b). Eight caves are gated and locked and three caves are open through the issuance of a key and permit. Recreational use of these caves is minimal, except by local cave enthusiasts. Horsethief, Spirit Mountain, and Great Expectations caves typically experience the highest level of recreational use. The BLM manages all caves in the Planning Area in a wild state; there are no developed caves on public lands in the Planning Area. Bats use several caves in the Planning Area and the BLM lists three of those bat species (Townsend’s big-eared bat, spotted bat, and long-eared myotis) as sensitive.
Management challenges for cave resources include preventing degradation of the resources while allowing for recreational use and scientific research.