Large vertebrate herbivores, when they find a salt-bearing layer of rock, say in a cliff face, can produce sizable voids where, over generations, they have removed and consumed salty rock. The cavities formed by this natural animal process constitute a unique class of caves that can be called salt ingestion caves. Several examples of such caves are described in various publications. An example in Mississippi U.S.A., Rock House Cave, was visited by the authors in 2000. It seems to have been formed by deer or bison. Perhaps the most spectacular example is Kitum Cave in Kenya. This cave has been excavated to a length over 100 meters by elephants. An ancient example is La Cueva del Milodon in Chile, which is reported to have been excavated by the now extinct milodon, a giant ground sloth. Still other possible examples can be cited. This class of caves deserves a careful definition. First, the cavity in rock should meet the size and other conventions of the locally accepted definition of a cave. Of course this requirement differs in detail from country to country, particularly in the matter of size. The intent is to respect the local conventions. The characteristic that human entry is possible is judged to be a crucial property of any recognized cave definition. Second, the cavity should be significantly the result of vertebrate animal consumption of salt-bearing rock. The defining process is that rock removed to form the cave is carried away in the digestive track of an animal. While sodium salts are expected to be the norm, other salts for which there is animal hunger are acceptable. Also some other speleogenesis process, such as solution, should not be excluded as long as it is secondary in formation of a cave in question.
Lundquist, Charles A. and William W. Varnedoe Jr..
Salt ingestion caves.
International Journal of Speleology,
Available at: http://scholarcommons.usf.edu/ijs/vol35/iss1/2