80 Kenneth T. Wilkins 



Yet, their presence does offer clues in reconstructing certain aspects of 

 the paleoenvironment. 



Bats. — The two species of bats recorded as fossils at Rock Springs 

 are usually considered obligate cave-dwellers, although alternate roosts 

 are also used (Barbour and Davis 1969). Their presence suggests a 

 reduced piezometric surface. No modern records of M. austroriparius 

 are known from the Rock Springs cavern, although the species is 

 reported from various northwestern Orange County caverns in the 

 immediate vicinity (Rice 1957). The present water level in the Rock 

 Springs cavern is probably too high to accomodate sizable colonies of 

 bats. Additionally, bat bones are quite delicate; that most of the fossil- 

 ized bat material is intact suggests the absence of flowing water in the 

 cavern during the depositional intervals. Yet, some water was probably 

 on the cave floor during occupation by Myotis austroriparius. This is 

 perhaps the most abundant extant bat species in Florida and it resides 

 in caves with either still or flowing water beneath roosting sites. Avian 

 remains from Rock Springs also showed Httle evidence of water-wear 

 (Woolfenden 1959). As with many other stream deposits, the context 

 and associations of fossil specimens is unknown and cannot be recon- 

 structed. However, the similarity of preservation of both Mormoops 

 and Myotis fossils indirectly suggests that occupation of the cave could 

 have been contemporaneous. 



Pocket gophers. — The contemporaneous occurrence of two con- 

 trageneric pocket gopher species in a fossil deposit was previously 

 reported by Dalquest and Kilpatrick (1973). They interpreted their cave 

 deposit (Shulze Cave, early Holocene, Edwards County, Texas) as the 

 roost of barn owls that foraged over a broad area, including the differ- 

 ent habitats occupied by Thomomys bottae and Geomys bursarius, 

 which had mutually exclusive microgeographic distributions. It is quite 

 possible that the Rock Springs cavern served as an owl roost during 

 times of reduced water table levels. Fossil barred owls, Strix varia, are 

 known from Rock Springs (Woolfenden 1959). Lack of stratigraphic 

 context disallows determination of whether Geomys and Thomomys 

 occurred contemporaneously in the Rock Springs vicinity rather than 

 being members of faunas of different time intervals. Nevertheless, the 

 mere presence in the fauna of the two species of pocket gophers allows 

 inferences regarding soil characteristics. Miller (1964) examined soil 

 preferences and competitive interactions of three genera of pocket 

 gophers in Colorado. He found that Geomys species required deeper, 

 sandier and more friable soils than either Pappogeomys species (includ- 

 ing Cratogeomys species) or Thomomys species. Thomomys, in con- 

 trast, was well suited to shallow, gravelly, less friable soils, although 

 Thomomys could and would inhabit deeper soils where available. 

 Requirements of Pappogeomys were intermediate to the other genera. 



