The Rodent Fossils Found in Kingston Saltpeter Cave

When a new Pleistocene-aged fossil site is discovered, the average layman is likely to be most impressed with the fossils of the large extinct species, but scientists are often more excited about finding the remains of the smaller species.  Large mammals usually have wide ranges and can survive in a greater variety of habitats than smaller animals.  It’s hard for scientists to determine the paleoenvironment of a fossil site based on just the bones of larger species, but most smaller species require specific habitat types.  The composition of smaller species helps scientists better understand what the environment was like at the site during the time of fossil deposition. This explains the value of the Kingston Saltpeter Cave site in Bartow County, Georgia where many fossils of small mammals, reptiles and amphibians, birds, and even fishes were found.

Location of Bartow County, Georgia and Kingston.

Photo of the entrance of Kingston Saltpeter Cave.  It’s part of a 40 acre Nature Preserve protected by a private organization.  It’s generally closed to the public due to vandalism.

http://www.youtube.com/watch?v=5Qy93sGu6sg

The above link is a video slideshow of Kingston Saltpeter Cave.

Radiocarbon dating of white tail deer and long-nosed peccary fossils found in the cave produced dates of 12,400 and 12,700 years BP, roughly translating to 15,100 calender years BP.  During this time period, a rapidly warming climate was bringing an end to the Ice Age.  Many species that favor cooler climates still occurred in Georgia then, probably as relic populations.  The environment around Kingston Saltpeter Cave at the time the fossils became deposited has been interpeted as being mostly old growth deciduous forest but with some open woodland, grassland, and wetland nearby. Oak leaves, acorns, hackberry seeds, and charcoal were found in the fossil deposit but were never formally studied.  This is evidence of hardwood forest and forest fires.  I suspect oak trees were beginning to replace the northern species of pine and spruce that predominated here during the Last Glacial Maximum, and forests were expanding at the expense of the more extensive grasslands that occurred during the height of the Ice Age.  However, fossils of prairie chickens and upland sandpipers from this site show that small prairies still existed in the vicinity, and the continued presence of red squirrels suggests jack and white pine, and spruce  trees were still extant.

Kingston Saltpeter Cave served as a roost for at least 3 species of owls, including screech (Otus asio), probably a long-eared (Asio sp?), and a very large unknown extinct species (Strigidae sp?).  See https://markgelbart.wordpress.com/2013/04/22/the-unknown-owl-of-pleistocene-georgia/

Long-eared owl (Otus asio).  This is probably 1 of the at least 3 species of owls that roosted in Kingston Saltpeter Cave during the Pleistocene.  The fossil material found here can not definitively be differentiated from that of the short-eared owl.

The owls preyed upon at least 17 species of rodents (along with cottontail rabbits, other birds, and reptiles), leaving their remains in what eventually became a fossil deposit covered with rock that fell from the ceiling of the cave.  This collection of small mammal remains probably represents most, if not all, the rodent diversity found in north Georgia about 15,000 years ago.  Several of these species no longer occur in the region.  The eastern heather vole (Phenacomys ungava) no longer occurs farther south than Canada, but during the Ice Age, its present day range was completely inundated by glacial ice.  Evidentally, its range shifted far to the south.

Distribution of Phenacomys ungava

Present day range of the eastern heather vole.  This range was uninhabitable glacier during the Ice Age.  It lived as far south as Georgia then but in low population densities.

Eastern heather vole

The heather vole has been found at other fossils sites in the south but always in low numbers.  The modern southern range limit of the red-backed vole (Cletheromys gapperi)  is extreme northeastern Georgia, but it must have been fairly common in the state during the Ice Age.  Fossils of at least 10 individuals were found in the cave, and they’ve also been found at the Little Kettle Creek site in central Georgia.  The southern bog lemming (Synaptomys cooperi) was abundant as far south as Florida during the Ice Age but no longer occurs farther south than the North Carolina mountains.

Southern bog lemming.  Specimens from at least 17 individuals were found in the cave.  It’s not a true lemming.

The prairie vole (Microtus orchrogaster) currently lives just to the northwest of Georgia, but during the Pleistocene it lived in much of the state–specimens from at least 10 individuals were found in the cave.  Today, meadow voles (M. pennsylvanicus) are rare in the southeast and absent from the coastal plain, though a disjunct population occurs in 1 county in central Florida.  However, they were common in the region during the Ice Age–remains of at least 37 individuals were found in the cave, suggesting they were the most common rodent species in the vicinity then.  The reason for this species’ extirpation in the present day south is a mystery.  Studies show it is not adversely effected by the heat.  Cotton rats occupy the same type of habitat, but there seems to be no direct competition between these 2 species.  Pine voles (M. pinetorum) are the most common vole in Georgia today, and they were almost as abundant as meadow voles in the fossil record of the cave.

Owls left evidence of at least 3 northern flying squirrels (Glaucomys sabrinus) in the cave.  This species no longer occurs south of the North Carolina mountains.  However, southern flying squirrels (G. volans) were far more abundant–remains of at least 17 individuals were left by owls.  Although southern flying squirrels may very well have been the most abundant squirrel species in the vicinity then, this isn’t necessarily the case.  Flying squirrels are nocturnal, making them  more vulnerable to owl predation than other species of squirrel.  Their presence is evidence of old growth hardwood forests.  Specimens from at least 3 red squirrels (Tamiascirius hudsonicus) and 2 gray squirrels (Scirius carolinensis) were found in the cave.  The presence of the former indicates relic boreal conifer forests, while the latter indicates dense oak forests.  Eastern chipmunks (Tamias striatus) were represented in the cave as well.

Red squirrels were possibly just as common as gray squirrels in north and maybe even central Georgia during the Ice Age.  They favor boreal conifer forests which were more widespread then.

Leslie Fay, the scientist who identified the rodent fossils found in this cave, was unable to definitively distinguish to a species level mice in the genus Peromyscus.  This genus includes white-footed mice, cotton mice, deer mice, and oldfield mice.  Nevertheless, remains of mice from this genus were abundant in the cave. Owls brought woodrats (Neotoma floridanus) into the cave, but the low numbers of this species suggests they didn’t occupy the cave itself. Fossils of a few larger rodents were also collected from the cave–beaver (Castor canadensis), muskrat (Ondatra zibethicus), and woodchuck (Marmota monax).  A tributary of the Etowah River flows less than a mile from the cave, and the river itself is barely more than a mile away.  This is why aquatic forms are found among the cave fossils.  Perhaps a large mammalian predator dragged the beaver inside.

By comparison, only a few large mammal fossils were discovered in the cave, including those of several individual white tailed deer and long-nosed peccary.  These were likely the most common large ungulates of old growth forests.  One horse leg bone was uncovered as well.  A single jaguar died in the cave.  Perhaps this individual jaguar dragged the deer, peccary, and horse into the cave.  Several black bears may have used the cave for hibernation and died in their sleep, explaining why their fossils accumulated here.  Somehow, a fragmented tooth of an American mastodon washed into the cave–scant evidence of an animal that commonly foraged up and down the Etowah River.  It’s not clear whether the elk bone found in the cave was part of the fossil deposit or of more recent origin.

Reference:

Steed, Joel; and Larry O. Blair

The Late Pleistocene Record of Kingston Saltpeter Cave, Bartow County, Georgia 

Kingston Saltpeter Cave Project 2005

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