The Devil’s Den Fossil Site may have been Located in One of the Last Refuges of the Megafauna

The Devil’s Den fossil site is located near Williston, Florida in Levy County.  It’s a sinkhole that served as a natural trap between 9,000 BP and 8,000 BP.  Apparently, the sinkhole closed until a few hundred years ago when it reopened and began trapping animals again.  The sinkhole ranges between 5-90 feet below the average water table and accordingly is filled with water.  It also serves as a bat roosting site, explaining the numerous chiropteran remains.  Rainwater dissolving limestone bedrock creates sinkholes such as this one.

Location of Levy County (red), site of the Devil’s Den sinkhole.

The area immediately adjacent to the sinkhole originally consisted of a dense mesic forest of hardwood, but beyond this moist environment, a grassland savannah with widely spaced live oaks predominated.  Scientists believe this was also the type of environment that occurred here 9,000 years ago at the time of the fossil depositions.  Indians later periodically cultivated some of the land.  Though watermelons didn’t originate in North America, Indians in Florida grew large quantities of them from seeds they obtained from Europeans.  The earliest recorded use of the land around Devil’s Den was as a watermelon field.  The next owner used the sinkhole as a garbage dump.  By the time scientists were granted permission to excavate fossils here in the late 1960’s, it was in the middle of a cow pasture.  Today, it is a private resort and a destination for scuba divers and campers.  There are 4 chambers in the sinkhole that scuba divers enjoy exploring.  The excavated fossils came from chamber #3, but scuba divers report seeing fossils all over the bottom still.  

On lists of megafauna terminal extinction dates, the data from the Devil’s Den fossil site is always excluded.  I never understood this, but I think I’ve finally been able to piece together enough information to assume an answer.  H.K. Brooks wrote a research paper detailing the radiocarbon dates and the geological information that made him conclude the fauna from this site was between 7,000-8,000 years old.  As far as I can determine, this paper never was published, though the information has been mentioned in several published works including the one referenced below.  Because this information was never published in a peer-reviewed publication, it’s  disregarded by scientists arguing over the cause of Pleistocene megafauna extinctions. But that doesn’t mean the data is wrong.  One of the reasons he may have had a hard time publishing his data was because it contradicted the preconceived notion of when megafauna became extinct.  It also contradicted both competing models of megafauna extinction.  In 1974 most vertebrate zoologists believed climate change caused the extinction of the megafauna.  But the climate and environment of 9,000 BP in north Florida were about the same as it is during the present time.  Yet, many notable species of megafauna were apparently still extant.  His data also conflicted with Paul Martin’s sudden overkill “blitzkrieg” model of extinction in which he proposed all the megafauna were wiped out in a few hundred years between 12,000 BP and 11,000 BP.  Without either school of thought in his corner he found it impossible to get his data published.  The later extinction dates do fit within a protracted overkill model of extinction that had not yet been proposed or considered.  Evidence at Devil’s Den suggests declining populations of some megafauna, while others are already extinct.  This perfectly supports a model of extinction that includes gradual and haphazard human overhunting. SedaDNA found in Alaska permafrost also suggests younger extinction dates for megafauna than are commonly accepted.  (See: https://markgelbart.wordpress.com/2011/02/)

H.K. Brooks’ study was in 1974 before radiocarbon dating was recalibrated.  This means the dates of the fossils at Devil’s Den probably are from 8,000 BP-9,000 BP rather than 8000 BP-7,000 BP, but this is still 3,000 years younger than the commonly accepted terminal extinction dates of most megafauna species.

The Devil’s Den sinkhole.  Imagine a deer being chased by a dire wolf and falling in this hole.

Businessmen built a a stairwell down to the sinkhole, providing easier access for scuba divers. http://www.devilsden.com/  

If a person could go back in time and camp at this site 9,000 years BP, they would find a wilderness rich in wildlife.  Several species of megafauna may have already become extinct while others were in decline, yet they still existed.  Bison, horses, and flat-headed peccaries roamed the savannahs and rested in the shade of centuries-old live oaks.  Great droves of white-tail deer outnumbered all the other ungulates because they were better able to withstand human hunting pressure.  White-tail deer fossils were by far the most common of the ungulates at this locality.  This is unusual compared to other Pleistocene fossil sites in Florida.  Dr. Webb suggests competing tapirs, llamas, and long-nosed peccaries had become extinct by this time.  All of these species favored forest or forest edge habitat.  Without them deer had this niche to themselves.  Mastodons and Jefferson’s ground sloths browsed the moist woods.  A camper going on a hike would need to carry a firearm.  Saber-tooths, jaguars, and dire wolves still stalked the range.  Two species of bears might prove troublesome too, but by this time they probably had learned to fear man.  Paleo-indians and their dogs occasionally passed through here as well.  But the most common carnivore was the striped skunk.  Scientists found 36 striped skunk skulls at Devil’s Den.  Either they were abundant, or they had a knack for falling into sinkholes.  The same might be true for cottontail rabbits which left more fossils at Devil’s Den than any other animal.  Below is a list of mammal species recovered from the Devil’s Den fossil site. * denotes extinct species.

opossum

least shrew

short-tailed shrew

eastern mole

southeastern myotis bat

gray myotis bat

Florida yellow bat

eastern pipistrelle

human

*Jefferson’s ground sloth. (Dr. Webb erroneously considered the sloth fossil found here as Wheatley’s ground sloth.  Bjorn Kurten corrected this misidentification.)

gray squirrel

fox squirrel

southern flying squirrel

southeastern pocket gopher

old field mouse

cotton mouse

gopher mouse

golden mouse

rice rat

woodrat

cotton rat

meadow vole

pine vole

muskrat–Archaeological records suggest muskrats lived in Florida as recently as 3100 years BP.)

Florida round-tailed muskrat

*southern bog lemming

cottontail rabbit

*dire wolf

red wolf

domesticated dog

gray fox

raccoon

*Florida spectacled bear

black bear

long-tailed weasel

striped skunk

spotted skunk

bobcat

jaguar

*saber-tooth cat

*mastodon

horse

*flat-headed peccary

white-tailed deer

bison

In addition cows and pigs from more recent times had fallen in the sinkhole and they left bones.

Although a study of bird fossils from Devil’s Den was conducted, the results were never published.

J. Alan Holman did publish his study of reptile and amphibian fossils from Devil’s Den in Herpetologica 34 (2) in 1978.  The abstract of that paper claims 1 salamander, 5 species of frogs, alligators, 1 species of lizard, and 15 species of snakes were recovered here.  Devil’s Den is also the  youngest known record of both species of extinct giant tortoise–Hespertestudo crassicutata and Hesperotestudo incisa.

Reference:

Webb, David

Pleistocene Mammals of Florida

University of Florida Press 1974

Interestingly, in addition to discussing the site and the fossils, Dr. Webb came up with a long convoluted statistical analysis that allegedly showed how the evidence from Devil’s Den supported climate change as a cause of megafauna extinction.  His analysis came to the conclusion that the mass wave of extinction at the end of the Wisconsinian Ice Age was not unusual–a ludicrous claim.  Dr. Webb is retired now, but in his later work he did come to accept that man played an important role in the extinction of at least some of the megafauna.

Tags: cottontail rabbit, Devil's Den, flat-headed pecarry, Indian cultivation of watermelon, megafauna extinction, sedaDNA, striped skunk, white tail deer