The Pleistocene Great Smoky Mountains

I renewed my subscription to the Southeastern Naturalist, so I could read a recent monograph that inventoried the mammal fauna of the Great Smoky Mountains National Park.  According to this paper, 68 species of mammals have been documented in the park, and 1 scientist predicts an additional 4 species might eventually be found there.  I suspect this number is greatly exaggerated–many of the species are small animals not documented in the park since the initial survey when the park was established in the 1930’s.  Those species not documented recently could very well be extirpated from the park.  The flora of the Great Smoky Mountains National Park is impressive but don’t plan a trip and expect to see much wildlife.  I visited the park once and saw just 1 squirrel and no other mammals besides lots of people.  There are 24 species of insectivores and bats allegedly inhabiting the park.  These species are difficult to see and enjoy.  That leaves 44 species and of these only 5 are considered megafauna (animals weighing over 40 pounds). The “big 5” are white tailed deer, elk, black bear, wild boar, and coyote.  The latter 2 are considered invasive, but I think of the coyote as a native species that is recolonizing former territory occupied during the Pleistocene.

There are probably more white tailed deer outside the park in the surrounding farmland.  White tailed deer prefer forest edge habitat, and most of the park has succeeded to old growth.  Elk were re-introduced here in 2001, but they inhabit a small area of the park difficult to access.  The road leading to this spot is a dangerous single lane dirt path on the side of a mountain.  Supposedly, the black bear population in the park is about 1600.  During the summer black cherries (Prunus serotina) make up 25% of the bear’s diet.  Garbage provides 8% of their diet here.  The author of the below referenced monograph claims to have several photographs of cougars taken by park visitors circa 2003.  These may be of captive cougars released by owners who no longer wanted to care for them.  Cougars are normally secretive, and semi-tame cats may have been easier to photograph.  I doubt there is a breeding population of cougars in the park, but I wouldn’t rule it out, and they may eventually recolonize the region, if they keep expanding their range from the west and south Florida.

Location of the Great Smoky Mountains Park.  The diversity of megafauna species in this park is much lower now than it was in this region during the Pleistocene.

Strange as it may seem, wild black cherries make up to 25% of the black bear’s diet during mid to late summer in the Great Smoky Mountains National Park.

The below referenced monograph reports a population of 30 striped skunks inhabit the Cades Cove Campground of the Great Smoky Mountains National Park.  They den in drainage culverts.  Avoid them or you will endure a stinky vacation.

A fluctuating population of endangered Indiana bats roosts in a cave in Cades Cove.  Bats can be seen at dusk.

The variety and abundance of megafauna in the Great Smoky Mountains National Park is disappointing, but it was spectacular during the Pleistocene.  The natural communities then were similar to those of today, but during cold glacials there probably were more spruce trees and grassy balds and in higher elevations there may have even been tundra-like environments.  Here’s a list of large mammals (based on fossil evidence) that definitely inhabited the park region until ~11,000 BP or beyond.

Jefferson’s ground sloth

Harlan’s ground sloth

tapir

horse

half-ass

mastodon

long-nosed peccary

flat-headed peccary

stout-legged llama

helmeted musk-ox

bison

white-tailed deer

caribou

elk (probably not until 15,000 years BP)

giant beaver

black bear

Florida spectacled bear

giant short-faced bear

cougar

jaguar

saber-toothed cat

scimitar-toothed cat

coyote

dire wolf

Here’s a list of additional megafauna species that likely inhabited the park but whose nearest fossil remains are a considerable distance away.

pampathere

stag-moose

Columbian mammoth

woolly mammoth

Columbian mammoth x woolly mammoth hybrids

gompothere (during warm climate cycles)

giant lion

dhole

The Pleistocene Great Smoky Mountains hosted ~31 megafauna species compared to the present day total of 5.  This is a >80% reduction.  How sad.

Reference:

Linzey, Donald

“Mammals of the Great Smoky Mountains National Park: 2016 Revision”

Southeastern Naturalist 15 Monograph (8) 2016

 

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Pleistocene Skunks

The skunk’s black and white markings warn predators, even those lacking color vision, to beware of the noxious spray this animal is capable of unleashing.  The skunk’s defense mechanism is so effective they seem to fear no other animal.  When threatened they often run toward much larger animals and chase them away.  Nevertheless, skunks do suffer predation.  Most notably, great horned owls (Bubo virginianus) specialize in taking skunks, and the owls seem to be immune to the spray.  For this reason some great horned owls smell like skunk.  Cougars stalk and kill skunks before the skunk has time to respond.  Formerly, some Native Americans preferred skunk to other types of meat such as turkey.

Scientists no longer consider skunks to be members of the weasel family, the mustelidae.  Instead, skunks and old world stink badgers belong to a family all their own known as the mephitidae.  Today, Georgia is h0me to 2 species of skunks–the striped (Mephitis mephitis) and the spotted (Spilogale putorious).  During the Pleistocene hog-nosed skunks (Conepatus leuconotus) lived throughout the south as well, leaving fossils at Ladds Mountain, Bartow County, Georgia and several sites in Florida.  The extinct short-faced skunk (Brachyprotoma obtusata)  may have extended its range into the upper south but was more of a boreal species.  Fossils of this species have been found as far south as Arkansas.

Striped skunk–the most common species found in Georgia today and probably during the Pleistocene.

Striped skunks are the most common skunk in Georgia today, and are the only species found in more than 1 fossil site in state, so they likely were the most common species throughout the Pleistocene.  Striped skunks are omnivorous, feeding on small mammals, reptiles, birds, insects, and fruit.  I’ve never seen a live individual, but I have frequently seen road-killed skunks in rural areas of north Georgia.  They prefer broken country with a mix of fields and woods.  Curiously, they’re rare near Augusta, Georgia, perhaps because there aren’t many farms with stores of grain that attract enough mice to entice skunks.

Spotted skunk.  When a spotted skunk displays a handstand flee the scene immediately…it’s about to spray.

I did see a live spotted skunk once in 1990, while I was throwing a paper route at about 5:00 am on Sand Bar Ferry Road located east of downtown Augusta.  Spotted skunks are attractive little animals that climb trees–an unusual behavior for a skunk.  Spotted skunks prefer forest edge and prairie habitats and are common in the middle part of North America but less abundant on the edges.

Hog-nosed skunk.  Note the claws for digging up grubs.

Current range of hog-nosed skunk and closely related South American species.  During the Ice Age its range expanded into the southeast of North America because there was more brushy arid habitat then.

Hog-nosed skunks prefer arid brush and grassland habitats, thus explaining why they occupied the south during the Ice Age but no longer occur here.  Arid scrub habitat expanded across the southeast during the Ice Age because the climate was drier then.  Like striped and spotted skunks, hog-nosed skunks are omnivorous but rely more on insects for a greater part of their diet than other skunk species.

Little is known about the extinct short-faced skunk.  It was a small skunk, more like the spotted skunk than any other extant species.  Based on its fossil distribution, it was an animal of the boreal forests that predominated south of the ice sheet.  It co-existed with the other 3 species of skunks, but unlike them, it failed to adapt to the environmental changes that occurred ~8,000 years BP.  Perhaps, they were more vulnerable to diseases carried by an increased population of parasites in the warming climate.

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.