Peccary Cave in Arkansas

Perhaps the best site for Pleistocene fossils in Arkansas is Peccary Cave located in Newton County.  The site was first excavated in 1960s, and a follow-up expedition prospected for fossils again in the early 1990s.  The fossil remains of at least 51 species of mammals have been found here. 4000 specimens of a minimum of 64 individual flat-headed peccaries (Platygonus compressus) were discovered in the cave, hence the name.  The bones of other extinct species excavated from the cave include mammoth, mastodon, bison (Bison antiquus), stag-moose, helmeted musk-ox, tapir, beautiful armadillo, and dire wolf.  There are also remains of extralimital species found here that no longer occur in the region–grizzly bear, pine marten, porcupine, heather vole, and numerous other rodents and insectivores of northern affinities.  Plenty of species still found in the region are represented in the cave as well such as beaver, otter, muskrat, raccoon, coyote, gray fox, opossum, and either mule or white-tailed deer. Reptile and amphibian specimens have been excavated from the cave along with a few human-made artifacts of unknown cultural origin.

Newton County, location of Peccary Cave.  

Illustration of the flat-headed peccary.  Peccaries didn’t use Peccary Cave as a den.  Instead, they either fell inside or their bones were washed into the cave when the nearby creek flooded.  Birds of prey dropped or defecated smaller animals into the cave from overhanging trees.

The fossils represent several different climate phases.  The lowest level contains fossils over 22,000 calendar years BP, a climate phase that includes a weak interstadial and the following early glacial maximum.  Mixed Ice Age woodlands of spruce, pine, and hardwoods interspersed with prairies predominated.  7 different species of squirrels lived in the region then, showing how many diverse habitats occurred here.  Red squirrels and least chipmunks, now absent from the region, preferred spruce forests; gray squirrels, fox squirrels, and southern flying squirrels occur in temperate hardwood forests; woodchucks like meadows; and 13-lined ground squirrels require tree-less plains.  The author of the study discussed below thinks the following glacial maximum caused the entire Missouri Plateau to become inhospitable desert because there are few fossils from the site, dating to between 21,000 calendar years ago-15,000 calendar years BP.  Undoubtedly, the region became more arid during this climate phase, and desert scrub grassland likely predominated, but I think there are alternative explanations for the lack of fossils during this time period here: a) the cave entrance may have become closed and/or b) the barren landscape allowed animals to see the trap entrance and avoid it whereas before it was hidden by thick vegetation and animals frequently fell inside.  Without overhanging limbs there was no perch for birds of prey to drop of defecate the remains of their meals.  Moreover, the nearby creek dried up, so there were no floods to wash fossils into the cave.

The upper level of sediment represents a warm dry interstadial post 15,000 calendar years BP when the region was dominated by grassland.  Bison fossils appear during this phase, and toad fossils outnumber frog bones.  Toads can survive better than frogs in more arid climates.

Kurt Wilson wrote his PHD thesis about the peccary and dire wolf bones found in Peccary Cave.  His paper has interesting information, but it is incompletely researched, and his conclusions are logically flawed.  He believes flat-headed peccaries were always an uncommon species.  Part of his reason for this assertion is based on his incorrect observation that “the southeast is virtually devoid of records (of flat-headed peccaries), except for a dozen localities in Florida.”  Wilson is unaware of 2 sites in north Georgia (Yarbrough Cave and Ladds) and 1 site in coastal South Carolina where fossil remains of flat-headed peccaries have been found.  It is also illogical to assume a species was absent from a region based on its absence in the fossil record.  Large areas of the southeast are devoid of fossils because the local geology is not conducive to fossil preservation, not because animals didn’t live there in the past.

Wilson concludes flat-headed peccaries became extinct due to climate change based on 4 lines of evidence that are easily debunked.

1. He dismisses overhunting by humans as a cause of flat-headed peccary extinction when he regurgitates the tired old claim of Meltzer and Grayson (an archaeologist and anthropologist…not paleoecologists) that there isn’t enough archaeological evidence of human interaction (kill sites) with this species.  I consider this reasoning absurd in the extreme.  99.999…etc% of animals that ever lived on earth left no fossil evidence whatsoever.  It has always seemed unreasonable to me to expect the remains of the final populations of a species that overlapped with man for less than 2000 years to be preserved in the fossil record.  The chances of this happening are tiny.  I’ve noticed Grayson’s recent book published in 2016 is frequently being cited in new papers about Pleistocene vertebrates.  Grayson was blatantly dishonest in this book in the way he characterized a study that rules out climate change models of extinction.  (See: https://markgelbart.wordpress.com/2017/01/23/donald-graysons-disingenous-case-against-overkill/ ) Grayson lied and he knows he lied.

2. Wilson assumes flat-headed peccaries became extinct in this region about 22,000 calendar years BP because their remains don’t occur in cave sediment after this date.  (When Wilson writes of extinction in his paper he means regional disappearance or extirpation because he’s aware terminal dates for this species in other regions are 11,000 calendar years ago.  Nevertheless, he clumsily never makes this distinction in his paper.)  He asserts peccaries became extinct here because the climate became too arid for them.  Again, he is basing his assertion on the dubious assumption that the absence of evidence is evidence of absence.  I think flat-headed peccaries were probably even more abundant during the arid climate phase because they were anatomically well-adapted to dry dusty environments.  Flat-headed peccaries had extensive structures in their nasal passages that helped filter dust.  Wilson must be unaware there are at least 9 fossil sites where herds of flat-headed peccaries were buried during sandstorms.  (See: https://markgelbart.wordpress.com/2013/03/10/when-sand-dunes-buried-herds-of-flat-headed-peccaries/ ) This suggests they were common in desert environments.  Flat-headed peccaries may have avoided falling in Peccary Cave after 22,000 calendar years BP because the area around the entrance to the cave was barren and not hidden by vegetation.  None happened to fall in the cave after this date, but that doesn’t mean they didn’t still occur in the region.  Other fossil sites in the region yield the remains of horses, but not a single horse fossil has been found in Peccary Cave.  Horses were likely another abundant species in the region that just happened to never fall in or enter Peccary Cave.

3. Wilson did a stable isotope analysis of 2 flat-headed peccary teeth and concluded they fed upon just a few leguminous plant species, so they became extinct when these limited number of plant species disappeared from the region.  I don’t believe the entire dietary breadth of a species can be determined from such a small sample size.  Moreover, 1 study suggests stable isotope analysis is not at all reliable.  (See: https://markgelbart.wordpress.com/2016/06/24/trust-the-coprolites-not-the-stable-isotope-analysis/ )  Scientists compared the results of a stable isotope analysis of moa bones with actual fossil droppings.  The stable isotope analysis was wrong.  Flat-headed peccary teeth were built to eat grass and tough vegetation.  A species that survived millions of years of climate change didn’t exclusively feed upon just a few species of leguminous plants.

4. Wilson asserts flat-headed peccaries were uncommon and thus vulnerable to extinction.  However, a new genetic study of 12 flat-headed peccary individuals from Sheridan Cave, Ohio, dating to just before their extinction revealed populations of this species were diverse and expanding.  This suggests flat-headed peccaries were common, adaptable, and had a wide geographical distribution until the species’ demise.

Peccary Cave has yielded a wealth of information for paleoecologists, and I’m shocked at how little research has been published about this site.  I’ve been able to find about half a dozen research papers.  There hasn’t been a scientific excavation of the site since 1993, though amateurs are currently pillaging it.  Most of the specimens from this site have not yet been described in the scientific literature, and they are not listed on the paleobiology database. An early report of the site mentions the existence of peccary “droppings.”  Yet, nobody has studied the coprolites (please email me if I’m wrong)–an outrageous oversight.  We could actually find out what flat-headed peccaries ate, instead of guessing based on stable isotope analysis.  I’m not sure the coprolites were even collected and stored in a museum.  There should be hundreds of published papers about this site, not just a paltry 6.  I’ve come across other understudied fossil sites and collections in my research, but this site might possible be the most underappreciated.

References:

Bell, Kenneth; and Lee Davis

“Sinkhole Excavations in Peccary Cave, Newton County, Arkansas”

Arkansas Academy of Science 47(30) 1993

Davis, Lee

“Biostratigraphy of Peccary Cave, Newton, County, Arkansas”

Arkansas Academy of Science 1969

Perry, Tahlia; et. al.

“Ancient DNA Analysis of the Extinct North American Flat-headed Peccary (Platygonus compressus)”

Molecular Phylogenetics and Evolution 2017

Wilson, Kurt

“Late Pleistocene Extinction of the Flat-headed Peccary on the Ozark Plateau: Paleozoological Insights from Peccary Cave”

Iowa State Graduate Thesis 2017

 

 

 

The Sheridan Cave Pit Fossil Site in Wyandot County, Ohio

The owner of the Indian Trail Caverns tourist site in Wyandot County, Ohio decided to dig through a shallow depression near the cave where on weekends he allows people to visit for a few dollars admission.  He hoped to find a passage that led to his cave.  Instead, his digging uncovered a former sinkhole trap that had developed when rainwater dissolved through Paleozoic-aged limestone bedrock during the late Pleistocene.  The sinkhole cave had since filled with sediment, but his excavation uncovered the bones of the Pleistocene-aged animals that had fallen into the cave.  Gregory Macdonald of Cincinnati University took over and supervised the excavation from 1990-1995.  After human artifacts were found, Ken Tankersley, an archeologist, became the excavator-in-chief.

Location of Wyandot County, Ohio.

The most common fossils in the cave were those of flat-headed peccaries, an extinct species well adapted to living in arid, sandy grasslands.  They lived in herds.  At least 43 individuals became trapped in the cave.  By contrast, only 1 long-nosed peccary, an animal that likely preferred forest edge, fell in the sinkhole.  Fossils of other ungulate species found in the sinkhole include the extinct stag-moose (Cervalces scotti), caribou, and white tail deer.  Two species of bear died in the cave–the extinct giant short-faced bear (Arctodus simus) and a black bear.  Fossils of some of the species of smaller animals that lived here at the end of the Ice Age were from species that no longer occur this far south: pygmy shrews, yellow-cheeked voles, heather voles, pine martens, and fishers, though the latter may have survived here till the time of European colonization.  Red squirrels prefer boreal forests and used to range here as well but presently do not.  The extant species of beaver and the extinct giant beaver (Casteroides ohioensis) lived in this area then.  Raccoons, striped skunks, weasels, woodchucks, chipmunks, gray squirrels, porcupines, and rabbits are part of the present day fauna that also lived here during the late Pleistocene.  Bones of turkey, channel catfish, and bullheads were probably brought into the cave by avian predators.  As I noted in an essay last week, I hypothesize bullhead catfish were the most common fish living in southeastern North America during the coldest phases of the Ice Age, and that may have been true in the midwest too.

This bone spear point was found in the sinkhole next to this flat-headed peccary shoulder blade with a hole in it that matches the spear.  This is direct evidence that man did hunt peccaries during the Pleistocene–a fact that some archaeologists bizarrely dispute.  They dispute it because they want to deny that man is responsible for megafauna extinctions.  How much evidence do they need?

Flat-headed peccary bones found in-situ in the sinkhole.

Paleontologists have yet to find the fossils of mammoths, mastodons, horses, bison, elk, helmeted musk-ox, wooly musk-ox, Jefferson’s ground sloth, scimitar-toothed cats (Dinobastis serum),  grizzly bears, or snowshoe hares at this site, but these species have been found in other sites in the region and likely occurred in this area but none happened to fall inside the pit.  I don’t think saber-tooths (Smilodon fatalis) nor dire wolves ranged this far north.  Scimitar-tooths and timber wolves occupied their ecological niches in this region.

Several human artifacts were discovered by paleontologists searching through the vertebrate fossils.  A stone arrowhead and scraper were identified as being from a late Clovis culture.  Two bone spearpoints were also found, and a hole found in a fossil peccary shoulder blade perfectly matches the spearpoints.  One of the points appears as if it had impact damage from striking the bone.  Some of the fossil bones are burned–either by humans or in a forest fire.  Remains of a butchered snapping turtle suggest humans enjoyed a chelonian snack at this site.

Radio-carbon dating of charcoal indicates calender year dates of 12,600 BP-13,000 BP.  Burned bones give ages about 1000 years older than that.

The site of the Sheridan sinkhole trap was under the southern lobe of the Laurentide Ice Sheet during the Last Glacial Maximum.  The sinkhole likely formed following the withdrawal of the glacier when an increase in precipitation facilitated the collapse of the underlying limestone bedrock.  The region was mostly bare rock, gravel, and loess (rock ground to dust by glacier movement) for a few centuries; and because it was located at the edge of a receding glacier, conditions were windy.  The first species of plants to colonize this area were the lichens that could grow on the rocks.  Pioneer stands of cedar, aspen, and ash soon took root in the shade-free environment.  Thickets of some unknown thorny shrub species probably spouted, providing protection for the herds of flat-headed peccaries, a species capable of enduring the frequent sandstorms stirred by the winds blowing off the nearby glacier.  Caribou also survived here, able to eat lichens.  After a thousand years or so, grass, spruce, jack and red pines, and even oak colonized the area around the site, creating some forest edge habitat and attracting red squirrels, rabbits, white tail deer, and long-nosed peccary.  The cool moist conditions and an abundance of glacial meltwater created bogs and marshes–habitat for beavers, giant beavers, and possibly the  stag-moose, if the latter had the same habitat preferences as the extant species of moose.  (The stag-moose, despite its name, was not closely related to the modern day moose.)  For a few thousand years, boreal forest elements mixed with deciduous flora and fauna, making for an odd environment for which there is no modern analogue.  Eventually, as the climate warmed, broadleaf trees became dominant in this region, and sediment filled the sinkhole so that it no longer acted as a trap…and a window to the ecology of the past.

References:

Hansen, Michael

“Indian Trail Cavern–A Window of Ohio’s Pleistocene Past”

Ohio Geology Spring 1992

Haynes, Gary

The Early Settlement of North America

Cambridge University Press 2002

http://www.lithiccastinglab.com/gallery-pages/2001octobersheridencavepage1.htm

When Ice Age Georgia Became Desert-like

During the Last Glacial Maximum when much of the world’s water became locked in glacial ice sheets, the climate in southeastern North America was much drier.  Small rivers dried up and larger rivers shrank in size and became braided in pattern so that they were like long chains of disconnected channels.  The exposed river sands blew into eolian dunes like those from this picture of a modern Mojave desert dune.  Ironically, during these cold stadials, as the climate became dry in southeastern North America, precipitation increased in the southwest, so that it was quite lush there.  

Dry climate phases have periodically struck southeastern North America many times over the past 5 million years.  Scientists know little about the paleoecological details of most of these phases because there’s not much available data.  But thanks to one study, they do have a relatively clear understanding of the ecological composition of south central Georgia from 30,000 years BP-25,000 years BP.

Scientists took a 17 foot core of sediment from a peat deposit next to Sandy Run Creek on Warner Robins Air Force Base which is located near Macon, Georgia.  They radio-carbon dated the sample and counted the pollen grains to determine what the environment was like during this time period.  This was a time of glacial expansion and as much of the earth’s water became locked in ice, less moisture in the atmosphere was available as precipitation.  Southeastern North America experienced extended droughts causing the water table to drop.  Water flow on major rivers was greatly reduced creating braided river patterns and this turned the rivers into chains of disconnected channels interspersed with islands and sandbars.  In some cases small rivers completely dried up, exposing great quantities of river borne sand.  Atmospheric conditions caused by the glacier to the north spawned frequent westerly and southwesterly winds that blew this river borne sand across the landscape forming huge eolian sand dunes.

Today, vegetation has taken root and holds down the eolian sand dunes that formerly rolled across Georgia’s landscape during cold arid stadials.  Now, scrub turkey oak and longleaf pine covers the Ohoopee sand dune in Georgia.  The sandy soil is of poor quality and not enough litter accumulates to foster fire, allowing scrub oak to become more common than pine. Photo is from google images.

Photo from google images of the Ohoopee River.  This and other small rivers dried out during cold dry climate phases.  Instead, small pools of water appeared sporadically in the river bed.  The scene would have resembled modern African water holes.

The evidence from the pollen composition of the Sandy Run Creek peat core indicates a much different landscape than occurs anywhere in Georgia today.  While eolian sand dunes rolled to the east of reduced or even completely dried rivers, lightly wooded grasslands predominated over much of the environment.  Here and there were groves of pine with some spruce.  (The species of pine isn’t known, but my educated guess is they were a mixture of northern and southern species, probably shortleaf and white.  The species of spruce was likely the extinct Critchfield’s.) Oaks and other deciduous trees clung to the vicinity of shrinking water holes found along the braided rivers.  Pine composed 39%-75% of the pollen, while oak only made up 12%. Grass and coniferous trees require less water than hardwoods, and are less prone to physical damage from frequent wind, explaining why they were more abundant.  Scientists found no charcoal in the part of the core dating from 30,000 BP-25,500 BP–evidence wild fires were a rarity.  This suggests a thinly vegetated environment where combustible material such as dead wood didn’t accumulate.  Moreover, lightning storms that ignite fires were uncommon.  Charcoal is present in the part of the core dating from 25,500 BP- 25,000 BP, perhaps indicating a weak interstadial with more frequent electrical storms.

Grass-eaters such as mammoths, horses, and bison likely predominated in this kind of environment along with the occasional Harlan’s ground sloth which preferred more open environments than its cousin–Jefferson’s ground sloth.  Badgers, thirteen-lined ground squirrels, and perhaps jackrabbits colonized the region then.  Animals that prefered more forested environments were restricted to riverine woods.  Game accumulated around shrinking water holes and this probably contributed to erosion of riverbanks which in turn added sediment to the formation of eolian dunes.  These congregations of herbivores attracted predators such as dire wolves, jaguars, and saber-tooths.

You can buy this illustration of flat-headed peccaries (Platygonus compressus) from the website engraved on the image.  This kind 0f peccary was probably pretty common during dry climate phases in the south.  They ate tough spiny vegetation such as cactuses.  They lived in large herds that were probably aggressively defensive, much like modern white-lipped peccaries.

Photo of a jaguar in Arizona.  Jaguars inhabit many different types of environments such as deserts and rain forests.  They were adaptable enough to probably have been the most common large cat in southeastern North America during stadials and interstadials.

Photo of a hog-nosed skunk.  Today, this species lives in Mexico and the southwestern United States.  Fossils of hog-nosed skunks have been found in Georgia and Florida.  They must have colonized the region during dry climatic phases.

There’s no sediment in the Sandy Run Creek peat core dating from 25,000 BP-13,000 BP.  Scientists call this an erosional unconformity.  They believe the creek changed coarse or flooded and washed away all the sediment accumulated during this time period.  This is consistent with what we know of the environmental changes that occurred during this time period.  About 16,000 years BP the Boling-Alerod interstadial began.  The Laurentide Glacier rapidly commenced melting, putting more moisture in the atmosphere and precipitation increased.  The water table rose and so did river flow.  Rivers no longer consisted of braided patterns, but instead meandered to an even greater degree than they do today, forming scroll-like sandbars.

Satellite view of a meandering river with scroll bars.  During the Boling-Alerod Interstadial beginning about 16,000 years ago, precipitation increased, causing rivers to meander even more than they do today.  This new river pattern formed frequent scroll bars. a kind of sand bar created when the meander of a river continously shifts and leaves ridges parallel to the meander.

Though sand dunes no longer rolled across the landscape during the interstadial, there’s evidence of considerable sandbar formation.  Scroll bar formation suggests a dry season/wet season climate.  Autumn and early winter were mostly dry and river levels fell, exposing sand bars.  But existing atmospheric factors caused heavy precipitation in late winter, spring, and early summer.  Warm tropical fronts collided with cold parabolic winds originating from the still extant glacier.  This spawned great snow, ice, and rain storms that caused massive floods.  Rivers shifted.  Occasional tropical storms compounded this trend.

The pollen record of the Sandy Run Creek peat core, which picks up again about 13,000 BP, demonstrates a much different environment from that of 25,000 BP.  From 13,000 BP-11,000 BP there was a sudden cooling trend known as the Younger Dryas.  The paleobotanical evidence, however, still shows the influence of the previous interstadial warming trend.  A cool, moist, open oak woodland prevailed in south central Georgia during this time period.  Oak pollen doubled from 12% to 24% while pine pollen declined to just 7%.  Critchfield’s spruce and fir were still present but so were hickory and beech–a clue that temperatures were moderate but remained cooler than those of today.  An increase in charcoal is evidence that vegetation was thicker than it had been in the previous time period because now there was more forest litter available as tinder for fires.  And the frequency of lightning storms, which ignites fires, increased.  A northern species of alder, a type of shrubby birch that no longer occurs in Georgia, commonly grew in abandoned, dry, river meanders.  Grasslands still existed to a greater extent than occurs naturally today but had declined in abundance compared with 25,000 years BP.

Scientists use an interesting method to help determine changes in the density of vegetation over time.  They add exotic pollen to cores of sediment.  In this study of the Sandy Run Creek sediment core, they added a known quantity of eucalyptus–a species which didn’t live in North America during the Pleistocene.  The ratio of eucalyptus to native pollen was high during the time period of 30,000 years BP-25,000 years BP–evidence vegetation density was low.  Conversely, the ratio of introduced eucalyptus pollen was low during the time period between 13,000 years BP-11,000 years BP–evidence the vegetation density was higher.

The change to a more moist wooded environment favored higher populations of mastodon, deer, long-nosed peccary, bears, beavers, tree squirrels, and cottontails.

References:

Lamoreaux, Heidi; George Brook, and John Knox

“Late Pleistocene and Holocene Environments of the Southeastern U.S. from the Stratigraphy and Pollen Content of a Peat Deposit on the Georgia Coastal Plain”

Paleogeography, Paleolimnology, and Paleoecology 2009

Leigh, David

“Late Quaternary Climates and River Channels of the Atlantic Coastal Plain, Southeastern USA”

Geomorphology 2008