Extensive Late Pleistocene to Mid-Holocene Wetlands along the Tennessee River

A paper about extinct giant beaver (Casteroides sp.) fossil remains in the mid south briefly mentions evidence for the existence of “extensive floodplain lakes and marshes along the middle stretch of the Tennessee River” during the late Pleistocene-mid Holocene.  This intrigues me. Following the end of the Ice Age, increased precipitation in the atmosphere from melting glaciers caused southeastern rivers to meander more than they do today.  Geologists actually refer to these river patterns as supermeanders, and supermeandering rivers were common between ~15,000 BP-~6,000 BP.  Meanders often get cut off from the main river channel, and they become oxbow lakes, a name that describes their curved shape.  Sediment eventually fills oxbow lakes, and during this process they become marshy.  Large oxbow lakes created by this period of supermeanders attracted huge flocks of wintering waterfowl.  Archaeologists found enormous quantities of mallard duck (Anas platyrhyncos) remains dating to the late Pleistocene-early Holocene in Dust Cave and Smith-Bottom Cave, both located in northwestern Alabama.  The ducks were brought inside the caves by early archaic Indians who enjoyed a steady diet of duck during the winter.  70% of the faunal remains in Dust Cave were birds, mostly waterfowl but also including passenger pigeon, bobwhite quail, and prairie chicken.

Diagram showing how oxbow lakes are formed.  There must have been huge oxbow lakes along the Tennessee River during the supermeandering phase of ~15,000 BP-~6,000 BP

Map of Tennessee River.  Abundant remains of ducks and other waterfowl in caves near the river suggest a very extensive wetland occurred along the middle stretch of the river during the Late Pleistocene-to mid Holocene.

Caves are located  on both sides of the Tennessee River in northwestern Alabama.  They preserve evidence that early Indians ate a lot of duck.

Huge flocks of mallard ducks wintered on oxbow lakes and marshes along the Tennessee River during the late Pleistocene-mid Holocene.

Dust Cave was buried by sediment until ~15,000 BP when the nearby Tennessee River changed coarse and eroded through this sediment, exposing the cave entrance.  Indians occupied the cave from ~12,500 BP-5000 BP.  Archaeological evidence shows 5 succeeding cultures utilized the cave. The Indians buried their dead in Dust Cave and left plenty of archaeological evidence such as arrowheads and the impressions of textile weaving on clay.  Toward the end of this time, Indians utilized waterfowl less than their predecessors had and relied more on upland game.  This suggests wetlands and lakes in the region eventually were diminished in extent.

During the time of supermeanders swamp rabbits (Sylvilagus aquaticus) were common.  Flooding helped establish extensive stands of impenetrable bamboo cane (Arundinaria gigantea) known as canebrakes, a favored habitat of swamp rabbits.   Floods killed trees and deposited rich soil.  Bamboo cane thrives on open sunlit ground with well fertilized soil.

Swamp rabbits were abundant here as well.

The deepest lakes offered habitat for the freshwater drum (Aplodonitis grunniens).  This species prefers clear water with sandy or gravel bottoms.  They feed on mussels, insect larva, and small fish.  Freshwater drums, suckerfish, and catfish made up 8% of the faunal remains in Dust Cave.  Fish was an important summer food for Archaic Indians after ducks migrated north.

Indians ate freshwater drum.

The extinct giant beaver occupied the oxbow lakes and marshes created by the supermeandering patterns of the Tennessee River until Indians hunted them to extinction.  (A safe assumption, though no direct evidence of humans hunting giant beavers has ever been found.)  Perhaps, they even persisted here early in the Holocene because the habitat they favored was so extensive.  Remains of giant beavers have been found at 3 sites along the Tennessee River including Ruby Falls, Bell Cave, and ACb-3 Cave.  The latter 2 sites are located in Colbert County, Alabama.  There were at least 2 species of giant beaver–Casteroides ohioensis and Casteroides dilophidus.  C. ohioensis lived in the Midwest; C. dilophidus lived in Florida and south Georgia.  Scientists aren’t sure which species lived along the Tennessee River because not enough skeletal material was found to distinguish between species.  Giant beavers preferred the same habitat as the modern day muskrat (Onadatra zibethicus) and did not require wooded environments like extant modern beavers (Castor canadensis).

Giant beavers (Casteroides sp.) lived in these wetlands until the Indians overhunted them to extinction.

References:

Parmalee, Paul; and Russell Graham

“Additional Records of the Giant Beaver, Casteroides, from the Mid South: Alabama, Tennessee, and South Carolina”

Tributes to the Career of Clayton Ray, Smithsonian Series of Publications 2002

Pritchard, Erin

TVA Archaeology: 75 Years of Prehistoric Site Records

University of Tennessee Press

 

 

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Canebrakes are Forlorn Landscapes

200 years ago, landscapes in southeastern North America looked nothing like they do now.  When William Bartram traveled through the piedmont region of the south (circa 1775), the path he followed mostly stayed on the high ground because impenetrable thickets of bamboo cane (Arundinerea gigantea) grew alongside creeks and river bottoms.  His party was always in sight of canebrakes as they traveled through the open woodlands on the high ground.  Canebrakes covered tracts that were hundreds of square miles in extent.  Today, canebrakes are nearly an extinct type of environment.

I looked for this photo on google images and couldn’t find it.  I did find it within a pdf document but I couldn’t link the photo directly. So I scanned it from the book Forgotten Grasslands of the South by Reed Noss.  Click to enlarge.  It’s of a man on a horseback dwarfed by a stand of 40 foot tall cane in 1906.  This was probably one of the last stands of a primeval canebrake.

I found this stand of bamboo cane growing behind a Burger King in Madison, Georgia.  Cane is planted as an ornamental.  It’s probably not even American bamboo, but rather Asian bamboo.

Canebrakes are an ancient environment, dating back to at least the Miocene (25 million-5 million years BP).  It’s a species of grass.  Grasses began to become abundant during the Oligocene (33 million-25 million years BP).  Scientists unearthed ~5 million year old fossil bamboo from the Gray Fossil Site in Tennessee along with the bones of an extinct species of red panda (Pristinailurus bristoli) that fed upon it.  American bamboo likely shares an ancestry with Asian bamboo back when both continents were composed of a continous mosaic of tropical environments.  ( https://markgelbart.wordpress.com/2012/12/05/the-gray-fossil-site-in-washington-county-tennessee/)  Scientists disagree over whether giant gane (Arundinerea gigantea) is the same species as switch cane  (A. tecta).  Some botanists argue a structure inside switch cane makes it a different species, but others don’t think the difference is significant enough.  In any case cane grew in dense stands on rich soils, either by itself in pure stands or with an occasional tree in a savannah-like landscape.  Cane is shade intolerant and today seems to be restricted to wooded swamp edges.

Canebrakes require a complicated combination of forcing events to exist.  Formerly, floods, flocks of passenger pigeons, windstorms, or ice storms destroyed great tracts of forest.  Passenger pigeons (Ectopistes migratorius) used to roost in flocks estimated to be in the billions.  Witnesses described their roosting areas as resembling tornado damage.  Great limbs and even whole trees broke in half under the weight of the birds, and the pigeon dung killed the trees via overfertilization.  (See also https://markgelbart.wordpress.com/2010/08/27/pleistocene-passenger-pigeon-populations/) The New Madrid earthquakes in 1811 also caused the creation of large tracts of canebrakes.  Following these natural disturbances of the forest, a great amount of flammable dead wood covered the forest floor.  Lightning or human set fires burned through the woody refuse, creating vast sunny areas that allowed shade-intolerant bamboo cane to colonize large tracts of land.  Cane growing in small sunny patches within the forest could take advantage of these disturbances by spreading clonally from root rhizomes into the newly suitable habitat.  As long as fire occurred at least once a decade, canebrakes could be maintained indefinitely.  Dr. Noss suggests canebrakes were an alternate climax stage with bottomland forests near rivers and streams.  Without disturbances these areas succeeded to bottomland forests, but disturbances were so common that canebrakes may have covered an equal amount of territory.

Modern studies show that fire and windstorm double the growth of cane which can grow as fast as 20 feet annually.  Cane formerly reached heights of 40 feet, perhaps because they were enriched with pigeon dung.  Today, the tallest cane known grows in Louisiana and reaches just 30 feet in height.  It depends mostly on clonal growth and only flowers and produces seed once every 40-50 years.  It prefers rich river bottomland soils where it can become dominant.  Surprisingly, rich soils have less species diversity than poor soils.  On poor soils no one species can become dominant due to more difficult growing conditions.

Canebrakes were undoubtedly a widespread environment during the Pleistocene before man colonized North America.  There are many endemic species of animals that depend exclusively upon canebrake habitats, and it’s unlikely they evolved that dependence within the last 15,000 years.  However, canebrakes likely enjoyed a heyday during the 18th century when Native American populations collapsed.  Indians preferred to grow their crops on rich river bottomland soils and when they abandoned their fields cane rapidly colonized the land.

Modern anthropogenic changes in land use have nearly eliminated canebrakes.  Humans built levees and dams to prevent flooding.  People suppress fires.  People exterminated passenger pigeons.  These activities ended ancient patterns of disturbances that bamboo cane requires to form vast monotypical stands.  Moreover, cane grew on rich soils that farmers coveted for field crops, and the farmers let their livestock overgraze cane growing on any land left unplanted.  Today, river bottomlands left undeveloped are dominated by trees that shade out cane.  Canebrakes are a forlorn landscape and will be difficult to re-establish.

Canebrakes were a rich habitat utilized by many species of animals.  Cane is a high quality forage that formerly provided food for grazers such as mammoths, horses, and bison.  Bears and big cats liked to den inside the thickets where they could hide their cubs.  Swamp rabbits (Sylvilagus aquaticus) are also known as canecutters because they feed upon cane by gnawing through the stem to fell the tall grass so they can get at the leaves.  If it’s not extinct, Bachman’s warbler (Vermivora bachmanii) and Swainson’s warbler (Limnothlypis swainsonii) depend upon canebrake habitat.  Eastern diamondback rattlesnakes (Crotalus adamteus), also known as canebrake rattlesnakes, hunt swamp rabbits in the thickets.  6 species of butterfly depend entirely upon bamboo cane as part of their life history.

Swamp rabbits are also called canecutters.  They’re much larger than cottontails.

Bachman’s warbler.  This bird is probably extinct.  They formerly summered in canebrakes.  They built their nests in the cane thickets and foraged for insects on the ground in the fallen cane leaves.  They wintered in Cuba.  They became extinct (probably) because canebrakes are gone.  None have been seen since 1988.

A man holding an eastern diamondback rattlesnake.  They are big serpents growing to 8 feet long and weighing 35 pounds.

Southern pearly eye (Enodia portlandia).  5 other species of butterfly depend upon canebrakes for at least part of their life cycle including Creole pearly eye (E. creota), southern swamp skipper (Poanes yehl), cobweb little skipper (Amblyscertes aesolypia), cane little skipper (A.reversa), and yellow little skipper (A. carolina).  These endemic species are evidence canebrakes predate anthropogenic influences on the environment.

Native Americans also used to rely on bamboo cane.  They used to mix mud with strips of cane to build houses, and they covered the floors inside with mats made of cane.  They made baskets and fish traps and coffins from cane.  Weapons fashioned out of bamboo cane included spears, knives, body armor, and blowguns.  Indians incorporated cane into the structures of their famous mounds.  Cane even provided food.  Bamboo shoots are a tasty vegetable, and the seeds could be ground into a flour that was reputed to be almost as good as wheat flour.

References:

Ellsworth, J.W.; and B.C. McComb

“Potential Effects of Passenger Pigeon Flocks on the Structure and Composition of Presettlement Forests of Eastern North America”

Conservation Biology 17: 1548-1558 2003

Gagnon, P.R.; and W.J Platt

“Multiple disturbances accelerate clonal growth in potentially monodominant bamboo”

Ecology 89: 612-618 2008

Platt, W.J.; and C.J. Brantley

“Canebrakes: An Ecological and Historical Perspective”

Castanea 62: 8-21 1997

Rabbits will Inherit the Earth

Matthew 5:5 (“Blessed are the meek for they shall inherit the earth”) always reminds me of rabbits for these meek creatures surely could outlast man.  Imagine if humans destroyed each other with nuclear, chemical, or biological weapons.  With a penchant for rapid breeding, rabbits could rapidly recolonize the world after the warlike species, Homo sapiens, annihilated itself.

Georgia is home to 4 species of rabbits, and during the Pleistocene the southeast also harbored at least 2 kinds of hares.  At various times the lagomorphs (hares and rabbits) may have been more abundant (as a biological mass) than any single species of megafauna.  Scientists interpeted a fossil site near Gainesville, Florida to have been a dire wolf den because they found a skull belonging to Canis dirus in association with hundreds of rabbit bones.  Rabbits must have been an easy and abundant food source, more reliable than any single species of megafauna.  Rabbits easily survived the Pleistocene extinction event that wiped out many of the larger, fiercer animals.  The meek really did inherit the earth.

Here’s a review of rabbit and hare species found or formerly found in Georgia.

Rabbits

Eastern Cottontail–Sylvilagus floridanus

Photo of an eastern cottontail from google images.

While this species is by no means endangered, there are likely far fewer than there were as recently as 50 years ago.  Suburbs and shopping centers are replacing the early successional forests they prefer.  And the natural areas we let remain are maturing into older stands of timberland which is not as favorable a habitat for rabbits.  Rabbits like young forests with saplings, shrubs, and grassy open areas.  This type of habitat was abundant during the Pleistocene, thanks to rapid climate fluctuations, unchecked fires, and megafauna foraging.

New England Cottontail–Sylvilagus transitionalis

In a blog entry from a few weeks ago I listed the species found at the Ladds fossil site and mistakenly noted, about the New England cottontail, that I thought it was doubtful a subspecies could be determined based on a bone.  I didn’t realize the New England cottontail was a distinct species, not just a subspecies.  Today, the New England cottontail is being considered a candidate for the endangered species list.  Hunters introduced the eastern cottontail to New England, and it is doing well, but the New England cottontail is not adapting to suburbanization and is restricted to a small number of locations.  It looks much like an eastern cottontail.  They can hybridize with eastern cottontails in captivity but won’t do so in the wild.  Before advances in DNA research, scientists had to compare skulls to determine whether a cottontail was an eastern or a New England.  But now scientists can analyze the DNA of rabbit scat to identify species.  However, the fossil specimen from Ladds that Clayton Ray identified as a New England cottontail was probably an Appalachian cottontail.

Appalachian cottontail–Sylvilagus obscura

Photo of an Appalachian cottontail.  They look exactly like New England cottontails.  Only DNA analysis can determine the difference.  For that matter, visual inspection can’t differentiate between this and the eastern cottontail.  A skull comparison or a DNA anlysis is necessary for species determination between those species as well.

This species wasn’t identified or recognized until 1992.  Before then, it was considered the same species as the New England cottontail.  Scientists noted enough genetic differences to mark it as a distinct species, though there is academic debate about this.  Again, visual determination of live speciments can’t distinguish the difference between this and the eastern cottontail.  Instead, DNA tests or skull measurements are necessary.  The Appalachian cottontail inhabits heath balds in the north Georgia mountains.

Swamp rabbit–Sylvilagus aquatica

As this photo from google images shows, swamp rabbits readily take to water.  This is the rabbit that attacked President Carter.

Many readers of this blog may be too young to know about an event that occurred involving this species during the presidency of Jimmy Carter.  On vacation from the presidency Jimmy Carter sat in a canoe and fished a  Georgia swamp.  A swamp rabbit attacked his boat–probably the only instance when a sitting president was attacked by an animal.  I guess the rabbit was swimming in the swamp and felt threatened by the canoe.

Swamp rabbits occur alongside rivers and streams in the Georgia piedmont.  They’re known as canecutters because they eat bamboo cane which used to grow in thick stands many miles long in low areas of central Georgia.  Though canebrakes are rare today, swamp rabbits still can reside near the existing and numerous beaver ponds, another favored habitat.

Marsh rabbit–Sylvilagus palustris

Photo of a marsh rabbit from google images.

The range of this species takes up where the swamp rabbit’s leaves.  Whereas swamp rabbits occur in low areas of the piedmont, marsh rabbits inhabit coastal plain wetlands.

Hares

Antelope Jackrabbit–Lepus alleni

 

 

Photo of an antelope jackrabbit from google images.

Fossil hunters occasionally find jackrabbit bones in florida.  Antelope jackrabbits inhabited the southeast until, at least, the middle Pleistocene (~300,000 BP).  Dry climate phases created large scale grassland and even desert-like chapparel habitats where antelope jackrabbits shared the range with pronghorns, cheetahs, and camels.  As I speculated in my blog entry “The disjunct range of the burrowing owl,” a corridor between western grasslands and eastern grasslands must have existed until the Stagell Interglacial.  Forested habitats increased during this lengthy interglacial, and this probably ended the occurrence of many western species (though not all) in the east.  The skeleton of a large unnamed extinct species of jackrabbit, estimated to be about 2 million years old, has also been discovered in Florda.  Both species undoubtedly occurred in what’s now Georgia.  Today, antelope jackrabbits must be considered a relic species, restricted to southwestern deserts.

Snowshoe hare–Lepus americanus

 

 

Lynx attacking a snowshoe hare.  Photo from google images.

Fossil evidence proves Arkansas was home to snowshoe hares during the last Ice Age.  It’s quite possible snowshoe hares occured in north Georgia during the Pleistocene, and they probably lived in what’s now Tennessee.  Arkansas is well south of the present day range of this species.

Red Stewed Rabbit

In my irregular series on this blog, “If I could live in the Pleistocene,” I imagine living 41,000 years ago in what’s now east central Georgia but with modern conveniences such as a nice adobe brick home with solar-powered electricity, woodstoves,  running water from a well, and fresh produce grown in a well protected garden. (See my September and December archives) Though I raise poultry and milk cows in this imaginary utopia, I try to utilize as much game and fish as I can.  Rabbit would likely have to be an item in my diet, though I’m not too keen on killing them–their alarm call sounds like a human baby crying.  In real life I’ve experimented with rabbit and have learned that it is a good stewing meat.  Rabbit is all white meat with a flavor slightly superior to chicken.  If you’ve never had it, and someone served it to you, and you didn’t notice the different bone structure, you would think you were eating chicken. There’s not much fat on a rabbit but that’s the only part that might taste a little unusual in my opinion.

Many people fry rabbit like chicken.  It’s ok this way but I think a little dry.  Other cooking methods are apt to make the rabbit have a rubbery texture.  That’s why I recommend stewing rabbit in a crockpot.  Here’s the best recipe for rabbit I know.

Marinate a disjointed rabbit in 1 cup of soy sauce, 2 tbls of vegetable oil, 2 tbls of honey, 1 bunch of chopped green onions, and 5 spice powder and ginger powder to taste.  Place the rabbit pieces and the marinade in the crockpot and cook for 6 hours.  The meat falls of the bone.  A little bit of the sauce goes a long way–it’s a marinade, not a gravy, but a couple of sp0onfuls will season a side of egg noodles well.

Rabbit meat stewed in a crockpot with just onions, water, and salt also makes a good base for a Brunswick stew.  Just shred the meat, remove the bones, and add crushed tomatoes, cooked potatoes, canned limas, canned corn, and red and black pepper.