Relict Ice Age Microfauna of Georgia’s Boulderfield Forests

Spruce trees and northern pine species dominated the higher elevations of Georgia’s Blue Ridge Mountains during Ice Ages.  The highest peaks may have even been above the tree line and likely hosted grassy steppes or plants found today in the tundra region.  Severe freeze-thaw cycles of Ice Age winters broke big slabs of rock into boulders that  cover many north facing slopes of the southern Appalachians.  Following the most recent Ice Age, the climate warmed and northern species of hardwoods recolonized these boulderfield forests from refugia that probably existed adjacent to rivers and creeks.  Boulderfield forests have shallow rocky soils dominated by 20-30 foot tall stunted trees, and a great variety of beautiful shrubs.  Frequent high winds and ice storms keep boulderfield forests relatively open by knocking over trees and breaking limbs.  The most common trees include yellow birch, black birch, mountain maple, sugar maple, striped maple, beech, basswood, mountain ash, yellow buckeye, fire cherry, and serviceberry.  Northern red oak and white oak also occur.  Mountain laurel, rhododendron, witch hazel, climbing hydrangea, hazelnut, prickly gooseberry, rasberry, blackberry, strawberry bush, and elderberry grow in the understory,  Moss covers the boulders.  Some examples of boulderfield forests in Georgia are Brasstown Bald, Coosa Bald, Hightower Bald, Eagle Mountain, and Grassy Mountain.

Mountain Laurel growing alongside the trail on Brasstown Bald.  I hiked up and down this mountain 2 years ago but didn’t know about boulderfield forests then.  I do remember the stunted birch and beech trees and the abundant boulders. 

Birch trees are well adapted to boulderfield forests because they can germinate on top of rocks and logs.  The sugar in sugar maple sap lowers the freezing point, allowing this species to survive in colder climates.  Basswood sends lateral roots around boulders, helping them grow in rocky soils.

The abundant rocky crevices here provide shelter to many disjunct populations of small animals that formerly ranged into the piedmont and upper coastal plain during the Ice Age, but whose ranges have since contracted as the climate warmed.  Four species of northern shrews still live on the  peaks of the southern Appalachians which serve as islands of habitat surrounded by land that has become unsuitable for them.  Pygmy, long-tailed, smoky, and masked shrews thrive in boulderfield forests too cool for competing cold-blooded lizards.

Masked shrew.  Boulderfield forests on high peaks are too cool for their main ecological competitors–lizards.

The masked shrew (Sorex cinereus), like most insectivores, has a high metabolism and eats 3 times its own weight in insects everyday. (Imagine a 200 pound man eating 600 pounds of food everyday.)  They can hide in crevices under the abundant boulders and forage in the adjacent leaf litter.  The masked, pygmy, and smoky shrews all had a wider distribution during much of the Pleistocene than they do today.

Red backed vole

Fossils of the red backed vole (Myodes gapperi) have been found in central Georgia at Little Kettle Creek in Wilkes County.  Today, for the most part, this species ranges no farther south than Kentucky, but disjunct populations occur in some boulderfield forests in north Georgia.  These omnivorous mouse-like mammals eat green plants, fungi, seeds, roots, berries, snails, and insects.

Red squirrel.  They prefer forests dominated by spruce, pine, and hemlock.

The red squirrel (Tamiasciurus hudsonicus) reaches the southernmost limits of its range on the northfacing slopes of Georgia mountains.  Fossils of red squirrels have been found farther south in 2 Bartow County sites–Ladds and Kingston Saltpeter Cave, indicating this species too ranged farther south during the Ice Age.  They prefer seeds from conifers but will  also eat acorns, nuts, fungi, tree sap, and birds eggs.  They have an interesting habit of storing caches of food in hollow logs, tree snags, and crevices…far more than they need.  Native Americans use to utilize these caches to stave off starvation.

Red squirrel cache of pine cones.

Saw whet owl

The saw whet owl (Aegolis acadicus) nests in Georgia’s boulderfield forests, but they do not breed any farther south.  These tiny owls stay still to avoid detection and predation.  This defense mechanism misleads many people into thinking they are tame.  This species likely bred farther south during the Ice Age.

Winter wren.  I saw one of these for the first time last Thanksgiving.  They hop around on the ground like a mouse.

The winter wren (Troglodytes hiernalis) is a common inhabitant that breeds in boulderfield forests.  They do tend to migrate farther south during the winter.  This past Thanksgiving, I saw a winter wren hopping around like a mouse behind the Woodbridge Dam in Evans, Georgia.  They forage for insects in crevices and caves, hence the Latin name, troglodytes, which means cave dweller.

Other common animals with northern affinities that occur on boulderfield forests include deer mice, chipmunks, ruffed grouse, and yellow bellied sapsuckers.

See also: http://markgelbart.wordpress.com/2011/06/10/brasstown-bald-the-highest-mountain-in-georgia/

and http://markgelbart.wordpress.com/tag/miccosukee-gooseberry/

Piedmont Cliff Ecology

Cliffs represent some of the most pristine natural environments left in the temperate zone .  Developers have little use for them, though some are transformed into stone quarries and ruined.  Cliffs are the best examples of environments that have remained unchanged since the Pleistocene.  Aside from a few bird extinctions and extirpations, they host about the same ecological communities now as they did a million years ago. 

Cliffs are common in the Blue Ridge Mountains of north Georgia but many are found in the piedmont region of the state as well.  Cliffs located in the piedmont offer the southeasternmost available habitat for species that depend upon this type of environment.  In the piedmont cliffs consist of erosion resistant rock that forms vertical or almost vertical bluffs adjacent to rivers.  There are cliffs along the Chattahoochee and Flint Rivers.  Some cliffs are mountains that rise well above the surrounding landscape.  Currahee Mountain in Stephens County, the southeasternmost extension of the Blue Ridge Mountains, rises 800 feet above the surrounding landscape.  Big Mountain in Oglethorpe County is 100 feet higher than the local topography.  Pine Mountain in Harris County reaches an altitude of 1,395 feet above sea level and has many cliffs.

Currahee Mountain in Stephen’s County.  It is located in the piedmont, just a few miles from the Blue Ridge region.  Note the radio towers.

Chattahoochee River Bluff. 

Sprewell Bluff adjacent to the Flint River

Tallallulah Gorge.  This is in the Blue Ridge Mountains, not the piedmont.  I visited this site in the Summer of 2004 before I started writing this blog.  I remember descending a stairway to the gorge and coming face to face with a black vulture, a species confortable at such heights.

Cliffs adjacent to rivers provide ideal nesting and roosting habitat for many species of birds.  Nests located on cliffs are difficult for mammalian predators to access.  The vantage point of a cliff allows predatory birds, such as peregrine falcons, to see potential prey on the river below.  Flying insects abound over river water, attacting swallows and bats.

Black vultures and turkey vultures use cliffs for roosting and nesting.  During the Pleistocene California condors, terratorns, and possibly Grinnell’s crested eagle used cliffs in Georgia.  However, most species of vultures also make use of tree snags.  Formerly, the peregrine falcon almost exclusively nested on cliffs.

Peregrine falcon nesting on a building in Atlanta.  These falcons use skyscrapers as a substitute for cliffs.  The skyscrapers mimic their original preferred habitat.

The peregrine falcon (Falco peregrinus) is also known as the duck hawk because ducks are a favored item of their diet.  They formerly were common in north Georgia where cliffs are abundant and likely nested as far south as the piedmont cliffs.  J.J. Audubon reported seeing 50 peregrine falcons on a 4 month trip down the Mississippi River to collect bird specimens, but I’ve never seen one in the wild.  They were extirpated from the state about 100 years ago–hunters used to shoot birds of prey for the hell of it, causing the local demise of golden eagles as well.  But with the help of recovery programs, they’ve returned to the state.  Instead of re-occupying natural cliffs, they’ve taken residence on big city skyscrapers that mimic their natural habitats.  They find plenty of prey in city pigeons which were also originally cliff dwellers.

Peregrine falcons are spectacular birds capable of reaching a speed of 200 mph when they are descending upon prey.  They usually attack flying birds, especially ducks, pigeons, blackbirds, and blue jays.  They are the only predatory bird crows are afraid to mob.  The chimney swift may be the only bird fast enough to outmaneuver it.  Peregrine falcons aggressively take over cliff nesting sites, chasing away not only all ravens but eagles 4 times their size.  There is a case on record of a peregrine falcon killing a golden eagle by chasing it into a cliffside.  The following youtube video shows a peregrine falcon knocking out and probably killing a red-tailed hawk that ventured too close to its nest. http://www.youtube.com/watch?v=Hpz66RYD110

J.J. Audubon observed peregrine falcons learning to associate the sound of a hunter’s shotgun with a dead duck.  Peregrine falcons frequently used to steal ducks dispatched by human hunters.  One individual falcon learned to enter a hole in Audubon’s pigeon coop and began taking a pigeon every day until Audubon shot it.  Audubon noted that peregrine falcons eat dead fish, but apparently they don’t normally prey upon mammals or reptiles.

Golden eagle feeding on a red fox that it killed.

Golden eagles (Aquila chrysaetos) primarily nest on cliffs and also formerly ranged into Georgia.  Eagle Mountain, Georgia may be named for the golden eagles that used to nest there.  They take large prey for a bird–juvenile deer, turkey, goose, raccoon, and skunk, but they mostly feed upon rodents and rabbits.  Bald eagles like to nest on cliffs too but will more readily build big stick nests in trees.

Cliff swallows building mud nests.

Cliff swallows (Petrochelidos pyrrhonatus) build mud nests on the sides of cliffs and catch insects flying over water.  They’ve learned to build nests under bridges all across the state, and I see them flying in the vicinity of just about every bridge I drive over during summer.

Ravens formerly nested on Georgia’s cliffs but are now considered rare stragglers in state.  Other birds that like to nest on cliffs include red-tailed hawks, great horned owls, barn owls, eastern phoebes, Carolina wrens, goldfinches, grackles, and mourning doves.

Some mammals reside in cliff environments.  Bats roost in overhangs, rock shelters, and caves.  Raccoons, woodrats, and chipmunks can climb to dens less frequented by predators.  Cougars are also known as mountain lions because they have enough agility to climb cliffs where there are safe denning areas for kittens.  During the Pleistocene other big cats and dire wolves would not have been able to reach these dens.  The ability to traverse rugged terrain gave cougars an advantage over other larger predators then and may explain why they were able to co-exist with low populations of humans for so long when other carnivores weren’t.

Enough soil washes onto ledges that plants can take root.  Lichens cover exposed rock.  Chestnut oak, sand hickory, winged elm, red maple, red cedar, shortleaf pine, and Virginia pine grow on cliff ledges in the Georgia piedmont.  So do shrubs such as blueberry, century plant, rhododendron, and mountain laurel. Povery oat grass, bluestem, rock-pink, violets, Carolina lilly, coreopsis, and rockcap fern are some examples of ground cover decorating cliff ledges.

References:

Audubon, J.J.

Audubon: Drawings and Writings

Penguin Books 1999

Larson, D.W.; Uta Matthes, and Peter Kelly

Cliff Ecology: Pattern and Process in Cliff Ecosystems

Cambridge University Press 2005

When Pleistocene Megafauna Roamed Interdunal Wetlands

My parents used to own a beachfront condo on Harbor Island, South Carolina.  One year, I was surprised to find a freshwater marsh in front of the condo, complete with cattails, frogs, and red-winged blackbirds.  The marsh was located behind a beach dune where it did not exist just a year earlier.  This type of environment is known as an interdunal wetland, and they can form rapidly.  The East Beach freshwater marsh on St. Simon’s Island formed in just 2 months.  Rain washes beach wrack (dead plants and detritus) into the swales between dunes, creating enough topsoil for freshwater species of aquatic plants to take root.  Heavy rains keep the marsh wet, and the dunes prevent drainage.  The water table at sea level is often close to the surface, and because fresh water is lighter than sea water, it remains on top, providing habitat for fresh water species.

Whitney Lake on Cumberland Island, Georgia.  Note the alligators.  It’s a freshwater interdunal wetland with an outlet to the ocean.  Storm surges of saltwater that kill woody plants keep it open.  The state of Georgia has the least developed coast on the Atlantic side of North America.  Most of Georgia’s barrier islands are not accessible via automobile.

Aerial photo of St. Catherine’s Island, Georgia.  The brown represents upland maritime forests of live oak, loblolly pine, and palm trees.  The green represents freshwater, brackish, and saltwater marshes.  About 40,000 years ago sea level was near  present day sea level and some of this island consists of sediment accumulated then.  Then, as the ocean receded, that sediment underlay oak hammocks  surrounded by miles of grassy savannahs.  About 6,000 years ago, sea level rose to this approximate location again and sediment is currently accumulating and building on the old Pleistocene sediment.

Interdunal wetlands located behind beachfront dunes may form rapidly, but they can also be short-lived.  Storm surges can breach beach dunes, resulting in an influx of salt water, followed by drainage.  However, storm surges may play a role in maintaining older freshwater marshes located in the middle of a barrier island well away from the beach.  The influx of salt water kills shrubs and trees.  Eventually, rainwater reduces salinity and shade-intolerant aquatic vegetation becomes re-established.

Feral horse drinking water from Whitney Lake on Cumberland Island.  Interdunal freshwater ponds acted as an oasis for Pleistocene megafauna surrounded by unpotable ocean water and salt marshes.  Horses and hogs run wild on some of Georgia’s barrier islands today.  The presence of megafauna on barrier islands during the Pleistocene wasn’t a problem because natural predators controlled their populations.  Today, large herbivores can overgraze vegetation and cause harmful erosion unless human hunters or wranglers take action.

Freshwater ponds and marshes on barrier islands are like an oasis surrounded by undrinkable ocean water and vast salt marshes.  During the Pleistocene these sources of fresh water would have attracted every species of megafauna living on a barrier island.  Giant ground sloths, mammoths, mastodons, bison, horses, tapirs, llamas, peccaries, deer, capybara, and giant beaver were all drawn to the drinkable water and highly edible plants that grew in the marshes.  Predators, such as dire wolves and big cats, would have lain in wait at these water holes.  The location of interdunal marshes may explain the abundance of Pleistocene fossil sites in this region.  There are 9 above sea level, Pleistocene-aged fossil sites near the Georgia coast (Fossilosa, Isle of Hope, Mayfair, Porter’s Pit, Savannah River dredgings, Turtle River dredgings, Clark’s Quarry, and Watkin’s Quarry) compared to 3 sites in the Ridge and Valley Region and just 1 site in the Piedmont Region.  Animals attracted to freshwater marshes occasionally died there and were buried by sediment carried by storm surges.  This combination of factors explains why there are more Pleistocene fossils found near the coast than anywhere else in the state, though there are other depositional origins for some of the sites here as well.

Today, megafaunal species living on Georgia’s barrier islands include white-tail deer, feral horses and hogs, some exotic species of introduced deer, and alligators.  Paleontologists have noticed the relative lack of alligator fossils found in the Pleistocene sites near the Georgia coast, where they would be expected to be abundant.  Apparently, alligators did range here during the Pleistocene, but it may be that egg-eating mammals kept their populations in check.  Jaguars probably directly preyed upon adults.  Interdunal wetlands also host marsh rabbits, raccoons, mink, otters, wading birds, ducks, and songbirds that would otherwise be absent due to the lack of freshwater.

Mosquito fish (Gambusia holbrooki).  It’s well adapted for life in interdunal wetlands.  They are related to those tropical aquarium favorites–guppies.

Killifish, mosquito fish, top-nosed minnows, mullet, and gars thrive in interdunal ponds.  Mosquito fish are well adapted for this type of environment.  They eat their own weight in mosquito larva everyday, giving them the energy to reproduce rapidly–a population of 7,000 can increase to 120,000 is just 5 months.  This allows them to quickly colonize newly created marshes and improves their chances of survival during storm surges.  Mosquito fish can endure high temperatures and high levels of salinity that would prove fatal to most other species of fresh water fish.  Bream are also found in some interdunal ponds, but scientists don’t know whether they occur naturally or were introduced by man.

Botanists recognize 4 successional stages of interdunal wetlands.  The first is an open water stage with floating plants such as duckweed and emergent vegetation including cattails, pickerel weed, and arrow-arum.  The second stage has less open water and is dominated by cattails and pickerel weed.  The third stage is a grassy shrub stage with saw grass (of Everglades fame), cordgrass, sedges, buttonbush, rose mallow, and wax myrtle.  The final stage is a woods of red maple, Carolina willow, tupelo, and water oak.  A storm surge of saltwater can kill the trees and return the marsh to the open water stage.  Below are some photos of some shrubs commonly found in interdunal wetlands.

Buttonbush (Cephalanthus occidentalis) is common on the edges of interdunal wetlands.  A study of fossil mastodon dung found buttonbush to be a common item in their diet in Florida.  Mastodon foraging faciliated the spread of the seed-filled buttonballs which float.  A mastodon tearing apart a buttonbush was beneficial to the plant species’s long term survival.

Carolina willow (Salix caroliniana) with egret nests.

Wax myrtle (Myrica cerifera).  The wax rendered from the berries is used to make candles.  Euell Gibbons states that the leaves can be used for seasoning soups and stews, like bay leaves. 

Rose mallow (Hibiscus moscheutos), a common and beautiful plant found growing in interdunal wetlands.  The roots were used to make marshmallows.  All modern marshmallows sold in grocery stores are made artificially without mallow roots.

The Mystery Cat of Pleistocene Georgia

Most small species of cats are adept tree climbers, but the margay (Leopardus wiedii) excells. It hunts, copulates, and raises its young in trees, making it as arboreal as a monkey or squirrel.

The margay is about the size of a large house cat.  It is an arboreal species.

The margay is able to climb head first down trees, and its wrists are built much like those of a squirrel’s.  Click on the below link to the youtube video of a margay.  Note how it can hang upside down using just its rear paws.  Note also its athletic ability to leap from tree limb to tree limb.

http://www.youtube.com/watch?v=ef129AsFfMA

The margay is a nocturnal hunter, preying upon birds, birds’ eggs, frogs, lizards, rodents, monkeys, and probably bats.  They also eat fruit.  Like tigers, they use audible mimicry to lure prey.  They’ve been observed imitating the cries of a baby monkey to attract parent monkeys to their doom. (Tigers imitate the mating bugle of elk.)  Not all prey is defenseless, however.  Brazilian squirrels gang together and drive margays away.

Today, the margay ranges throughout Central and South America, but fossil evidence of a margay-like cat has been found from 12 sites in Florida and 2 in Georgia.  Jaw bones of this mystery cat come from Ladds in Bartow County, Georgia and the Isle of Hope site in Chatham County near Savannah–evidence this species occurred throughout the state during the Pleistocene.  The fossils from all the sites where this species has been found likely date from a warm interglacial period.  Some scientists think these fossils represent an extinct species (Leopardus amnicola), while others consider it an extinct, large subspecies of margay (Leopardus wiedii amnicola).  The modern margay requires dense forest habitat, and it’s likely this species or subspecies did too, probably explaining why its fossils are found in deposits dating to interglacial periods.  During interglacials forested habitats expanded.

Sketch of the jaw bone of a cat found at the Ladds fossil site.  Click to enlarge.  Dr. Clayton Ray thought this specimen was most like the jaw bone of a jaguarundi, but other scientists have concluded it’s from a cat that was more like a margay.  This page is from the below referenced paper authored by Dr. Ray.

Photo of a jaw bone of a cat found at the Isle of Hope site near Savannah, Georgia. Click to enlarge.  Every measurement of this specimen falls within the size range of both margay and jaguarundi.  This means it can’t be conclusively identified.  It’s slightly smaller than most specimens identified as Leopardus amnicola.  Page from the below referenced study authored by Dr. Hulbert.

The ocelot (Leopardus pardalis) is about the size of a bobcat or maybe a little larger is some cases.  Unlike the margay, it’s primarily a ground dweller, though it can climb trees.  It mostly feeds upon rodents.  Today, ocelots range throughout Central and South America and rarely into south Texas and Arizona.  In the 19th century, they were found in Louisiana and Arkansas, and fossil evidence of this cat has been found from 2 sites in Florida, also probably dating to a warm interglacial.

The ocelot and margay shared a common ancestor.  It’s likely that some individuals of this ancestral species preferred hunting on the ground and their decendents evolved into ocelots, while other individuals preferred hunting in the trees and their decendents evolved into margays.  Males that were good tree climbers were more likely to meet females that were good tree climbers, and they passed on the beneficial genes that gave them their natural ability.

The ocelot can grow to a size as heavy as 40 pounds.  Also used to range into southeastern North America.

The jaguarundi (Puma yagaouroundi) is a 3rd species of small neotropical cat.  It was formerly classified in its own genus by some scientists and lumped in the Leopardus genus by others, but genetic studies suggest it is closely related to the cougar (Puma concolor).  I hypothesize that an isolated population of cougars began specializing in small prey to avoid competition with larger carnivores such as jaguars, saber-tooths, and lions.  This population then evolved into jaguarundis.  Studies show cougars regularly take smaller prey than jaguars, and there isn’t much overlap in their prey selection.  In some locality with scarce prey, competition may have forced the ancestral population to take even smaller prey.  Today, the jaguarundi preys upon birds, rodents, opposums, small species of deer (brocket), reptiles, and insects.  It eats fruit as well.  It ranges throughout Central and South America and rarely south Texas.  100 years ago, some were introduced to Florida, and a small population may still exist there.  Reported sightings continue.

The jaguarundi may have ranged into southeastern North America as well.  It’s also known as the otter cat due to its cylindrical shape.  It’s closely related to the cougar but is about 10% its size.

It’s evident at least 2 species of neotropical cats colonized southeastern North America during warm climatic phases of the Pleistocene.  I hypothesize that they continued to live in the region until approximately 28,000 BP.  Dense forests remained widespread in the region until then.  Between ~28,000 BP-~15,000 BP prairies, desert scrub, and spruce woodlands replaced the kinds of forests margays and ocelots prefer, though it’s possible they persisted near the coast where ocean currents kept the climate from deteriorating.  If it wasn’t for man, I think ocelots and margays would have recolonized the south.  Fossils of margays have been found in Texas, and they date to 4400 BP, showing they were more widespread recently.  However, native Americans coveted their beautiful coats, and I suspect human hunters prevented the re-expansion of their range.

References:

Hulbert, Richard; and Ann Pratt

“New Pleistocene (Rancholabrean) Vertebrate Faunas from Coastal Georgia”

Journal of Vertebrate Zoology 18 (2) June 1998

Ray, Clayton

“Pleistocene Mammals from Ladds, Bartow County, Georgia”

Georgia Academy of Science Bulletin 25 (3) 1967

The Natural Communities of Georgia by Leslie Edwards, Jonathan Ambrose, and L. Katherine Kirkman

The Natural Communities of Georgia is a beautiful and exhaustive encyclopedia of all the natural environments that exist within the state boundaries.  It’s an updated version of the late Charles Wharton’s 1978 book–The Natural Environments of Georgia.  This book is dedicated to him.

The Natural Communities of Georgia was published by the University of Georgia Press in February 2013 after almost a year’s delay.  It’s reasonably priced by Amazon at $46, considering it is a hardback with 674 pages, hundreds of color photographs, and dozens of illustrations and maps.  Color photographs can make a book prohibitively expensive to produce.  I eagerly purchased a copy of this book as a birthday present to myself.

Although 3 co-authors are given credit for writing this book, there are an additional 12 contributing authors listed inside, making this book quite a collaborative effort.  They could have used me as a contributing writer for the section about the Pleistocene.  They covered the Pleistocene in 2 or 3 paragraphs, and because it was the end of the chapter, most of the rest of the last page was blank.  People who regularly follow my blog know I could have easily filled that big blank page with interesting information about Pleistocene Georgia.  Whoever wrote their brief section about Pleistocene Georgia slightly missed the mark about 1 tidbit of trivia.  The author listed some of the mammal species found in Georgia during the Pleistocene and included the ocelot followed by the word, possibly, in parenthesis.  This isn’t entirely incorrect.  An individual fossil of an ocelot was found in Florida, so ocelots may have roamed Georgia then.  But I’m sure the author was referring to specimens found in 2 fossil sites in Georgia that represent a species from the Leopardus genus which includes the margay and the jaguarundi, not the ocelot.  I’ll write about these finds in my next blog entry and clear up that author’s confusion.

The format of The Natural Communities of Georgia is convenient for the reader.  The book is organized into 5 parts corresponding to the 5 ecoregions of Georgia.  The authors give an overview of each ecoregion, then discuss each type of environment found within the ecoregion.  Sidebars featuring an animal or plant commonly found in each environment are included.  Sidebars showing featured places where an example of each environment can be found conclude each section.  Detailed directions are given, so the reader can use the book as a guide to seek out each type of environment.  The following is a list of all the natural environments discussed in the book along with an example featured place.  I’ve already discussed and/or visited some of these sites.  A * denotes the ones I’ve either already blogged about or have visited.

BLUE RIDGE ECOREGION

*Northern Hardwood and Boulder Forest–The Summit of Brasstown Bald

Montane oak forest–Whitney Gap Trail on Wildcat Mountain

Cove Forest–Sosebee Cove Trail

Low to Mid elevation oak forest–Bear Hair Gap Trail

*Pine-Oak woodlands–Tallulah Gorge State Park

Ultramafic Barrens and Woodlands–Davidson Creek Botanical Area

High Elevation Rock Outcrops–Blood Mountain

Low to Mid elevation Domes, Glades, and barrens–Bog Cedar Mountain

*Low to mid elevation acidic cliffs and outcrops–Tallulah Gorge State Park

Mountain bogs–Songbird Trail at Lake Conasauga

Seepage Wetlands–Track Rock Gap Archaeological Area

Spray Cliffs–Helton Creek Falls

Flood Plains, bottomlands–Jacks River Trail

CUMBERLAND RIDGE AND VALLEY ECOREGION

Mesic Forest–Shirley Miller Wildflower Trail

*Dry Calcareous Forest–Chickamauga Battlefield Park

Acidic Oak-Pine-Hickory–Cloudland Canyon State Park

*Pine Oak woodland–Zahnd Natural Area Lookout Mountain

*Montane longleaf Woodland–Berry College

*Calcareous Cedar Glades–Chickamauga Battlefield Park

*Calcareous Prairie–Berry College

Acidic Glades–Rocktown

Calcareous Cliffs–Pigeon Mountain Wildlife Management Area

Acidic Cliffs–Cloudland Canyon State Park

*Flatwoods–Berry College

Calcareous Seepage Fens–Mosteller Springs

Acidic Seepage Wetlands–Keown Falls Tract

*Sagponds–Zahnd Natural Area

Floodplains, bottomlands–Coosa River Lock and Dam Park

PIEDMONT ECOREGION

Mesic Forest–Chicopee Woods

Oak-Pine-Hickory–Chicopee Woods

Pine-Oak Woodlands–Red Cockaded Woodpecker Trail

Prairies–Pickett’s Mill Battlefield Park

Granite Outcrops–Davidson-Arabian Mountain

Glades, Barrens–Kennesaw Mountain

*Ultramafic Barrens–Burke’s Mountain

Flatwoods–Monticello Glades in the Oconee National Forest

Seepage Wetlands–Dawson Forest Wildlife Management Area

Floodplains, Bottomlands–Alcovy Conservation Center

COASTAL PLAINS ECOREGION

*Sand Dunes–Ohoopee Dunes Natural Area

Dry Upland Longleaf Pine Woodland–Reed Bingham State Park

Mesic Longleaf Pine Woodland–Silver Lake Wildlife Management Area

Dry Evergreen Oak Woodland–Big Hammock Natural Area

Dry Deciduous Hardwood Forest–Providence Canyon Recreation Area

Mesic Slope Forest–Montezuma Bluffs Natural Area

Granite Outcrops–Broxton Rocks

*Eocene Chalk Prairie–Oaky Woods

Pitcher Plant bogs–Doe run pitcher plant bog

Shrub bog–Townsend Wildlife Management Area

Cypress-Gum Pond–Big Dukes Pond Natural Area

Depression Oak Forest–No publicly available area

Riverine floodplains, bottomlands–Ebenezer Creek Boat Ramp

*Bottomland Hardwood–Moody Forest

River Banks Levees–Altamaha Park

Small Stream Floodplain Forest–Little Ocmulgee State Park

Okefenokee Swamp–Okefenokee Swamp National Refuge

MARITIME ECOREGION

Intertidal Beaches–Jekyll Island

Maritime Dunes–Jekyll Island

Maritime Forest–Crooked River State Park

Interdunal Wetlands–Jekyll Island

Salt Marsh–Earth Day Nature Trail

Freshwater and Oligohaline Tidal Marsh–Butler Island Altamaha Wildlife Management Area

Tidal Swamp–Lewis Island Wildlife Management Area

I’m going to use The Natural Communities of Georgia as a reference in future blog entries, focusing on their paleo-origins.  Much of my rumination will be speculation.  Some of these environments, such as open pine savannahs. are ancient and may have originated as early as the Cretaceous, though with significant floral and faunal turnover.

Oh, and I’m making a note to self here to buy The Road Side Geology of Georgia when that book is published.

The Orianne Indigo Snake Preserve

It’s too late to save most of North America’s megafauna.  Man overhunted most of the magnificent animals on this continent into extinction thousands of years ago, and Europeans nearly eradicated the rest within historical times.  But it’s not too late to save an apex predator of the southeastern coastal plain–the indigo snake (Drymarchon couperi).  A private charitable group, the Orianne Indigo Snake Society, is purchasing land and negotiating with other large landholders to manage their property for the benefit of this snake.  Their goal is to protect 48,704 acres of land within the Orianne Indigo Snake Preserve.  Presently, they own 2,607 acres and have permission to manage an additional 8,678 more acres (mostly owned by lumber companies) for the benefit of the snake.  This seems like a lot of land, but male indigo snakes require as much as 3000 acres of habitat because they are top predators, in fact predators of predators.

Images from the Orianne Snake Society website.

The preserve is located along the Ocmulgee River where there are many sandhills.

Indigo snake range map.  They were extirpated from Alabama decades ago.

Orianne Society volunteer with an indigo snake.  Strippers like to use indigo snakes in their acts because they are long and docile, seldom biting humans.  It’s the largest North American species of snake.

Indigo snakes require 2 different types of habitat.  During winter they den in gopher tortoise burrows located in open pine savannahs with sandy soils, but during summer they forage in shaded bottomland swamps.  They need access to both environments unobstructed by manmade structures, such as busy roads where automobiles take a heavy toll.  Modern day development makes areas with vast acreages of both types of habitat rare.  Moreover, open pine savannahs have been replaced with pine tree farms which are inadequate habitats for gopher tortoises.  Indigo snakes can survive on pine tree farms without gopher tortoises, as long as the lumber operators leave refuse piles for the snakes to seek refuge during colder months.  Indigo snakes also make use of armadillo dens and hollow logs.  The Orianne Society manages habitat by conducting prescribed burns which improve habitat for gopher tortoises, and by encouraging lumber operators to leave debris piles.

Indigo snakes were extirpated from Alabama.  Indigo snakes are a major predator of venomous snakes, and copperhead populations skyrocketed in Alabama, since indigo snakes disappeared there.  The Orianne Society has a captive breeding program.  Two years ago, they began releasing indigo snakes in the Conecuh National Forest in Covington County, Alabama.  Eventually, this may help reduce copperhead populations.

Indigo snakes are primarily forage hunters, though ambush hunting has been recorded.  They actively travel over land and capture other animals, especially snakes.  They bite their prey and thrash and bash the animal into submission.  One study found that 85% of their diet included gopher tortoises, snakes, and rodents.  They are immune to rattlesnake poison and commonly feed upon diamondback rattlesnakes.  They are cannibalistic, so human breeders of captive indigoes keep them in separate enclosures.  They also scavenge.  One was observed feeding on a dead shark, and they will eat fish in captivity.  Scientists suspect indigo snakes feed on fish stranded in shrinking pools during droughts, much like cottonmouth water moccasins do.   Another individual was observed ambushing 5 rufous-sided sparrows by a single puddle when the birds came to drink and bathe.  These behaviors show they are both active and passive feeders.  They’re big eaters despite being cold blooded reptiles.  A species of indigo snake native to Central America was observed feeding on a boa constrictor, then on a jumping viper before the former was digested.

There are 5 species of indigo snakes in the Drymarchon genus.  In addition to the one that lives in North America, 4 species live in Central and South America.  The genus is closely related to black racers.

The Orianne Indigo Snake Preserve protects several species of big snakes.  The indigo snake frequently grows to 7.5 feet long with a record length of 8.5 feet, but this only beats the record length of the coachwhip snake (Masticophis flagellum) by 1.5 inches.   Diamondback rattlesnakes (Crotalus adamateus) have been known to reach a length of 8 feet long, and pine snakes (Pituophis melanaleucus) get to 5 feet long.

Diamondback rattlesnakes grow to 8 feet long but occasionally fall prey to indigos.

Coachwhip snakes get their name because they are shaped just like a whip.  They are almost as long as indigos but are much skinnier.  They come in many different color variations.

Rainbow snakes (Farancia erystrogramma) grow to 3-4 feet long.  These snakes are also found on the Orianne Indigo Snake Preserve.  They burrow in sand and mud in swamps.  They specialize in feeding on eels.

By contrast southeastern crown snakes reach lengths of just 10 inches.  They specialize in feeding upon centipedes.  There are 3 species which diverged following sea level rises that isolated founding populations.

Fort Stewart has some of the best remaining habitat for big coastal plain snakes.  Here, the federal government is free to conduct prescribed burns that improve wildlife diversity, plus there are fewer roads and no real estate development on the base.  Live fire exercises on this and other army bases in Georgia also improve habitat for wildlife by igniting fires.  More species of snakes have been recorded from Fort Stewart than any other area of the state–33 species.  So far, just 21 species of snakes are known to occur on the Orianne Indigo Snake Preserve, but as this area becomes better studied that number will grow.  Fort Stewart is home to bald eagles, wood storks, and healthy populations of wood ducks, fox squirrels, deer, and wild boar.  If this military base is ever closed, I hope it’s protected as a wildlire preserve.

Most North American snakes have been recorded in the Pleistocene and Pliocene fossil records, and scientists think most of today’s existing snake genuses originated early in the Miocene.  Snakes are an ancient part of the ecosystem, and it would be a shame, if we lost any individual species.

References:

Stevenson, Dirk; et. al.

“Prey Records for the eastern Indigo Snake (Drymarchon couperi)”

Southeastern Naturalist 9 (1) 2010

http://www.oriannesociety.org/

The Evolutionary History of the Black Bass Genus (Micropterus sp.)

Scientists used a molecular clock to determine all 8 species of black bass share a common ancestor that lived 11 million years ago.  The molecular clock is a method scientists have of estimating the age of a species.  It’s especially helpful when studying the evolutionary history of organisms that are absent or rare in the fossil record.  It is based on the assumption that DNA  protein sequences evolve at a relatively constant rate.  Scientists assume a substitution rate of appearance of new mutations in each member of the population.  Scientists eventually learned the substitution rate varies among different kinds of organisms, so they calibrate the molecular clock with the fossil record and known geological events that may have caused species divergence.  This involves a lot of computer modeling and statistics, but they are confident that using a molecular clock is a reliable method of estimating evolutionary ages.

The oldest bass fossil ever found was unearthed in Texas and dated to 23 million BP.  Scientists estimate the Micropterus (black bass) genus originated about 26 million years ago, based on molecular clock data.  This suggests their findings are consistent with the fossil record.  Today, there are 8 species of bass that began to diverge from a common ancestor 11 million years ago when a marine transgression flooded most of the coastal plain in the southeast.  This dramatic rise in sea level isolated many populations of bass, resulting in allopatric speciation.  Scientists believe this is the most common type of speciation, and it occurs when founding populations become geographically isolated.

Range map of 8 species of black bass.  The dots represent collecting localities for specimens used in study.  From “Speciation in Micropterus” referenced below. Click to enlarge.

Time calibrated phylogram showing evolutionary history of black bass.  This is also from “Speciation in Micropterus.”  The scientific names translated to common names are: Micropterus punctulatus–spotted bass, M. dolomieu–smallmouth bass, M. coosae–redeye bass, M. cataractae–shoal bass, M. notius–Suwannee bass, M. treculi–Guadulupe bass, M. salmoides–largemouth bass, M. floridanus–Florida largemouth bass.

The common ancestor of smallmouth and spotted bass diverged from the ancestor of the other 6 species of bass during the marine transgression of 11 million BP.  Later rises in sea level between 8 million BP-2.5 million BP further resulted in the evolution of redeye, shoal, Suwannee, Guadalupe, largemouth, and Florida largemouth basses.  Before this study scientists thought speciation of bass occurred due to climate perturbations of the Pleistocene, but now they realize most Micropterus species evolved before Ice Ages began.  Only the divergence of spotted bass and smallmouth bass occurred during the Pleistocene about 1 million years BP. These sister species may have been isolated from each other by a glacier, but the other species of bass originated in warmer climates that remained glacier-free.

Most black bass species readily hybridize, showing just how closely related they are.  This can prove a problem when a common species is introduced to waters occupied by a rare species.  Shoal bass were formerly abundant in the rocky cataracts found in the Flint, Chattahoochee, and Appalachiacola Rivers, but most of those areas were inundated with reservoirs that make the habitat unsuitable.  Shoal bass became rare, and to make matters worse spotted bass were introduced.  Spotted bass compete for the same foods and hybridize with the remaining shoal bass.  

Comparison photos and illustrations between 4 species of bass.  The bottom photo is of a a redeye bass.  It has a curious distribution.  It’s found in 2 different river drainages–the Coosa and the upper Savannah.  At one time these 2 drainages must have been connected.

The below link has some nice photos comparing the shoal bass with other species of bass.

http://www.flmnh.ufl.edu/fish/sharks/shoalbass/ShoalAbstract.htm

White bass (Morone chrysops), striped bass, (Morone saxatilis), and black sea bass (Centrophis stiata) are not closely related to the Micropterus genus, despite their common names.  Instead, the Micropterus genus is part of the Centrarchid family that includes sunfish and crappies.  Surprisingly, largemouth bass can hybridize with some of their distant sunfish and crappie relatives.

Adult largemouth bass prey on smaller fish, frogs, crayfish, and occasionally birds and mice.  Most of the largemouth bass’s sister species grow smaller and feed more on insects and small crayfish.  Smallmouth and spotted bass feed on prey intermediate in size between that taken by the largemouth and its 6 sister species.  The largemouth bass’s range overlaps with those of its sister species, but they occupy different ecological niches.  The introduction of intermediate feeders, like the smallmouth or spotted, may disrupt the ecosystems in southern rivers.

Largemouth bass are some times found in brackish waters located within salt marshes.  Anglers catching them here still call them by their archaic common name of “green trout.”

References:

Near, T.J.; et. al.

“Speciation in North American black bass, Micropterus (Achioptergii: Centrarchidae)”

Evolution 57 (7) 2003

http://www.yale.edu/eeb/near/14.pdf

Simon, Ho

“The Molecular Clock and Estimating Species Divergence”

Nature Education 1 (1) 2008

The Unknown Owl of Pleistocene Georgia

A few scraps of bone found at just 2 fossil sites in Georgia indicate a now extinct species of owl, larger than any present day owl species, used to live in the region.  Starrs Olson compared a mandibular symphysis discovered on Ladds Mountain, Bartow County with those from a great horned owl (Bubo virginianus), a snowy owl (Nyctea scandiaca), and a great gray owl (Strix nebulosa).  On a human the mandibular symphysis is the cartilage in the front dimple of the chin that connects the left jaw bone with the right jaw bone, but on a bird it’s the lower bill.  The unknown species of owl’s lower bill was significantly larger than those from the extant largest species of owls.

Photo comparing the mandibular symphysis of the unknown Pleistocene species with those from the 3 largest species of extant owls.  It’s the largest lower bill, suggesting this extinct species was larger than any North American owl species still extant.

David Steadman examined all the bird fossils excavated from Kingston Saltpeter Cave, also located in Bartow County, and he came across 2 unusually stout tarsometatarsii from juvenile owls that didn’t match the measurements from any known species of owl.  The tarsometatarsi is a bird’s equivalent of an ankle bone.

Tarsometatarsii from vultures and condors.  I couldn’t find any photos on the web of owl tarsometatarsi.

Those 2 specimens from Kingston Saltpeter Cave either belong to the same species that Starrs Olson examined, or they belong to yet another unknown extinct species.  Neither paleo-ornithologist was willing to describe a new species based on such scant evidence, even though it’s fairly certain a large unique owl did exist here during the Pleistocene.  This case reminds us of why the La Brea Tar Pits are of such value to science.  A different extinct Pleistocene owl also used to live in the American southwest.  It’s known as the Brea owl and was recently given the new scientific name Oraristrix brea.  At least 23 individual Brea owls became trapped in the tarpits, leaving scientists with many specimens to examine.  But if it wasn’t for the tarpits, there’s barely enough evidence to recognize this animal as a species because just a few fossil specimens of this owl have been found at 2 other sites in Arizona and Mexico.

The unknown Georgia species was likely a spectacular bird that would have impressed any human who had a chance to see it.  Like most large predatory birds, it probably lived in low population densities.  Let’s assume an average of 1 individual lived per 10 square miles, and that an average owl’s lifespan was 3 years.  Let’s also assume this bird had a limited geographical range of about 60,000 square miles ( the area of present day Georgia).  And suppose this animal existed as a species for 1 million years.  I did the math: 1.8 billion individuals of this undescribed species of owl lived on earth, and the only evidence we can find is a lower bill and a couple ankles.  Moreover, there’s no evidence at all of its immediate evolutionary ancestor.  My calculations show just how low the odds of an organism becoming a fossil can be, especially for a forest bird that successfully can avoid dying in a flood when the possibility of being covered by sediment and preserved is higher.  No Pleistocene fossils of ivory-billed woodpeckers or Carolina parakeets have ever been found either, though parakeet fossils from the Pliocene have been unearthed in Nebraska.

Scientists are interested in finding more fossils of this owl.  Besides earning the honor of naming a new species, they want to unravel the possible evolutionary relationship between this large owl, and the extinct giant Cuban owl (Ornimegalonyx), a flightless owl that served as top predator there until its extinction when man disrupted the environment.  The unknown Georgia owl was probably not flightless because it would have faced too much competition from large mammalian predators.  Its shorter, stouter legs suggest it was also not likely a ground dweller, like the Brea owl of the southwest.  Nevertheless, it undoubtedly was at least a fearsome predator as the 3 large owls below.

Great horned owl with captured skunk.  The great horned owl is the heaviest extant species.  They’ve been known to prey on tom cats and they regularly prey on skunks, squirrels, rabbits, turkeys, and grouse.

The lower bill of the unknown extinct species was 25% larger than that of this species, the great gray owl.  If the overall body proportions were the same, than the extinct Pleistocene owl of Georgia was probably about 25% larger  than this species as well.

Snowy owls have been known to attack small house dogs.  The extinct Pleistocene species that used to live in Georgia was also likely a fearsome predator of small mammals.

What caused the extinction of this mystery owl?  I believe a large fearless owl living in low population densities was easily overhunted by men.  According to George Leonard Herter, owl meat is as white and flavorful as chicken.  They reportedly have large drumsticks.  There’s also the possibility that this owl scavenged meat for part of its diet, and the extinction of the megafauna reduced its food supply.  Or this owl may have had a narrow ecological niche that disappeared at the end of the Pleistocene.  Whatever the reason for its extinction, it’s a shame that we know so little about this animal.

References:

Campbell, Kenneth; and Zbigniew Dochinski

“A New Genus for the Extinct Late Pleistocene Owl Strix brea (Aves: Strigiformes) from Rancho La Brea”

Australian Museum of Natural History 62 (1) 2010

Olson, Starrs

“A Very Large and Enigmatic Owl from the late Pleistocene at Ladds”

Special publication of the Carnegie Museum of Natural History 1984

Steadman, David

“Fossil Birds from Kingston Saltpeter Cave, Bartow County, Georgia”

The Late Pleistocene Record of Kingston Saltpeter Cave, Bartow County, Georgia edited by Joel Sneed and Larry O. Blair

Inland Shorebirds of the Pleistocene

The Scolopacidae family includes birds that are commonly considered denizens of the sea shore, such as sandpipers and curlews, but 3 species are primarily terrestrial inhabitants.  The upland sandpiper (Bartramia longicauda), also known as the golden plover or Bartram’s plover, is the one most easily recognizable as a relative of its familiar sea shore cousins.   However, it preferes grassy environments where it feeds upon insects and grass seeds instead of marine worms, clams, and fiddler crabs.  Upland sandpipers were formerly an abundant bird of the prairies on the Great Plains and in the midwest, but market hunting destroyed the primeval population, and farmers replaced prairie grasses with fields of wheat and corn that are unsuitable habitats for this bird.  In March 1821 just 1 market hunter killed 48,000 upland sandpipers, demonstrating how abundant they used to be.  (They were regarded as a delicacy by Creole cooks.)  This bird will never regain its former abundance, but the remaining population is adapting to new anthropogenic grasslands–abandoned strip mines and airports.  

Upland sandpiper.  They are a ground nesting bird that feigns injury to draw predators away from their eggs and nestlings.

The upland sandpiper is a summer migrant to North America, and it winters on the Pampas of South America.  Aside from an occasional vagrant, this bird is presently absent from the southeast, but it was a common species in this region during the Pleistocene.  Fossil evidence of upland sandpipers, dating to the late Pleistocene, were found in Kingston Saltpeter Cave, Bartow County, Georgia and in Bell Cave in Northern Alabama.  This geographical area was mostly forested then, but extensive grasslands must have also existed because upland sandpipers favor nearly treeless habitats.

Both the above mentioned fossil sites yielded remains of the woodcock (Scolopax minor) as well, another terrestrial member of the Scolopacidae.  This bird uses its unusually long bill to probe moist earth for worms and grubs.  They are year round residents in the south, but much of the population migrates north for the summer.

Woodcock.  In Ohio they are arriving a month earlier in spring than they did 100 years ago due to global warming.

Woodcocks spend their days hiding in the woods but feed in open areas at night.  They favor 2nd growth woods with thickets that are adjacent to agricultural fields where they can hunt for earthworms in the tilled soil.  Like upland sandpipers, woodcocks are much less common than they used to be because of hunting and habitat loss.  In the Pleistocene south woodcocks likely were abundant because megafauna foraging and sudden climate fluctuations created mixed environments of young and old forests, thickets, and grasslands.  Moreover, large predators such as wolves and big cats kept numbers of foxes, raccoons, and possums relatively low, reducing nest predation.  The south was a refuge for woodcocks during the height of the Ice Age.  Genetic studies suggest the woodcock population expanded rapidly following the retreat of the glaciers as more habitat became available.

Male woodcocks display by making a “peent” call before flying in wide spirals above their potential mates.  The females lay eggs on the ground and carry their young with them for 18 days until the nestling learns to fly.  Then in late summer when they moult, woodcocks can’t fly and must hide in thickets, thus explaining why they need varied habitats.

Wilson’s snipe (Gallinago delicata) is another species of terrestrial Scolopacidae.  They live and nest in marshes where they hunt for worms, grubs, insects, and some plant matter.  They are an erratic fast flyer, making them difficult to shoot, hence the origin of the word, sniper.  Wilson’s snipes have a curious pattern of migration.  They winter in the southeast as well as in South America and migrate over dry land in the late winter and early spring.  But when they migrate south, they travel over the coast.  This explains why there are an additional 9 species of snipe endemic to various islands.  Storms blew some flocks off course where they found permanent refuge on isolated oceanic islands.

Wilson’s snipe–a marsh bird.  Their habit of migrating south over the coast has resulted in speciation on isolated islands.

Even some coastal species of Scolopacidae occasionally find their way far inland.  Joel McNeal photographed stilt-legged sandpipers, lesser yellowlegs, black necked stilts, pectoral sandpipers, long-billed dowitchers, American avocets, western sandpipers, and semi-palmated sandpipers foraging on the sod farm that surrounds the Etowah Indian Mounds in Bartow County.  Here’s a link to his photos. http://www.pbase.com/joelmcneal/bartowbirds

The Coats-Hines Pre-Clovis Site in Williamson County, Tennessee

Workers constructing the 13th hole of the Crockett Springs Golf Course in 1977 unearthed mastodon bones.  Paleontologists took note of the discovery and 17 years later when they learned lots adjacent to the golf course were going to be transmogrified into residential housing, they surveyed a nearby drainage ditch and found another partial mastodon skeleton along with fossils of horse, deer, a canid, muskrat, turkey, painted turtle, and frog.  This time they also discovered evidence that attracted archaeologists–10 stone tools, 24 lithic flakes, and part of a bone spear tip embedded in a mastodon bone.  The tools included a bifacial knife and hide scrapers made from local Fort Payne chert.  Moreover, there were butcher marks on the mastodon backbone, suggesting these ancient Americans removed the proboscidean’s tenderloin.  The apparently butchered mastodon bone yielded radiocarbon dates translated to ~14,000 calender years BP.  Archaeologists regard this as the pre-Clovis era.

Williamson County, Tennessee. 

Photo of the Nashville Golf and Country Club which was formerly known as the Crockett Springs Golf Course.  I couldn’t find a photo of the 13th hole where the mastodon bones were found.  I don’t know which hole this is.

A 3rd survey of the drainage ditch in 2005 found parts of yet another mastodon, and a few years later in this generous spot they found fragmentary evidence of a large Pleistocene mammal, but it was in such poor condition, it couldn’t be identified.  Underneath this, they recovered a Pleistocene-aged deer antler.  In 2010 the owners of the new house built next to the drainage ditch gave permission to the archaeologists to dig a deep trench in their backyard.  Here, the archaeologists found 1582 fragmented bones of mastodon, deer, turkey, turtle, and frog along with 11 more human made artifacts all located 10 feet below the surface of the yard.

Mastodon bones found in trench.

Mastodons roaming future golf course.

The home owners were nice enough to let archaeologists dig this deep trench in their backyard.  I had a trench like this dug in my backyard a few months ago.  Unfortunately, they didn’t find any fossils.  They were replacing the drainage line for my septic tank.  Cost me $5,000.

Geologists think the Coates-Hines site was an intermittent pond that existed between 22,000 BP-12,000 BP.  A stream periodically became blocked, creating the pond, then on occasion it drained.  I propose beavers were the agent that blocked the stream.  Every so often, predators would kill all the beavers in this locality, and the dam would fall into disuse and break down.  A new population of beavers would recolonize the site, and the cycle would begin anew.  About 12,000 years ago, rain washed soil down the adjacent hillside and buried the old pond site and stream with colluvial sediment.

The ancient beaver pond provided an ideal location for a Paleo-Indian base camp.  The ancient Americans opportunistically ambushed big game that browsed aquatic plants, but they also had easy access to muskrats, turtles, fish, frogs, and edible plants such as cattails.  All the species of fossil animals found at this site are notably edible.

Reference:

Wolf, Aaron; Jesse Tune, and John Broster

“Excavations and Dating of Late Pleistocene and Paleoindian Deposits at the Coats-Hines Site, Williamson County, Tennessee”

Tennessee Archaeology 5 (2) Fall 2011

http://csfa.tamu.edu/cfsa-publications/Tune-TA5-2011.pdf