Salt Domes of Texas and Louisiana

August 25, 2016

Salt domes are fascinating geological structures of ancient origin.  Over 500 subsurface salt domes have been mapped in Texas, Louisiana, and Mississippi.  During most of the Mesozoic Age from 150 million years BP to 65 million years BP a shallow inland sea covered this region.  The Western Interior Seaway periodically dried, leaving vast salt deposits.  Later, when the ocean re-filled the basin; loads of sediment, sea shells, and coral reefs were deposited on the layers of salt.  Sedimentary rocks such as sandstone, shale, and limestone formed from these deposits.  Meanwhile, organic rich mud buried under these layers was transformed into petroleum.  On the surface of the earth salt is a solid crystal.  But deep underground where it is heated and under high pressure, salt becomes malleable–like toothpaste.  All those miles of sedimentary rock squeeze the salt upward (and sometimes sideways and downward), not unlike an hand squeezing a tube of toothpaste.  This process explains the shape of salt domes.

The top of salt domes comes into contact with ground water.  The chemical reaction of ground water + salt dome creates cap rock, consisting of sulfur, calcite, gypsum, and anhydrite.  Miners extract and process these materials because they have wide industrial and agricultural uses.  The structure of sedimentary rocks on the edge of the salt domes often trap petroleum, so oil wells are drilled adjacent to them as well.

salt domes of the East Texas Basin

Illustration of subterranean salt domes in Texas.

Illustration of a typical salt dome.  They often trap petroleum deposits.

Cattle grazing on top of Damon Mound, an above ground salt dome located in Texas.

Cretaceous Western Interior Seaway

A shallow sea existed over Texas and Louisiana during the Mesozoic.  It repeatedly dried out, concentrating vast amounts of salt.

Although there are hundreds of known subsurface salt domes in the region, just an handful breach the surface.  Damon Mound in Texas (near Houston) is an example of an aboveground salt dome.  It rises 80 feet above the surrounding coastal plain.  Avery Island, Louisiana is another aboveground salt dome.  It is a forested hill, surrounded by salt marsh.  The cap rock here contains Pleistocene-aged sediments where the remains of prehistoric mammals including mammoth, mastodon, Harlan’s ground sloth, Jefferson’s ground sloth, horse, and bison have been excavated.  The Mcilhenny family grows tobasco peppers on Avery Island for their famous hot sauce.  Hugh Mcilhenny, founder of the company, discovered some of these bones after the Civil War.  He kept them on display but the specimens were lost after his death, then later re-discovered by 2 professors.  Some were sent to the Smithsonian Museum and others were sent to LSU and Tulane.  In 2012 they were returned to Avery Island where they are available for display upon request.

The Inner Space Cavern Fossil Site near Georgetown, Texas

August 18, 2016

Construction workers building an highway bridge over a railroad line accidentally discovered Inner Space Cavern in 1963.  This site is located on the edge of the Edward’s Plateau 1 mile south of Georgetown, Texas.  The eastern side of the Edward’s Plateau is a hilly landscape sitting on Cretaceous-age limestone bedrock.  Rain dissolves limestone creating many underground caves in the region.  The workers drilled down 33 feet and when the drill bit reached the cavern it fell an additional 24 feet becoming lodged in stalagmites.  Inner Space Cavern is also known as Laubach Cave, named after the family who owns the land.  The Laubachs opened up an accessible entrance to the cave, and it is now a tourist attraction.  The cave is underneath the rail line and Highway 35.  Skeletal remains of late Pleistocene age vertebrates have been excavated from 5 sites in the cave.  However, radiocarbon dating of these specimens was executed during the late 1960s and early 1970s when this technology was still in its infancy, and the resulting dates are not considered accurate.  The specimens are at least 13,000 years old, but it’s unclear if they can even be radiometrically dated.

Location of Georgetown, Texas

Location of Georgetown, Texas.  Inner Space Caverns is just south of this town.

Inner Space.

View inside Inner Space Cavern.

An unique assemblage of grazing fauna roamed central Texas during the late Pleistocene.  Mammoth, bison, horse, camel, glyptodont, and a large extinct species of pronghorn (Tetrameryx shuleri) occupied the plains.  The fossil record suggests Tetrameryx shuleri was restricted to what is now the state of Texas during the late Pleistocene.  Because it was a regional species, it was more vulnerable to extinction when man colonized the area.  A single specimen of the scimitar-toothed cat (Dinobastis serum) was found in Laubach Cave.  Although this species ranged widely over North America, the distribution of its remains suggests the region from Texas and Oklahoma to western Tennessee may have held a core population.  Other large mammal remains found in the cave include Jefferson’s ground sloth, deer (probably white tail rather than mule), flat-headed peccary, jaguar, dire wolf, and the extinct Florida spectacled bear (Tremarctos floridanus).  This is the westernmost known occurrence of the Florida spectacled bear during the late Pleistocene.

Today, the Texas kangaroo rat (Dipodomys elator) is restricted to 10 counties in north Texas bordering Oklahoma.  Remains of this species found in Laubach Cave show it formerly ranged further south.  Black-tailed prairie dogs (Cynomys ludovicianus) and meadow voles (Microtus pennsylvannicus) also no longer occur this far south.  Short-tailed shrews (Blarina carolinensis) don’t live this far west any more.  The presence of these small mammals suggests the climate in this region was wetter with cooler summers during the Ice Age than it is today.

Texas kangaroo rat (Dipodomys elator).  Skeletal remains of this species dating to the late Pleistocene were found in Inner Space Cavern.  It no longer occurs this far southeast.

Skeletal remains of this extinct pronghorn (Tetrameryx shuleri) were found in Inner Space Cavern.  This was its easternmost known occurrence. Note the 4 prongs.

Evidence from Inner Space Caverns shows the extinct Florida spectacled bear (Tremarctos floridanus) lived as far west as central Texas.

The faunal composition of Laubach Cave indicates this region during the Ice Age was dominated by grassy plains but with some riparian woodlands and mesquite/acacia scrubland.  Grazers such as mammoth, horse, and camel clearly are evidence of prairie habitat.  The presence of Jefferson’s ground sloth, deer, cottontail rabbit, spectacled bear, and jaguar (an ambush predator)  make it seem likely that finger shaped communities of trees grew alongside rivers and creeks.  These riparian woodlands probably consisted of centuries old live oaks, cottonwoods, and sycamores.  Flat-headed peccaries, jackrabbits, and kangaroo rats prefer (or in the case of the extinct species, preferred) scrub habitat.  Texas kangaroo rats almost exclusively burrow beneath the roots of mesquite.

Vegetation of this region was similar to that of today, yet slightly different.  The moderate increase in precipitation combined with cooler summer temperatures meant deeper top soils and greater stream flow through rivers.  The alternate climate caused changes in the abundance and density of some species of plants.  Prairies were mixed with some tall grass and some shortgrass, depending upon the topography.  These prairies, like many other natural communities, were thick with wildlife until man came along.

Reference:

Sansom, Jones; and Ernest Lundelius

“Inner Space Cave: Discovery and Geological and Paleontological Investigation”

Austin Geological Society Bulletin 2005

If I could Live During the Pleistocene Part 13–Making Insecticide from Tobacco

August 15, 2016

This is the newest installment of an irregular series I write for this blog about my favorite fantasy.  I daydream that I traveled back in time to east central Georgia 36,000 years ago where I enjoy a life of self-sufficiency but with modern conveniences. (See: https://markgelbart.wordpress.com/category/if-i-could-live-during-the-pleistocene/ ) In my fantasy world I have a farm surrounded by a high stone fence that keeps mastodons and bears from raiding my garden and orchard, but it recently occurred to me this wall wouldn’t stop insect pests.  As an experiment in my real world yard, I planted peach trees from seed.  Most fruit sold in grocery stores comes from mutated varieties grafted on root stocks because fruit trees don’t produce the same quality from seed, but peaches reportedly are an exception.  Some sources claim peaches grow true to seed, while others say peaches grown from seed are inferior.  My peach trees started to bear this year, and the ones I salvaged tasted as good as farmer’s market peaches.  Unfortunately, most of the peaches fell off or were ruined because of an insect pest known as plum curculio (Conatrachelus nenophar), a little beetle in the true weevil family.  This experience made me realize I needed to revise my fantasy and make my own insecticide, if I want to have fruit at my Pleistocene homestead.  In the modern world I can buy the most delicious local peaches, nectarines, and plums; but I won’t have any fruit in the Pleistocene without spraying.

This is one of my least damaged peaches.  Most of the others fell off long before they ripened.  In some localities spraying fruit is necessary.

I won’t spray until after the petals fall off because I don’t want to poison the butterflies and bees that pollinate the flowers.

plum curculio

Plum curculio.  This species of beetle destroyed all of my peaches.  It is abundant in my neighborhood probably because of the presence of wild plums and cherries.

Plum curculios are common in areas with wild plum and wild cherry trees.  They readily adapted to fruits introduced by Europeans, especially peaches.  The adult females burrow into unripe fruit and make a crescent shaped hole where eggs are deposited.  The crescent shape keeps the larva from being crushed when the fruit grows.  Most fruit falls off the tree, and any fruit that ripens is blemished so badly it can’t be sold.  The trees must be sprayed as soon as the flower petals fall and again when the fruit is in the shuck stage.

 

 

 

 

 

 

 

Tobacco plants.

It is easy to make insecticide from tobacco (Nicotiana tabacum).  Tobacco is in the nightshade family, a group of plants that evolved the ability to produce toxins in their leaves.  These poisons prevent insects and other animals from consuming the leaves.  To make insecticide mix 1 cup of dried tobacco leaves with 1 gallon of water and let it sit in the sun for 24 hours.  Then add 3 tablespoons of liquid soap.  (Just think: people who smoke cigarettes are smoking insecticide.)  The nicotine in tobacco destroys an insect’s nervous system.

I’d have to grow tobacco in my Pleistocene world, but I wouldn’t smoke it.  I prefer marijuana.

 

The Nature of Trials of the Earth by Mary Hamilton

August 10, 2016

One of the last great stands of wilderness in eastern North America existed along the Mississippi River during the late 19th century.  Loggers ruined this environment between 1880-1910, but in Mary Hamilton’s autobiography, Trials of the Earth, she described the awesome nature of this region.  Though her book focuses on her personal life and all the tragedies and hardships her family endured, I collected all of the interesting tidbits of natural history that she wrote about.

A fascinating book about the pioneer life of a woman in Mississippi and Arkansas during the turn of the 19th century.

In 1896 Mary Hamilton, along with her 2 young children and her brother and sister, followed her husband to a logging camp on Concordia Island, Mississippi.  The island was bound by a chute of the Mississippi River and the main channel.  Her husband was a supervisor at the camp, and he was too busy to bring her himself.  Instead, he marked a wagon trail through the wilderness, and a guide (actually an inexperienced teenaged boy) helped her find the camp where she eventually worked as a cook for 30 lumberjacks.  She was accustomed to this work, having boarded over 100 lumberjacks at a previous camp.

The family settled in a big white tent.  The island consisted of a dense forest of large mature oak, sweetgum, hackberry, and tulip trees with a thick undergrowth of bamboo cane that grew all the way to the lower limbs of the tall trees.  (See: https://markgelbart.wordpress.com/2013/01/28/canebrakes-are-forlorn-landscapes/)  Closer to the river, the forest thinned out, probably because of frequent flooding, and enormous sycamores and cottonwoods grew here.

The lumberjacks felled the trees and lashed them together in rafts to be tugged down the river to sawmills.  Some species of trees float, while others sink, so the lumberjacks had to lash “floaters” with “sinkers.”  Sweetgum and oak sink and had to be lashed to cottonwood, ash, or cypress.

Some species of trees sink, while others float.  Lumberjacks had to lash logs from “floaters” with logs from “sinkers” when they sent them downstream to the mills.

This is how people with wagons crossed rivers before bridges were built.  People who owned the ferry charged for its usage.

Mary’s younger brother was an accident prone Gomer Pyle type, and her husband was afraid he would hurt himself or somebody else, if they put him to work as a lumberjack.  Therefore, they assigned him the task of hunting and fishing to supplement their supplies.  It was difficult to supply this camp with food.  During times of high water, wagons couldn’t reach the camp, and supply wagons occasionally got lost in the wilderness and never arrived.  Sometimes the man in charge of the supply wagon ignored the grocery list and bought candy and cakes instead of the staples they needed.  So hunting was useful.  Deer and black squirrels were abundant.  Apparently, the black phase of the fox squirrel (Scirius niger) was the only species of squirrel on this island.  This surprises me because gray squirrels (Scirius carolinensis) prefer the kind of dense forest Mary describes.  In the south fox squirrels generally prefer more open woodlands.

Black phase of the fox squirrel.

One day Mary’s brother encountered a mother bear playing with her cubs.  He threw down his gun and ran for his life, yelling “there’s a dozen lions after me.”  Bears were plentiful on the island, and the lumberjacks’ diet here included bruin along with local beef and pork (wild hogs ran wild everywhere) and corned beef from New Orleans.  Animals took advantage of the lumber camp as a source of food as well.  A bear stole a quarter of a beef left to hang outside one night.  Raccoons, opossums, and bobcats fought over the camp garbage every night, and Mary heard panthers screaming and wolves howling nightly.  Later, when her family moved to an homestead on the nearby Sunflower River she insisted her husband shine the lantern on her when she went outside to bring in the laundry every night  because she heard a panther screaming regularly on both sides of the river.  People didn’t know much about panthers and wolves then and were very afraid of them. Mary didn’t consider all nature unpleasant.  She liked to hear the birds and frogs in the spring, and one day she collected 5 gallons of blackberries the size of Guinea hen eggs.  The rich delta soil produced berries larger than modern cultivated ones sold in farmer’s markets.

Mary’s husband built a “freshwater shrimp” trap for her brother.  The trap worked and captured bags of “shrimp” everyday, but her brother didn’t know “shrimp” meant crawfish.  He always threw away the crawfish until he was informed of his ignorance.

The Mississippi River shifted direction during their time on Concordia Island.  This caused a near disaster.  The river started eroding the bank overhanging all the rafts of lumber.  The rafts could have become covered in sediment and lost.  They immediately sent for tugboats that hauled the floating rafts and most of the logs were saved.  This event, referred to as “sloughing,” must have been an impressive sight.  Trees fell into the river, and the sediment collapsing made a “boom, boom” sound.

Next, Mary’s family moved to a lumber camp near the Sunflower River, a tributary of the Yazoo.  This region too was all canebrake and woods where panthers screamed and wolves howled every night.  Getting water at this camp was laborious and difficult.  Iron pipes were driven into the ground to reach well water, but oftentimes this was hard water high in magnesium and calcium.  Hard water is safe for drinking but can’t be used for washing dishes or clothes.  Mary softened the water by adding lye made from wood ashes.  The addition of a base binds the calcium and magnesium ions, making the water usable for cleaning.  Too much water became a bigger problem at this camp.  Rainy weather flooded all the surrounding bayous, isolating the camp from civilization, and they ran short of food.  They realized the rising water was going to completely inundate the camp and the wooden clapboard house where they were living.  So Mary’s husband cut a path through a canebrake that led to an Indian mound located above the floodplain, and he built a small boat.  The boat wasn’t big enough for all of them, and he had to make 2 trips to save his wife and 3 children.  Mary waited with her 5 year old daughter and infant son for 6 hours, while her husband carried their other small child to safety and returned.  She spent all this time standing on a chair on the highest ground, holding her baby and comforting her young daughter.  The baby slept the entire time, despite the rain.  She saw a bear, deer, rabbits, mice, and snakes swimming by them, looking for high ground.

Tornadoes often storm up the Mississippi River valley, then turn inland and smash through forest.  Mary describes one such area that was known as “the cyclone,” an area estimated to be at least 36 square miles.  “The cyclone,” located near the present day site of the Parchman State Penitentiary, was an eerie landscape without a single standing tree.  Instead, the ground was littered with fallen timber covered in grapevines, poison oak, and thorny brier bushes.  Ecologists call these environments windthrows.  This windthrow was on rich soil and hosted luxuriant tangles of vegetation, making the area impassable.  Mary tells the story of a well-liked Jewish paymaster who chose to take a shortcut through “the cyclone” rather than travel the 5 mile path around it.  He was bringing the pay to a neighboring lumber camp.  He got lost for 4 days and went half-mad from panic and dehydration.  The thorns tore all his clothing off as he scrambled through the briers.  Search parties failed to find him.  He finally wandered close to the camp, completely naked and incoherent but with the money in his hand.

Mary Hamilton described an area near the present day site of Parchman Penitentiary as “the cyclone.”  It was a windthrow of at least 36 square miles covered in an impenetrable stand of vines, briers, and cane.

Mary worked hard most of her life, but shortly after she married she did enjoy a bit of a vacation in Missouri where she stayed with friends by the Castor River.  Here, she learned how to fish.  She mostly caught bass, but on one early morning before anyone else was awake she caught an eel.  This sent her screaming in terror back to the house.  She was so scared she didn’t let go of the rod and carried the eel to the front door.  Mary wanted to get rid of it, but her husband was from England where eel is considered a delicacy, and he prepared it for supper.  One kind of fish that Mary caught here was referred to as a “white salmon.”  It took a little research, but I determined her “white salmon” was actually a walleye (Sender vitreus).  The old Ozark term for walleye is “jack salmon.” 

Mary caught bass, an eel, and walleye (which she called “white salmon”) in the Castor River.

I’d like to live in a wilderness where panthers scream and wolves howl every night.  And it would be rewarding to live off the land, gardening and raising animals for food.  But I wouldn’t want to do this without modern conveniences.  Mary worked from dawn to past dusk for most of her life.  I envy the wilderness she got to see but not the hard life she endured.

 

 

Pleistocene Roadrunners (Geococcyx californianus)

August 5, 2016

Roadrunners are neotropical invaders that spread across North America, probably no earlier than the late Pleistocene.  Fossil remains of roadrunners dating to this time period have been excavated from sites in Arizona, New Mexico, and California.  Roadrunners are ground foraging birds in the cuckoo (Cuculidae) family.  All other members of this family prefer the tree canopy.  There are just 2 species of roadrunner–Geococcyx californianus ranges from central Mexico west to California and east to Arkansas and Louisiana and G. velox occurs in tropical deciduous forests from southern Mexico to Nicaragua.  The ancestor of these species likely diverged during an arid climate cycle of the Pleistocene.  G. californianus evolved a preference for desert scrub and cactus environments and moved north across the Rio Grande.  I think they are a fairly recent colonizer of this region because desert grassland and scrub habitat was widespread across southeastern North America during the late Pliocene/early Pleistocene about 2 million years ago, yet there is no fossil evidence of roadrunners in this region from that time period.    If roadrunners lived in southwestern North America during this early time period when their ideal habitat was so widespread, I believe they would have colonized the southeast.  And they would still persist in some areas of the southeast where favorable habitat exists.  There’s no shortage of thickets mixed with clearings in the southeast.  In Arkansas, the easternmost part of their modern range, roadrunners occur in farms and clearings, cedar glades, scrubby woods, and rocky outcroppings.  Currently, the Mississippi river appears to be a barrier that prevents them from expanding their range east.  They haven’t crossed the river yet because they are weak flyers and prefer to run in zigzag patterns between thickets.  They are the fastest runners among birds capable of flight, reaching speeds of 25 mph–about the speed of an Olympic male sprinter.

Roadrunner and Snake

 

 

 

 

 

 

 

 

Roadrunner killing snake.  They kill their prey by bashing it against the ground until it is senseless.

Geococcyx californianus map.svg

Roadrunner range map.  I believe the Mississippi River is the barrier that keeps them from expanding their range east.

Video of a roadrunner ambushing an hummingbird at a feeder.

247b;h84

Real life roadrunners are smart like their cartoon imitation.

Pleistocene roadrunners were slightly larger than modern roadrunners but are considered to be the same species.  Scientists believe they grew to a larger size due to cooler Ice Age summers.  The modern smaller birds have more endurance in warmer conditions than larger birds and can chase down their favored prey (lizards, snakes, mice, scorpions, insects, and other birds) for longer periods.

Roadrunners are poorly studied.  I searched The Auk and The Condor, 2 ornithology journals, for more information about them and found very few articles..  They are an intelligent bird, not unlike their cartoon counterpart, and this makes them hard to study because they are smart enough to avoid traps.  This is 1 case when the cartoon imitation of an animal matches its real personality.

 

Passenger Pigeons (Ectopistes migratorius) and Forest Succession

August 1, 2016

The former abundance of the now extinct passenger pigeon amazed all of the pioneers who witnessed their migration and roosts.  Some researchers estimate passenger pigeons composed 25% of the total bird population in eastern North America during colonial times.  Their migrations consisted of billions of birds that could eclipse the sun for as long as 14 hours.  Pigeon dung fell like “snowflakes” underneath this eclipse.  They nested in enormous colonies, covering many square miles.  Their survival strategy was predator satiation.  With synchronized hatching there were billions of squabs on the forest floor during the week they left the nest and were learning how to fly.  There were just too many for predators to eat all at once. They nested and reproduced in the great deciduous and coniferous forests of the Midwest, then migrated to the middle south during the winter where they still roosted in large colonies.  Passenger pigeon roosts destroyed vast areas of the forest.  The weight of all those birds broke limbs off trees and even busted thick tree trunks in half.  The armies of pigeons vacuumed all the acorns, beechnuts, and chestnuts off the forest floor, leaving no mast for other animals.  But their dung was the most detrimental element of their roosts–overfertilizing the soil and killing all the trees in the vicinity.  Yet, ecologists believe passenger pigeons played a critical role in creating habitat diversity across the landscape.

Illustration showing how passenger pigeons created more diverse habitats.

Flocks of migrating passenger pigeons could eclipse the sun for as long as 14 hours.  Areas of the forest where they roosted were devastated.

Stuffed specimen of a male passenger pigeon.

The response of the environment following the aftermath of a cataclysmic pigeon occupation would have been interesting to study.  Unfortunately, passenger pigeons were overhunted to extinction before scientific studies of their ecological impact could be conducted.  However, we can safely assume the environment recovered in stages.  First, plants; such as ginseng, pokeberry, and Virginia creeper; that thrive in soils rich in nitrogen were the initial species to grow in the open conditions strewn with fallen dead trees and limbs.  Second, as rain reduced the concentration of nitrogen in the soil over the years; ragweed, grasses, sedges, and composites returned.  A shrubby stage with pioneer trees including cedar and pine gradually replaced the grassy stage.  Acorns carried by jays and squirrels sprouted into oaks that grew with the pioneer trees before eventually outcompeting them.  If undisturbed for centuries, shade tolerant species such as maple and beech took over from the oaks. The dead wood from the original pigeon roosts was flammable during dry weather, and wild fires were likely more common, explaining why fire-tolerant species of oaks (burr, white, and black) predominated in the Midwest.

In many areas of the Midwest some species of oaks are in decline, especially white oak, while red oak is increasing.  White oak germinates during the fall when passenger pigeons were absent in this region.  But the pigeons were able to consume spring-germinating red oak acorns after the snow melted.  Moreover, red oaks are less fire tolerant than white oaks.  Oaks are also shade-intolerant and are being replaced by shade tolerant maples.  Ecologists think white oaks are missing the passenger pigeon invasions that created the natural disturbance they need and reduced the competition they now face from red oaks.

Scientists with the Revive and Restore Project hope to genetically engineer the passenger pigeon by cutting and pasting their genes into the embryos of their closest living relative, the band-tailed pigeon.  I doubt they will successfully be able to re-establish passenger pigeons in the wild.  Passenger pigeons fail to breed unless they live in enormous colonies.  To survive predation, they must exist in large numbers…the sheer size of their population was the survival mechanism they required.  Researchers would need to release at least 10,000 birds to establish a successful breeding population in the wild.  Passenger pigeons evolved their survival strategy millions of years ago.  Though 1 genetic study suggests their overall numbers fluctuated with changes in climate phases, I am convinced they always occurred in large colonies. The task of re-establishing these numbers is probably an impossible one.

See also: https://markgelbart.wordpress.com/2010/08/27/pleistocene-passenger-pigeon-populations/

Palm Groves and Coastal Savannahs of the Pleistocene

July 28, 2016

Western Gulf coastal prairies are subtropical grasslands that were formerly widespread along the coastal plains of Texas and Lousiana.  Bluestem and Indian grasses, common components of tall grass prairies to the north, also grow here.  Near the coast and on wetter locations the coastal prairies often merge with freshwater, brackish, and salt marshes.  Drier soils host cactus, mesquite, Texas persimmon, and prickly ash.  Hurricanes and lightning-induced fires maintain these prairies where herds of bison used to graze.  Groves of Texas palms (Sabal texana) occur in the lower Rio Grande valley because the river serves as a fire break that protects this non-fire adapted species.  Palm groves grew as far as 50 miles inland during the 19th century, but now there are only 100 acres left, most notably in the Sabal Palm Sanctuary located in Cameron County, Texas.  Coastal prairies have also become rare–less than 1% of these remaining unique grasslands are considered pristine.  Most have been converted to agriculture.

Western Gulf Coastal Grasslands map.svg

Location of coastal prairies.  This environment was likely more widespread during Ice Ages when dry land extended into the Gulf of Mexico for 50 miles.

A grove of Texas palms.  Paradoxically, this environment may have been more widespread during Ice Ages.

Coastal prairie adjacent to a salt marsh in the Aransas National Wildlife refuge.

Adults

Coastal prairies support 1 of the 2 remaining populations of whooping cranes.

Palm groves and coastal prairies were likely much more widespread during Ice Ages of the Pleistocene.  Glacial advance caused the Gulf of Mexico to recede, resulting in a larger region of dry land where both environments could expand.  The prairies served as a corridor that facilitated the movement of western and South American flora and fauna into southeastern North America.  Prairie chickens, upland sandpipers, and 13-lined ground squirrels are some western species that lived in the south during the Pleistocene.  Ground sloths, glyptodonts, pampatheres (a type of giant armadillo), and mixotoxodons (a large primitive ungulate) used the corridor to advance from South America to what today are the southern United States.  The coastal grasslands supported great herds of grazers including mammoths, bison, horse, and giant tortoises.  These in turn attracted large predators such as lions, scimitar-toothed cats, and dire wolves.

Paradoxically, this region may have been warmer during the coldest stages of Ice Ages.  Glacial meltwater periodically flushed into the North Atlantic, shutting down the Gulf Stream (the tropically heated water that flows into the North Atlantic and keeps climate mild).  This caused average annual temperatures in the upper and middle parts of North America to plummet.  So this tropically heated water stayed in the Gulf of Mexico, making average annual temperatures in this region warmer than modern day temperatures.  The geographical location of the transition between the colder region of the continent and the warmer region may have been abrupt, perhaps explaining why species with northern affinities are often found associated with warm climate species in so many Pleistocene-aged fossil sites.  This transition zone likely shifted frequently, on a decadal or even annual basis. Conversely, during interstadials when the Gulf Stream restarted, the middle latitudes enjoyed warmer average annual temperatures (but not as warm as those of today), while the region adjacent to the Gulf of Mexico cooled down (perhaps cooler than modern day temperatures). Changes in the composition of flora and fauna lagged behind these sudden climatic changes.

The lower Rio Grande valley is the northern limit of many tropical species found nowhere else in the United States.  Bird watchers can find red-crowned parrots, green parakeets, brown jays, green jays, chacalacas, groove-billed anis, Altamira orioles, Aplomado falcons, and common paroques here.  These tropical species likely spread across the region during stadials when the climate was warmer, but they experienced range reduction during interstadials.

parrot

Red-crowned parrots recently colonized south Texas.  Woodpecker-excavated cavities in frost-killed palms provide perfect nesting for them.

Green Jay Photo

Green jay.

Groove-billed anis.

Possible Resurrection of the Mammoth as early as 2018

July 22, 2016

The woolly mammoth (Mammuthus primigenius) will roam the earth again and soon, thanks to new advances in genetic engineering.  The new technology is based upon another fairly recent discovery known as CRISPR, an acronym that stands for clustered interspaced short palyndromic repeats.  Scientists discovered CRISPR when they were studying how a bacteria’s immune system works.  Viruses often attack bacteria.  To develop immunity to the viral infection, the bacteria cut and paste fragments of the virus’s DNA into its own genome.  Jennifer Douda and Emmanuelle Charpentier realized they could use this process to cut and paste desired changes into an organism’s genome.  They engineered the protein CAS9–2 RNA molecules that made it easy to cut and paste characteristics of 1 species into another species genome.  Feng Chang and Georgie Church were the first scientists to use this technology on a human cell, and now there is a big patent dispute between Chang and Douda over who deserves the monetary reward for this potentially lucrative invention.  As early as 2018, George Church of Harvard University plans to cut and paste certain characteristics of the woolly mammoth into an Asian elephant (Elephas maximus) embryo that will then be implanted in an elephant.  If this project is successful, the woolly mammoth will be reborn.

Scientists recently sequenced the genomes of 3 Asian elephants and 2 woolly mammoths.  (They were able to extract DNA from woolly mammoth carcasses preserved in Siberian permafrost.)  The Asian elephant is the closest living relative of the woolly mammoth.  The study confirmed the common ancestor of both species diverged about 5 million years ago.  The genetic evidence shows since that divergence the woolly mammoth evolved many adaptations to frigid environments.  Woolly mammoths evolved thick fur, short ears, a thick layer of fat, a hump of brown fat between the shoulders, reduced sensitivity to cold, enlarged sebaceous glands, and an altered circadian rhythm response.  Sebaceous glands secrete oil into hair for lubrication.  This made woolly mammoth fur waterproof and would have helped them keep warm in wet conditions.  The altered circadian rhythms were an adaptation to the extreme changes in day length that occur in the upper northern hemisphere.  These are the woolly mammoth characteristics Georgie Church will cut and past into an Asian elephant embryo.

Eventually, woolly mammoths could populate an experimental Pleistocene Park located in Siberia.  Herds of woolly mammoths could co-mingle with caribou, moose, horses, bison, yaks, Saiga antelope, and camels.  The foraging and trampling of all these animals compacts the soil, keeping the permafrost intact.  Scientists believe this could help mitigate the effects of global warming, so there is a practical purpose for re-introducing woolly mammoths to the environment.  I know it would be a tremendous tourist attraction and hopefully some day much of Siberia will be overrun with megafauna.

Pleistocene park photos

View of the experimental Pleistocene Park in Siberia.  The re-introduction of horses has increased the grassland cover here.

References:

Lynch, Vincent; et. al.

“Elephantid Genomes Reveal the Molecular Bases of Woolly Mammoth Adaptation to the Arctic”

Cell Reports 2015

Woolly Mammoth Revival

Specimen #USNM 437648

July 17, 2016

I was confused about the Harleyville Giant Cement Quarry fossil site for many years.  Some of the scientific literature reported the fossils found there were over 300,000 years old, while other papers gave them an approximate age of 20,000 years BP.  Finally, someone sent me a message, clearing up my confusion.  These are 2 different fossil sites–both in Dorchester County, South Carolina but several miles apart.  In 1989 Roy Ogilvie, an amateur fossil collector, found a nearly complete dire wolf skull at the site with the 20,000 year old bones.  This specimen is now stored at the U.S. National Museum and was given the number 437648.  It is the only dire wolf (Canis dirus) skull ever found in South Carolina, though several isolated teeth have been recovered from other sites.

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Photo of specimen #USNM 437648 from the below referenced book.  It’s nearly complete, missing just a few teeth.

The size of this skull is remarkable.  Ronald Nowak, a renowned fossil canid expert, measured 62 dire wolf skulls that were excavated from the La brea Tar Pits in California.  #USNM 437648 is larger than all of them.  It may just be coincidence, but perhaps eastern dire wolves were on average larger than their western counterparts.  In any case this was a big wolf.  However, it is not the largest dire wolf skull known.  A dire wolf skull from south Texas and another from the Maricopa tar seeps in California were slightly larger than this specimen.

The associated faunal remains, known as the Ardis local fauna, suggest #USNM 437648 lived in a mostly wooded habitat with some grassy openings and aquatic habitats.  Tapir, white-tailed deer, stout-legged llama, long-nosed peccary, woodrat, beaver, gray squirrel, flying squirrel, jaguar, Florida spectacled bear, and Jefferson’s ground sloth all are (or were) denizens of woodlands or even deep forest.  Mastodon, beaver, and river otter indicate wetland habitat.  Bison, horse, mammoth, meadow vole, hog-nosed skunk, 13-lined ground squirrel, and pampathere show that grassland environments existed here as well.  Dire wolves were a generalist species.  Specimen #437648 likely hunted in all 3 habitats.

Reference:

Sanders, Albert

Additions to the Pleistocene Mammal Faunas of South Carolina, North Carolina, and Georgia

American Philosophical Society 2002

Extinct Subspecies of Pleistocene Jaguars (Panthera onca)

July 12, 2016

The ancestor of the jaguar diverged from ancestral lions and leopards about 8 million years ago.  An extinct species of jaguar (Panthera gombaszoegensis) roamed Eurasia from the early to mid Pleistocene (1.5 million years BP- ~300,000 BP).  This species crossed the Bering Land Bridge over 500,000 years ago and colonized North and South America where it evolved into Panthera onca–the same species still found today from Arizona to Argentina. The jaguar had a much wider range in North America during the late Pleistocene than it does now.  Jaguar bones, dating to this era, have been excavated from sites as far north as Washington state, Oregon, Indiana, West Virginia, and Pennsylvania.  I’ve reviewed the data from these sites in an attempt to determine when jaguars ranged this far north.  I was curious to know if jaguars were able to survive that far north during the coldest climatic phases.  However, these sites are all cave deposits without reliable dating evidence.  Associated faunal remains may be from specimens thousands of years older or younger than the jaguar remains and because climate often fluctuated rapidly during the Pleistocene, they can’t be used as an index for the climatic conditions that occurred when the jaguars lived in the regions.  The ancestor of Panthera onca did negotiate the Bering Land Bridge and Canada to reach its known Pleistocene range.  This region was quite cold even during warmer climate phases, so I believe Pleistocene jaguars were more adaptable to climatic extremes than one might expect.  There’s just not enough evidence to know for sure.

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Both extinct subspecies of Pleistocene jaguars were somewhat larger than present day jaguars.

Pleistocene jaguars were abundant in southeastern North America, rivaling dire wolves (Canis dirus) as the most common large predator in the region then.  Jaguars have been unearthed from at least 18 sites in Florida, 6 sites in Tennessee, 2 sites in Georgia, 1 in South Carolina and another in Alabama.  A jaguar fell into Craighead Caverns in Tennessee and even left paw prints and claw marks in its failed attempt to escape the natural trap.  Complete skeletons of jaguars have been found in other Tennessee caves.  The jaguar that lived in the southeast during the Pleistocene was a distinct subspecies known as Panthera onca augusta.  It was given subspecies status based on its size, averaging 15%-20% larger than the modern jaguar.  Extant jaguars still demonstrate clines (geographical variations in size).  Present day jaguars average larger in the northern and southern limits of their range than they do near the equator.  Larger individuals maintain body heat more efficiently, perhaps explaining the size difference in the cooler parts of their range.  Present day jaguars also grow larger in areas where they can prey on livestock.  So it’s likely the combination of cooler climate and larger prey contributed to the larger size of P. onca augusta during the Pleistocene.

Another extinct subspecies of jaguar lived in South America–P. onca mesembrina.  This population of jaguars also averaged larger than present day jaguars.  A study of P. onca mesembrina genetics determined this clade became extinct in southern Argentina about 12,280 calendar years ago along with other regional megafauna including Darwin’s ground sloth, horse, a llama (Lama gracilis), and a local population of guanacos(Lama guanacoe).  These clades of jaguars and guanacos left no descendents, but other clades of these species recolonized southern Argentina less than 2,000 years later.  The scientists who participated in this study conclude human activities combined with a warming climate phase caused megafauna extinctions here.  Southern beech forests expanded as temperatures and precipitation increased, and the forest encroached on the grasslands.  Herds of grazing animals, forced to migrate greater distances to reach suitable pastures, were more easily ambushed by an increasing human population that now had access to more wild plant foods in the growing forests.  Megafauna survived previous climate changes by altering their patterns of movement throughout the landscape, but some how humans disrupted this during the terminal Pleistocene.

References:

Metcalf, Jessica; et. al.

“Synergistic Role of Climate Warming and Human Occupation in Patagonian Megafaunal Extinctions during the Last Deglaciation”

Science Advances June 2016

Simpson, G.G.

“Discovery of Jaguar Bones and Footprints in a Cave in Tennessee”

American Museum Novitates 1941


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