Archive for March, 2013

The Spectacular Narrows Flood of 13,350 BP

March 29, 2013

A few bands of Paleo-Indians probably roamed the Georgia coast about 13,350 years ago.  The shoreline then may have been as much as 50 miles east of where it is today because much of earth’s water was locked in glaciers and glacial lakes.  The climate here was pleasant–brief mild winters and long warm summers that didn’t often reach the maximum temperatures of today.  Paleo-Indians living along the coast enjoyed a varied diet of fish, shellfish, turtles, sea birds, sea mammals, as well as big game and wild plant foods.  One summer day, a group of Paleo-Indians spear-fishing, netting, and swimming in the shallow coastal waters may have noticed that the water was much chillier than normal.  The water may have gotten so cold, they decided to stop fishing and swimming.  But they didn’t need to spearfish, the sudden change in temperature stunned and killed millions of fish which suddenly washed ashore, providing more food than they could eat.  The Paleo-Indians living here had no idea why the water suddenly turned cold on a warm summer day, but an Indian standing on a bluff overlooking what is now New York Harbor might have figured it out.

18,000 years ago, the Laurentide Glacier reached its maximum extent, and it towered a mile over what today is the Manhattan skyline.  As it expanded, it pushed dirt and boulders forward forming a long hill known as a moraine.  The glacier buried and froze most of the Hudson River, however, it did not reach the Atlantic Ocean.  Instead, a narrow strip of land existed between the massive glacier and the Atlantic Ocean.  This strip of land likely consisted of a mosaic of grassy steppe, spruce forests, and wetlands and was inhabited by mammoth, horse, bison, and near the coast seal and walrus.  The part of the Hudson River not under ice cut a valley through here.

Canebreaks 008

Map of the submerged Hudson River valley incised when the land here was above sea level during the Ice Age.  The continental shelf was dry land habitat then.  Map from the below referenced paper authored by Robert Theiler and others.

Manhattan skyline.  Note how some buildings are much shorter than others.  This is not perchance.  The tall ones are located on top of hard Paleozoic aged rock.  The short ones are located on softer Pleistocene sediments.  Taller buildings couldn’t stand on the softer, younger sediments without falling over.

Climate warmed and the Laurentide Glacier began to retreat.  But it left behind the Harbor Hill moraine which formed a natural dam across Long Island and Staten Island.  This dam created several glacial lakes.  Lake Passaic covered much of what today is northern New Jersey, and its depth was astounding, ranging from 150-240 feet.

The Narrows–the entrance to New York Harbor.  And the Verazzano Bridge which connects Long Island with Staten Island.  A moraine once blocked this exit acting as a dam which formed several glacial lakes.

Map of the glacial lakes formed by the Harbor Hill Moraine.  The gray area represents dry land that was inundated when the moraine was breached by meltwater.

Further upstream on the Hudson River, ice dams formed 3 major glacial meltwater lakes–Lakes Iroquois, Vermont, and Albany.  Summers kept getting longer and wamer until ~13,350 years BP when the ice dam forming Lake Iroquois collapsed, releasing a torrent of freshwater that carried chunks of ice, whole trees, big boulders, and any wildlife unable to scramble out of the way.  This tremendous flood scoured the Hudson River Valley, exposing rock outcroppings still visible today.  The flood smashed through the Harbor Hill moraine, obliterating the part of the hill that had connected Long Island with Staten Island.  The Hudson River surged through its old valley to the sea where the massive influx of cold freshwater shut down thermohaline circulation–the ocean current that moderated much of Europe’s and eastern North America’s climate.  This led to a sudden drop in average annual temperatures from north Florida to Canada and precipitated the Younger Dryas cold snap which equaled temperatures endured during the Last Glacial Maximum.  (Temperatures from south Florida to the equator rose because tropically warmed ocean water stayed there instead of circulating north.)

Observed from a safe distance, the natural cataclysm that created the narrows entrance to New York Harbor must have been an awe-inspiring sight.  It’s a shame video cameras hadn’t been invented yet.  Nothing like this flood has occurred within recorded history.  Evidence is found strewn all over the bottom of New York Harbor which became the resting spot for tons of sediment, boulders (dropstones), trees, and animal bones that fishermen occasionally dredge up.

Most of the Harbor Hill Moraine is still intact and can be found on Long Island and in New Jersey.  Only the part that went across the narrows was breached and destroyed.

The Paleo-Indians living on the coast of Georgia then were soon forced inland as rising sea levels inundated their favorite beaches.  They had no way of knowing the rising sea was tied to the unusually cold water they felt on a summer day a few months earlier.

References:

Merguerian, Charles

“The Narrows Flood–Post Woodfordian Meltwater Breach of the Narrows Channel, NYC”

http://www.geo.sunysb.edu/lig/Conferences/abstracts-03/merguerian-03.pdf

Thieler, Robert; et. al.

“A Catastrophic Meltwater Flood Event and the Formation of the Hudson Shelf Valley”

Paleogeography, Paleoclimatology, and Paleoecology (241) 2007

Advertisements

Pleistocene Fossils Found on the Georgia Bight

March 25, 2013

Geologists refer to the continental shelf off the Georgia coast as the South Atlantic Bight.  It’s a bend of the continental shelf that stretches from off the North Carolina shore to Cape Canaveral, Florida.  Today, the South Atlantic Bight (SAB) is inundated with sea water, but over the past 2 million years much of it has been above sea level during at least 10 different Ice Ages.  Most recently, the SAB has emerged above sea level from ~38,000 BP-~8,000 BP.  Fossils and pollen from about this time span accumulated near 2 now underwater structures studied by scientists: Gray’s Reef and J Reef.  Both structures are about 60 feet underwater.

Map of Gray’s Reef and J Reef.  Gray’s Reef is a natural sandstone outcropping.  J Reef is composed mostly of scallop shells.  Between 38,000 BP-8,000 BP both were near sea level during interstadials and well above sea level during stadials.  J Reef was inundated by sudden rising sea levels ~8,000 BP about the same time Glacial Lake Agassiz in Canada suddenly drained when an ice dam melted.  The sudden inundation prevented speedy erosion of the reef.

Canebreaks 007

Maps of the Georgia Bight and the location of J Reef and Gray’s Reef during 2 different time periods.  Top:  from 45,000 BP when both sites were at or near the coast.  This is an interstadial period. Bottom: from 13,000 BP when both sites were well above sea level.  Click to enlarge.  Map is from the below reference authored by Ervan Garrison and others.

Gray’s Reef is a dolomitic sandstone outcropping, originating 2-3 million years ago.  Buried sand and seashells became cemented together, then erosion exposed the rock.  Gray’s Reef has been a protected marine sanctuary administered by NOAA since 1981.  It’s located 16 miles east of Sapelo Island and is 22 square miles in extent.  Scientists took cores of sediment from numerous locations within Gray’s Reef, and they analyzed and dated the pollen.

J Reef, 8 miles north of Gray’s Reef, is composed of an entirely different structure.  It’s a shell bed adjacent to a submerged river valley, perhaps a former bluff.  This ledge acted as an impediment that accumulated seashells and bones carried by ocean currents.  Over time, the seashells became cemented together in a lag deposit.  Shells of the giant scallop (Placopecten magellanicus) dominate the lag deposit.  This cold water species no longer occurs south of offshore North Carolina.  The scallop shells that form J Reef date to between ~40,000 BP-~32,000 BP when this area was close or right on the shoreline.  The abundant presence of the giant scallop is evidence the ocean waters off the Georgia coast during this time period were cooler on average than they are today.  In recent decades humans dropped so much junk on the ledge to attract fish that some scientists refer to it as an artificial reef.

I think both of these are shells of the giant scallop (Placopecten magellanicus).  The one on the left turned gray because it has been dead for awhile. Giant scallops are the primary shell that composes J Reef off the Georgia coast.  Today, this species occurs off the continental shelf from Canada to North Carolina.  Between 45,000 BP and 8,000 BP this species lived near inshore waters off the Georgia coast which extended many miles east from where it is today.  The presence of this cold water species suggests cooler waters were prevalent off Georgia’s coast during the Ice Age.

Photo of a live scallop.  Fresh scallops are very delicious.  Frozen scallops sold in mass market grocery stores are treated with preservatives that make them taste terrible.

Scuba divers found the lower jaw bone of a gray whale (Estrichius robustus) embedded in the scallop shell bed, and with difficulty they extracted it a few years ago.  It dates to 36,000 BP, making it the oldest gray whale fossil on the American side of the Atlantic.  (Older specimens have been found off the coast of Europe, Japan, and California–some dating to the Pliocene.)  Whalers hunted gray whales to extinction in the Atlantic by 1695, but they are making a comeback in the Pacific.  Gray whales are spectacular animals, weighing 36 tons (that’s 72,000 pounds!), growing to 45 feet long, and living up to 60 years old.  They used to be called the “devilfish” because they aggressively attacked whalers when they were hunted.  Gray whales use their lower jaws to scrape through bottom sediment.  The baleen in their mouth filters food from the mud, including small crustaceans (mostly amphipods), plankton, squid, and fish.  They use their tongues to dislodge the food from their baleen before swallowing.  They fatten on these organisms, developing a 10 inch layer of blubber that provides sustenence for 3-5 months because they seldom feed in warmer waters where they breed and give birth.  Usually, gray whales are covered in barnacles and whale lice.  Fossils of the still abundant bottlenose dolphin (Tursiops truncatus) have also been found in the shell bed.

36,000 year old gray whale mandible found embedded in J Reef.  It was excavated with difficulty by teams of scuba divers.  Whalers extirpated gray whales from the Atlantic Ocean by 1695.  This is the oldest fossil specimen of this species found on this side of the Atlantic.

Gray whale surrounded by seals.  A live specimen is always more impressive than a fossil.

Scuba divers are finding land mammal fossils in the paleochannel next to J Reef as well.  When the site was above sea level, mammal fossils washed into the river, and now that it’s submerged, they can be found without the need to dredge or remove vegetation.  So far, over 100 specimens have been recovered, though most are disarticulated and fragmentary.  Mammoth, bison, horse, and llama fossils have been brought to the surface by scuba divers.  Scientists have yet to publish a paper detailing the finds.  Local news outlets incorrectly reported a mammoth rib as belonging to a woolly mammoth,  I doubt woolly mammoths ranged this far south.  Instead, the rib is more likely from a Columbian mammoth which ranged throughout the continent.

Archaeologists found a projectile point, an antler/bone tool, and 2 other stone artifacts near J Reef.  The lithic design is classified as archaic Indian, a culture that dates to between 8,000 BP-5,000 BP.  Sea level suddenly rose 12 feet here about 8,000 years ago, inundating Gray’s and J Reef.  This preserved J Reef from rapid erosion, though ocean currents are gradually eating it away.  The massive flood originated from the collapse of an ice dam that created an enormous glacial lake in Canada.  This event is probably the basis for many worldwide flood myths.

A few pieces of fossil wood in cored sediments surprised scientists who were expecting to find just pollen.  They identified red cedar, beech, and pepperleaf sweetwood (Licaria triandea); all dating to about 41,000 BP.  The former 2 still occur on the South Atlantic coastal plain, but pepperleaf sweetwood is restricted to 2 areas within the city limits of Miami, Florida as well as Puerto Rico and South America.  Pepperleaf sweetwood is a tropical plant in the bay family.  It probably ranged on a narrow strip along the coast which remained relatively frost free until the Last Glacial Maximum.  It may have been a relic from an Interglacial expansion that occurred when climate was warmer than that of today.  At one time it may have been widespread throughout the south, but as the Ice Age advanced, its range gradually became more restricted until the climate got too cold, even on the coast.

Evergreen scrub with wax myrtle and pepperleaf sweetwood grew on high dunes behind beaches about 41,000 BP along the Georgia coast, and that habitat probably looked much like this photo.  Pepperleaf sweetwood is a tropical plant that has not yet recolonized the southeast since the Last Glacial Maximum when it became extirpated in the region.  If the planet continues to warm, it may grow here once again.

Pollen evidence from Gray’s Reef sediment cores paint a picture of a dynamic landscape sculpted by frequent fire, sudden dramatic climate changes, and megafauna foraging.  Fire adapted species such as pine, oak, grass, herbs, ragweed, and ferns predominated.  The South Atlantic Coastal plain consisted of a mixture of woodland, grassland, and wetland. The period known as MIS 3 (60,000 BP-25,000 BP) is noted for having highly unstable climate as Ice Age glaciers alternatedly waxed and waned.  Scientists have discerned 5 major changes in floral composition during this stage, and they correlate with Heinrich events–the sudden release of melted glacial water into the north Atlantic that shut down thermohaline circulation and caused average annual temperatures to plummet.  Within MIS 3 average annual temperatures increased during warm swings and decreased during cold swings by as much as 14-28 degrees Fahrenheit in less than a decade, stressing plant and animal life alike.  During cold stages pine increased at the expense of oak because pine is better adapted to wind, drought, and lower levels of CO2.  During warm stages oak increased while pine decreased because under these conditions they shade out conifers.  Up until about 29,000 BP forests on the South Atlantic coastal plain remained diverse with birch, beech, chestnut, and even hemlock growing with pine and oak.  But conditions deteriorated, and South Atlantic forests became species poor, dominated completely by pine and oak.  The forests remained of low diversity until about 15,000 BP when climatic conditions improved.

References:

Garrison, Ervan; et. al.

“Late Quaternary Paleoecology and Heinrich Events at Gray’s Reef National Marine Sanctuary, SAB, Ga.”

Southeastern Geology 48 (4) Feb 2012

http://graysreef.noaa.gov/science/publications/pdfs/garrison_et_al_segeo_feb2012.pdf

Noakes, Scot; Ervan Garrison, and Greg McFall

“Underwater Paleontology: Recovery of a Prehistoric Whale Mandible Offshore Georgia”

Diving for Science 2009

http://graysreef.noaa.gov/science/publications/pdfs/i-25.pdf

Mighty Mouse

March 21, 2013

Imagine a 100 pound tarantula.  Now imagine an unarmed man attacking the giant tarantula in a fight to the death.  A 100 pound tarantula would quickly kill the best human fighter, even the heavyweight ultimate fighting champion, in seconds.  A human would be unable to grip the stinging hairs on the arthropod’s legs, and the spider would immediately paralyze a human with its venomous fangs.  So the grasshopper mouse (Onchomys leucogaster) deserves our respect because they regularly bite and punch tarantulas and scorpions into submission as the link to the following video shows.  Note the victory roar, or I should say squeal.

http://www.youtube.com/watch?v=qyQGByV3aFU

Grasshopper mouse.

Mice are thought of as timid animals.  Not so, the grasshopper mouse.  They often tackle and subdue large insects, such as grasshoppers (hence the name).  They also defeat and consume tarantulas, scorpions, lizards, and other mice.  In captivity they’ve been known to kill cotton rats 3 times their size.  They win confrontations with other rodents by biting through the skull.  Grasshopper mice are immune to scorpion and spider venom, explaining how they can battle them with no ill effects.  Meat makes up 90% of their diet, while vegetal matter forms the balance.  This is the opposite diet ratio of their closest relatives–mice of the peromyscus genus.  Scientists believe the 2 species of grasshopper mice diverged from the peromyscus genus during the Miocene.  Grasshopper mice occupy the same ecological niche as the European hedgehog, but they prefer more arid conditions and are often found associated with prairie dog towns.

During the Pleistocene grasshopper mice extended their range at least partially into southeastern North America.  Fossil specimens of grasshopper mice were unearthed at Peccary Cave, Arkansas.

Modern range map of the more widespread species of grasshopper mouse (Onchomys leucogaster).  During the Pleistocene the ranged farther east, at least to Arkansas.

Though there’s no evidence grasshopper mice ever ranged into Georgia, 5 species of the peromyscus genus do live in state.  Deer mice (Peromyscus maniculata) live in the extreme northern mountains of the state.  The white-tailed mouse or wood mouse (P. leucopus) lives in wooded areas throughout the state.  The cotton mouse (P. gossypinus) lives in fields all over the state.  The cotton mouse looks like a white-footed mouse but is larger and has a longer skull.  The old field mouse (P. polionatus)  lives in fields and beach dunes and is also known as the beach mouse.   The attractive golden mouse (P. nuttalli) is restricted to brushy areas covered by vines.  They construct nests in bushes and use vines to travel within their territory.

Old Field Mouse (P. polionatus)

White-footed mouse (P. leucopus)  The cotton mouse looks similar but is longer.

Golden mouse (P. nuttalli)

Fossil evidence from the peromyscus genus has been found at several fossil sites in Georgia, but unless the material includes skulls, scientists can’t determine which species they belong to.  Curiously, my cats have never brought me a specimen of peromyscus, and I conclude they are scarce or absent in my neighborhood.  Mice and voles in general are not common near my house.  The only species of mouse I ever witnessed as a victim of my cats is the non-native house mouse (Mus musculus), and that was just twice.  It may be the cats eat mice before I see them.  Other small mammals my cats have killed include short-tailed shrews, eastern moles, a star-nosed mole, a baby possum, squirrels, rabbits, and I think a pocket gopher.

The Biogeographical History of the Prickly Pear Cactus (Opuntia sp.)

March 18, 2013

Prickly pear fruit tastes like watermelon but with an even higher ratio of seed to fruit.  They ripen about mid-fall and hang on  the cactus pads through winter when consequently, they often taste like overripe mushy watermelon.  They are high in Vitamin C and anti-oxidants and provide much food energy for humans and wildlife.  I pick them with tongs and use a paring knife to remove the skin and the attached, irritating spines, known as glochids, that don’t seem to stop any creature from eating them.  The prickly pear genus originated in South America, and the seeds, carried in the guts of small and large animals, were transported to North America when a landbridge formed between the 2 continents about 3 million years ago.  Humans have planted them in Africa and Australia where they’ve become an environmentally harmful invasive species.

Opuntia humifusa (eastern prickly pear) in flower.  This species ranges from Florida to eastern Canada.

Eastern prickly pear fruit.  It tastes like watermelon.  During the growing season this species grows upright, but during winter it grows flat on the ground.  The fruit of various species of opuntia can be red, purple, yellow, or even white.

Cactus patches like this are common in Texas.  Texas was a gateway for Opuntia into North America.  Javelina and wild hog spread Opuntia seeds in their dung, and the cactus grows in patches.

During the Pleistocene many Opuntia species evolved to become resistant to frost.  Prickly pear cactus thrives on poor sandy soils because they can retain water better than most other plants.  This would have made them especially well adapted to southeastern North America during arid stadials when sandstorms smothered many square miles of territory.

61 species of prickly pear live in North America today.  Texas hosts the most species–20, while 7 frost sensitive species are endemic or almost endemic to Florida.  An additional 7 species are found throughout the southeast.  2 species are cold tolerant enough to live in Canada.  A study of prickly pear DNA determined that southeastern and southwestern regions of North America provided refuges for prickly pear cactus during the Last Glacial Maximum.  When prickly pear cactus recolonized the midwest and Canada after the retreat of the glacier, closely related species came into conact with each other and hybridized.  This suggests that many more species of Opuntia may be the result of hybridization events that occurred when isolated populations reunited after thousands of years of separation due to climate-initiated environmental changes.  The commercially grown Opuntia ficus-indica is itself a manmade hybrid originally cultivated in Mexico.  Its exact parentage is unknown.  It has been bred to produce large spineless fruit called “tunas.”  I tried growing this cultivated variety from seed I extracted from store-bought fruit, but none germinated.  However, I do have a cactus in a pot that I grew from seed I got from a local wild species–Opuntia humifusa.  This species is quite common in my neighborhood because the soil here consists of Eocene-age sands.

Prickly pear cactus flowers attract all kinds of insect pollinators such as bees, wasps, butterflies, and flies.  Peccaries, deer, ground squirrels, rabbits, skunks, coyotes, foxes, turkeys, box turtles, and gopher tortoises all eat the fruit and spread the seeds in their dung.  Much of Texas’s landscape is covered with cactus patches, probably borne from javelina feces.  Pleistocene megafauna must have created cactus patches across much of the south, especially during dry climate stages when Opuntia was a dominant plant.

Collared peccary (Pecari tagaeu) eating a prickly pear cactus pad.  I thought I’d make it 3 blog entries in a row with something about peccaries by writing an essay about their favorite food.

The cactus pads are also edible, and herbivores sometimes forage on them, but to a lesser degree.  There is less food value in the pads, and the penalty of dealing with spines discourages animals from chewing them down to the root.  Opuntia bugs (Chelindrea sp.), though, plague cactus.  They suck the juice from the pads and can kill the cactus.  Last summer, I thought Opuntia bugs killed the prickly pear cactus I’m growing in a pot, but that tough old cactus did grow back from the roots this winter when the cold weather wiped out their nemesis.

Opuntia bugs (Chelindrea sp.) engaging in sexual intercourse.  There are about as many species of Opuntia bugs as there are of cactus.  They look like squash bugs–the scourge of gardeners.

Reference:

Majore, L.C.; W.S. Judd; P.S. Soltis, and D.E. Soltis

“Cytogeography of the humifusa clad of Opuntia (Cactacaea, Opuntiodoene, Opuntaeae) Correlations with Pleistocene Refugia and Morphological Traits in Polypoid Complex”

Comparative Cytogenetics 60 2012

Save the Rio Aripauna Ecosystem

March 13, 2013

The rain forests of Brazil are well known for their biodiversity, but the Rio Aripuana basin is especially rich in species.  (The Rio Aripuana is a tributary of the Rio Madeira which in turn is a tributary of the Amazon River.) At least 181 species of mammals (half of which are bats), and over 600 species of birds live in this region.  The Amazon River basin hosts an astounding 750 species of fish.

Location of the Rio Aripuana.  The satellite photo is of an island in the middle of the river where a new species of plant was found.

Photo of Rio Aripuana shoreline.  The Rio Aripuana ecosystem includes closed canopy forests, seasonally flooded forests, savannah woodlands, and an environment local scientists refer to as white sand savannah.  This region was geographically isolated from the rest of South America for over a million years resulting in numerous examples of speciation.

The Rio Aripuana basin has a geological history of shifting river systems and lakes.  A massive prehistoric lake and a network of white water rivers cut off the Rio Aripuana region from the rest of South America about 1.2 million years ago.  The resulting isolation caused many ancestral populations of mammals to evolve into new species.  Less than 10,000 years ago, the Madeira River changed course and became a tributary of the Amazon River causing a drainage of the prehistoric lake into the mighty outlet.  The former lake bed became the Tenharim Savannah which proved to be no barrier to wildlife.  Common mammals from elsewhere on the continent colonized the dry savannah woodlands adjacent to the Rio Aripuana basin.  Many of the colonizing species are in the process of outcompeting the endemic species that evolved here in isolation.  The region is a living laboratory of evolution.

The biogeographical history of the Rio Aripuana ecosystem explains why there are so many different species of closely related mammals here.  Within the last 15 years Marc van Roosmalen, a world renowned primatologist, has identified 12 species new to science, and he claims there are an additional 18 more, but not enough information is known yet to designate them as accepted new species.  I should note that some scientists are doubtful about the true status of many of these species, and they believe some merely deserve subspecies status.  Genetic studies of new species of peccary and brocket deer suggest they split from their closest living kin 1.2 million years ago–the approximate time that the region became isolated.  Some scientists disagree with this interpetation, however.  The new species accepted by most scientists include 4 kinds of marmosets, 3 of titi monkeys, the giant peccary (Peccari maximus), a dwarf porcupine, a dwarf manatee, a dwarf tapir, the fair brocket deer, and a new species of Brazil nut.  Dr. Roosmalen also believes there are at least 13 additional species of monkeys, a tree-climbing giant anteater, a black giant otter, an orange coatimundi, and most excitingly, a large species of black jaguar with a white throat–all possibly new to science.  Species of birds, large-fruited plants, and mussels, all unknown to science, are thought to occur here too.

Photo of the giant peccary.  Genetic studies suggest it split from collared peccaries about 1.2 million years ago.  It is on average 33% larger than a collared peccary and doesn’t root as much for its food.  Canines show less wear.  Collared peccaries and white-lipped peccaries colonized the region within the last 10,000 years and co-exist with the giant peccary.  Dr. Roosmalen believes 2 additional species of peccaries new to science also live here, but not enough evidence has been found to designate them as new species. Some scientists aren’t convinced the giant peccary is a unique species, and think it’s merely a large subspecies of collared peccary.

Prince Bernhard’s titi monkey (Callicebus bernhardii).  Dr. Roosmalen named some of his new species after generous benefactors.  Officials in the Brazilian government did not like this at all.

Dwarf manatee (Trichesus pygmaeus).  They evolved to a smaller size because the waterway where they became isolated  provided less food than the region their ancestors lived in prior to 1.2 million years ago.

Amazon pink dolphin (Inia geoffrensis).  This fascinating species has a flexible neck and a long snout built to help them navigate through flooded forests and extract fish hiding in holes.  Only the males are pink.  The pink color is scar tissue from fights between males over mating rights.  Ignorant fishermen kill them for catfish bait.  Freshwater dolphins have evolved independently in 4 different regions in the world–a great example of convergent evolution.  Sadly, the Chinese freshwater dolphin is now extinct due to pollution.  China is an environmental apocalypse.

This skull of a  big cat is the only scientific evidence of the black white-throated jaguar.  It’s canines are larger than the species of jaguar known to science.  The natives know it literally (in translation) as the black- white-throated cat-that-is-bigger-than-a-jaguar-and-hunts-in-pairs.   They hunt in pairs and recently a pair killed a 9 year old girl.

Presently, the Rio Aripuana region is officially considered a “sustainable development reserve.”  This means that some areas are protected, but logging, gold and gravel mining, cattle ranching, and soybean and sugar cane monoculture are allowed.  Dr. Roosmalen believes the area is deserving of full protection under National Park status.  The Brazilian government is about as progressive when it comes to environmental issues as the United States, perhaps more so.  Brazil has slowed the rate of deforestation, and they have strict rules for hydroelectric projects.  When rivers are dammed, they are designed not to flood large areas with reservoirs, and fish ladders are constructed to help migratory species reach their ancient spawning grounds.  On the other hand the Brazilian government oppresses scientific research with ridiculous regulations, and protected areas are underpoliced.  Reportedly, they only employ 5 botanists…for the entire Amazon!  Squatters destroy about as much land as government-approved, corporate-owned projects.

Much of accessible Brazil probably looks like this.  The government protects forests on hillsides and the land immediately adjacent to the hills.  Land is cleared for cattle ranching and sugar cane or soybean fields near roads.  This is good for animals that thrive in fragmented habitat.  But it’s not enough land for some species of monkeys which will eventually die out from inbreeding.

The Rio Aripuana region has survived partial development in the past.  Some of the richest soils in the area have an anthropogenic origin.  Indians enriched the acidic forest soils with a combination of compost, charcoal, and ground mussel shells. These sophisticated agricultural practices made them successful farmers. Much of the wilderness actually grew back after European diseases decimated the Indian civilizations here.  This land is resilient.  Hopefully, the Brazilian government will do more to protect this unique ecosystem where there seems to be at least 2 of a kind of everything.

References:

http://www.marcvanroosmalen.org/

http://data.iucn.org/themes/ssc/sgs/pphsg/Suiform%20soundings/Newsletter%207%282%29.pdf

When Sand Dunes Buried Herds of Flat-headed Peccaries

March 10, 2013

Peccaries, also known as javelinas, are ungulates in the order artiodactyl.  They are classified in the suborder Suina which includes 3 families–Tayassuidae (peccaries), Suidae (true pigs), and Hippopotamidae (hippos).  Two now extinct species of peccaries were common in North America during the Pleistocene.  Fossils of the long-nosed peccary (Mylohyus nasatus) have been recorded from Florida north to New York and west to California.  This species was the size and shape of a white-tail deer.  Fossils of the flat-headed peccary (Platygonus compressus) have been found from Florida north to New York and west to California and even the Yukon.  During warm interglacials the still extant collared peccary (Peccari tagaeu) ranged into Florida and probably the coastal plain of other southeastern states.

Illustration of flat-headed peccary (on the left) and long-nosed peccary (on the right).  The size in this illustration is misleading.  Long-nosed peccaries had longer legs, but flat-headed peccaries were generally twice as heavy.  A study of 4 individual flat-headed peccary skeletons estimated they ranged in weight from 260-360 pounds.  An average long-nosed peccary usually weighed in at 150 pounds.

Because the ranges of the 2 common species of Pleistocene peccaries overlapped so extensively, and both species are often found in the same fossil sites, scientists have long proposed a difference in habitat preference between them.  However, to the best of my knowledge, there are no in depth studies examining this interesting ecological differernce.  After reviewing the available literature, I’ve reached what I believe is an orginal hypothesis of sorts:  Populations of flat-headed peccaries increased during stadials and decreased during interstadials, while the opposite is true for long-nosed peccaries.  My reasoning is based on evidence discussed below.

1. Flat-headed peccaries were an Ice Age mammal well adapted to cold, dry, and dusty environments.  An anatomical characteristic within their snout helped them breathe in an environment where sandstorms were frequent.  Their fossil remains are often found in herds that died when they were buried by windblown silt, known as loess.  Fossilized herds of flat-headed peccaries buried by loess and/or eolian sand have been found in Kentucky, Colorado, Kansas, Michigan, 2 sites in New York, and 3 sites in Ohio.  The site in Hickman, Kentucky is located in the extreme southeastern corner of the state not far from the Mississippi River.  During stadials, which were particularly cold stages of the Ice Ages, much of earth’s moisture became locked in glacial ice, fostering arid climate.  Rivers shrank in size, exposing mounds of sand and sediment.  Frequent cold winds blew this sand away from the rivers, creating great dunes.  Herds of peccaries often sought shelter from winter winds and gathered beneath overhanging loess deposits on the eastern side of the dune.  The sand dunes did provide protection from this westerly wind, but unfortunately for the peccaries, on occasion the wind caused the top part of the dune to slump on top of the poor beasts, burying them until their accidental discovery by humans some 20,000 years later.  In another scenario the herd of peccaries might get trapped on the western side of the bluff in a sandstorm and become buried because the bluff acted as a barrier that allowed the sand to pile up and over the herd. That so many fossil herds of peccaries have been found in these situations is evidence they were common during stadials when eolian dunes rolled across the landscape.

Platygonus compressus skeleton.  Herds of flat-headed peccary skeletons have been found buried in sand at 9 or more sites.

2.  The Chacoan peccary (Catagonus wagneri) was discovered as a fossil in 1931, then as a living species in 1970.  It’s considered a very close relative of the flat-headed peccary, and it probably inhabits a similar environment that would have been favored by its Ice Age cousin.  The last 3000 Chacoan peccaries live in impenetrable thorny forests.  Not coincidentally, arid climatic conditions of stadials meant the frequency of thunderstorms was greaty reduced.  Without thunderstorms, lightning-ignited wildfires were rare.  Without fire, thorny scrub forests predominated over many square miles.  Large herds of aggressive peccaries making a defensive stand in thick brush must have been difficult for predators to subdue.  That’s not to say, thorny scrub forest was the only type of environment on the landscape.  Grasslands and pine and spruce forests still existed, but scrubby growth covered a greater extent of the landscape than it did during interstadials, and this type of vegetation made a happy home for flat-headed peccaries.

A Chacoan peccary.  It’s very closely related to the extinct flat-headed peccary. It’s favorite habitat is impenetrable scrub thorn forests.  Scrub forests were common in North America during stadials because lightning-ignited wildfires were rare.  Like its living relative, flat-headed peccaries probably loved living in thickets where herds of them could make defensive stands against large predators.

Chaco, Argentina. Photograph by WWF/ Claudio Blanco

A Chacoan scrub thorn forest.  Parts of North America may have looked something like this during Ice Age summers because the climate was dry and fire was rare.  Without thermal pruning forests and grasslands can become brushy like this.

By contrast, long-nosed peccaries were a slender animal built for running through open woodland.  They survived during stadials in relic habitats where open forests still remained.  Their favored habitat expanded during interstadials and interglacials when glaciers melted and released moisture into the atmosphere spawning lightning-induced fires that burned through scrubland, clearing it and creating open woodlands.  During interstadials long-nosed peccaries were the common javelinas while flat-headed peccaries were reduced to relic status, finding suitable habitat mostly on sandy soils with sparse vegetation where fires were absent and scrubby plant growth prevailed.

Reference:

Finch, Warren; Frank Whitman, John Sims

“Stratigraphy, Morphology, and Paleoecology, Peccary Herd, Kentucky”

Geological Survey Professional Paper 790 1972

The Amazing Adaptable Whitetail Deer (Odocoileus virginiana)

March 5, 2013

The whitetail deer is probably the oldest large mammal species in North America.  Some whitetail deer fossils found in Florida  date to an astonishing 3.5 million years BP.  By contrast Homo sapiens as a species is roughly 200,000 years old.  Whitetail deer evolved from a similar species known as Odocoileus brachyodontus that existed from about 3.9-3.5 million years BP.  O. brachyodontus had different teeth and antlers from O. virginiana, but otherwise was a similar animal.  The direct ancestor of O. brachyodontus is unknown, but it was probably a species closely related to the Eurasian roe deer that crossed the Bering landbridge during the late Miocene.  As far as I know, a genome wide study of the deer family has yet to be completed.  The roe deer is the Eurasian species anatomically most similar to the Odocoileus genus, and therefore most likely to share a common ancestor.

Deer ecologically replaced the slender 3-toed species of horses and the American rhinos that formerly occupied the browsing niche in forested environments during the Miocene.  Ice Ages began occurring early in the Pliocene, and deer were better adapted to the resulting environmental changes than 3-toed horses and rhinos.  South of the ice sheets, a once year round climate of warm temperatures deteriorated to cycles of summer/hot and winter/cold patterns.  Drought became more frequent.  Broad-leafed trees evolved to drop their leaves during long cold winters and during prolonged droughts.  Deer were better able to survive in these deciduous forests.

Whitetail deer buck in its summer red coat.  This is the time 0f year pioneers collected deer hides and sold them for a dollar, hence the word “buck.”

Whitetail deer in its dull winter coat that helps it blend in a deciduous woods background.  Maybe it’s this adaptation that allowed it to survive when 3-toed horses couldn’t.

Whitetail deer thrive in fragmentary forests, explaining why they’ve been successful for so long.  Forests in southeastern North America have always been fragmentary.  Factors such as fire, windstorms, megafauna foraging, insect damage, plant diseases, and seed consumption create the patchy forest edge environments of constantly changing composition favored by whitetail deer.  The teeth of whitetail deer evolved from those of O. brachyodontus to enable them to include more grass in their diet–another advantage over Miocene browsers as the amount of grassland increased when climatic conditions changed.

Contrary to what I’ve read on some websites, during the Pleistocene, whitetail deer were just as widespread as they are today.  It is more accurate to say that in some regions they were less common than some now extinct species of megafauna.  In south Florida for example long-nosed peccaries apparently were more abundant than whitetails.  Llamas and tapirs likely competed with deer for the same resources in forested environments, while bison and horse were more successful in grasslands.  But deer were present just about everywhere, and I suspect they were the most common large mammal in the mid-south, even during most of the Pleistocene.

Modern anthropogenic land usage contributes to the fragmentary habitats whitetail deer are so well adapted to.  Men converted farmland to wooded suburbs, and abandoned farmland has become second growth forest.  Overhunting by man is the only threat to the existence of whitetail deer.  Whitetails do reproduce faster than all the extinct species of megafauna that couldn’t withstand human hunting pressure.  But in the past, intense human hunting has eradicated whitetail deer populations in many areas.  Deer were reported as scarce near large Indian settlements as early as 1704.  By the early 20th century deer were almost extinct in Georgia, but deer from the Great Lakes region were re-introduced here, and with proper management practices they remain abundant.  When I go jogging in my neighborhood I see fresh tracks daily, and I see  deer sprint in front of me about once every 6 weeks.  Some hunters complain deer are becoming less common, and they’re quick to blame coyotes.  I think the DNR needs to take a second look at the annual limit which is now up to 10.  30 years ago, the limit was just 3.  I find it ironic when hunters shoot 10 deer on their property, then wonder why they don’t see any deer the next year.  “It’s the coyotes,” they say.  Couldn’t it have something to do with the overgenerous season limits?

Whitetails are outcompeting mule deer (Odocoileus hemionus) in parts of the west undergoing suburbanization.  The latter prefer unbroken wilderness rather than the fragmentary habitat favored by their close relatives.  Mule deer evolved from an isolated population of whitetail deer some time during the early Pleistocene.  Some scientists proposed that the mule deer is a recent species resulting from a hybridization of blacktail and whitetail deer, but the fossil record and genetic studies debunk this hypothesis.  There are distinct fossils of mule deer dating to the mid-Pleistocene of California.  Moreover, studies of mule deer genetics show that blacktails and mule deer are the same species, despite sporting marked differences in physical appearance.  During the Last Glacial Maximum the Cordilleran Glacier separated mule deer from West Coast blacktails for thousands of years, accounting for the different physical traits, but they are still considered the same species by most experts.

Incidentally, Bjorn Kurten mentioned Pleistocene mule deer fossils found in Arkansas.  This is about 100 miles east of the species’ current range.  Whitetails are the only deer species found throughout the south, but the fossil record shows that elk (Cervus elephus), caribou (Rangifer tarandus), and the extinct stag-moose (Cervalces scotti) ranged into the mid-south during the Pleistocene.  Elk likely inhabited grassy hilltops in the piedmont region of Georgia until about 1760.  Elk fossils have been found as far south as Charleston, South Carolina.  Caribou fossils have been recorded from north Mississippi, north Alabama, north Georgia, the continental shelf off the coast of North Carolina; New Bern, North Carolina; and Charleston, South Carolina.  Most caribou fossils found in the south date to the Last Glacial Maximum, but 1 specimen came from interglacial strata. In the primeval wilderness of the Pleistocene there were probably a considerable number of stragglers that broke from huge herds located farther to the north, and these stragglers often wandered south.  There were no manmade barriers stopping them.  Fossils of the stag-moose have been found in Charleston, South Carolina and north Mississippi.  Elk, caribou, and stag-moose never could colonize the lower south and Florida because winters were too short and mild to limit the populations of blood-sucking insects that weaken northern species of deer.

Mule deer.  During the Pleistocene they ranged as far east as Arkansas.  Unlike whitetails, they prefer unbroken wilderness.

Elk.  William Bartram found elk bones on a grassy hilltop that I believe is located in Columbia County just above Augusta.  See https://markgelbart.wordpress.com/2013/01/01/a-serpentine-barren-in-georgia-burkes-mountain/

Woodland Caribou wandered south, especially during the Last Glacial Maximum when stragglers broke off from huge herds migrating south of the ice sheets in what is now southern Ohio, Kentucky, and Pennsylvannia.

Replica skeleton of a stag-moose, aka elk-moose.  Neither common name is accurate.  It wasn’t closely related to either elk or moose.  I prefer calling it the giant stag deer.  It was slightly bigger than a modern day moose.

South American red brocket deer.   All South American deer likely evolved from whitetails.  There’s no convincing evidence that any South American deer species ever lived in North America, though a member of the fossil forum claims he may write a paper about material he found in Florida that can be attributed to a South American species.

I used to think an additional extinct species of deer populated the upper south–the stilt-legged deer (Sangamona fugitiva).  But scientists analyzed the remains attributed to this species and determined all the material came from whitetails or elk.  Sangamona fugitiva is no longer considered a valid species, and as I related last week, fossil remains of marsh deer in Florida are probably from an incorrectly identified whitetail.

All South American deer probably evolved from whitetail deer.  Andean mountain deer, marsh deer, brocket deer, and pudus became geographically isolated from whitetails.  The latter do range into northern South America, but environmental change throughout the Pleistocene isolated the original populations of whitetails further south in the continent, resulting in varied speciation.  Dry climatic phases isolated tropical forests, causing them to become separated by vast grasslands and wetlands, and isolated populations of whitetails evolved into different species.