Archive for the ‘Pleistocene Mammals’ Category

Horse Toe Bones and 14,000 Year Old Human Shit

May 22, 2017

The oldest known evidence of human presence in North America is some pieces of shit excavated from Paisley Cave, Oregon.  Carbon-dating of this feces indicates humans crapped in the cave about 14,350 calendar years ago.  The contents of these turds consists of bison, dog, bird, fish, grass, and sunflower seeds.  One study found the amount of cholesterol and phosphate in the crap points to an animal with a vegetarian rather than an omnivorous diet, and the authors of this paper don’t believe it is human manure.  They suggest the human DNA extracted from the specimens are a result of contamination from people mishandling it.  However, the contents were mostly animal matter, so I don’t understand how the naysayers who authored this paper can come to this conclusion.  Other scientists note the presence of wolf or fox DNA in the crap.  The scientists who are convinced the turds are human believe a wolf or fox pissed on the human shit after people left the latrine.  The turds contain human hair–perhaps the best evidence people were the shitters here.  Dried crap stuck to their ass crack hairs and the hair came off when they wiped with leaves.

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Horse toe bones were found in Paisley Cave along with 14,000 year old human feces.

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A 14,000 year old human turd found in Paisley Cave, Oregon.

Many vertebrate bones and human artifacts have been discovered in the cave.  (See: https://markgelbart.wordpress.com/2010/10/29/the-paisley-cave-pre-clovis-site/ ).  Paleontologists studied the horse toe bones excavated near the human feces because they wanted to determine which species of horse co-existed with humans in this region then.  They believe with a >99% probability the toe bones belonged to an extinct species known as the Mexican horse (Equus conversidens). Most fossil material of this species has been found in Mexico, hence the name, but it likely occurred all across North America.  The Mexican horse was stocky and stilt-legged.

Paleontologists disagree over the number of horse species that lived in North America during the late Pleistocene.  Some believe there were 2 species, while others think there were more than 14 species.  Genetic evidence supports the proposed smaller number of species.

I have no doubt humans were responsible for the extinction of North American horses through overhunting and disruption of ecosystems.  When Europeans re-introduced horses to North America during the 16th century, horses went wild and thrived everywhere on the continent.  It seems unlikely an environmental change capable of causing horse extinctions occurred for such a short interval some time between 10,000 BP and 1500 AD.  Horses eat grass and coarse vegetation–plant material that never became scarce during any climate phase or change.  Climate change models of extinction don’t work at all for such an adaptable and widespread animal as the horse.

I remember when I first started studying the debate over megafauna extinction.  Opposition to human overkill as a cause of extinction centered around the flimsy argument that there was a lack of archaeological evidence of humans hunting horses in North America.  Since then, irrefutable proof humans hunted horses here has been unearthed at several sites.  Wally’s Beach in Alberta, Canada was the first site where archaeologists agreed evidence humans hunted horses was unmistakable. Bluefish Cave in the Yukon is located north of the former Cordilleran Ice Sheet.  Evidence humans hunted and ate Ice Age horses has also been discovered in this cave, and it dates to as early as 24,000 years ago.  Humans carried horse, caribou, elk, dall sheep, bison, and bird into the cave.  36,000 mammal bones have been excavated from this site.  Wolves, lions, and foxes, in addition to people are responsible for the bone accumulation.  And now, South American archaeologists believe a cave in Argentina holds evidence of human exploitation of horse.  Stone tools are found in association with human-modified bones of horse, hippidion (an exclusively South American species of horse), llama, toxodon, giant armadillo (Eutatus) and ground sloth (Megatherium and Glossotherium).

The evidence humans did hunt megafauna is mounting but will probably never convince old school archaeologists who (I believe) stubbornly refuse to admit they were wrong for so many years.

References:

Bourgeon, L.; A. Burta, T. Higgins

“Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radio-carbon dates from Bluefish Cave, Yukon”

Plos One January 2017

McHorse, Brianna; Edward Davis, Eric Scott, Dennis Jenkins

“What Species of Horse was Coeval with North America’s Earliest Humans in the Paisley Caves?”

Journal of Vertebrate Paleontology September 2016

Politis, Gustavo; M. Gutierrez, D. Rafus

“The Arrival of Homo Sapiens into the Southern Cone at 14,000 Years Ago”

Plos One September 2016

Sistiaga, A.; F. Berna, R. Laursen, P. Goldberg

“Steroidal Biomarker Analysis of a 14,000 Year Old Putative Human Coprolite from Paisley Cave”

Journal of Archaeological Science 2014

 

First Bone-eating Dog (Borophagus sp.) Tooth Found in South Carolina

May 17, 2017

The Borophagine dogs were an incredibly successful lineage of carnivores that lived from ~34 million years BP to ~2 million years BP and perhaps beyond.  They ranged throughout North America from coast to coast and from Canada to Honduras.  16 species of Borophagine dogs are known from 12 different fossil sites in Florida alone, and in the rest of the southeast specimens have also been found in North Carolina and Maryland.  Recently, an amateur fossil collector found 1 pre-molar of a Borophagus in a spoil pile at the Martin-Marietta Orangeburg Quarry located in Orangeburg County, South Carolina.  This animal was probably common in South Carolina for millions of years, but this is the only known evidence it ever existed in the state.  Paleontologists examined the tooth and determined it compared favorably to a pre-molar of Borophagus hilli, a species that reached a weight of 130 pounds.  The age of this fossil is estimated to be between 3.9 million years BP-3.1 million years BP based on associated microfossils.  B. hilli co-occurred with another species of Borophagine dog–B. diversidensThey must have occupied different ecological niches, maybe like modern day wolves and coyotes.

Jaw bone of Borophagus hilli–the Pliocene bone-eating dog.

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Artist’s depiction of the extinct bone-eating dog.  They had bulging foreheads.  Their teeth and jaws were similar to those of the extant spotted hyena–an example of convergent evolution.

Early species of Borophagine dogs were omnivorous.  Epicyon haydenii was the largest known species of canid in history, reaching weights of over 500 pounds.  This species lived between 12 million years BP-6 million years BP, and it probably occupied a bear-like ecological niche.  Borophagine dogs later evolved into more carnivorous forms, resembling modern day spotted hyenas (Crocuta crocuta) in build and dentition, hence the reason they’re often called bone-eating dogs.

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Epicyon haydenii was the largest known canid in history, growing as large as a grizzly bear.  They were more omnivorous than their later descendants.  They lived during the Miocene.

Borophagus sp.

Scan of the lower 4th pre-molar of a Borophagus.  This is the only fossil evidence found in South Carolina of a species that was formerly common in the region for millions of years.

Despite their long reign as an important carnivore in the American ecosystem, Borophagine dogs became extinct during the late Pliocene or early Pleistocene.  The last species of Borophagine dogs co-existed with dogs belonging to the Canidae family for millions of years.  The Canidae were newcomers from Eurasia that crossed the Bering land bridge to reach North America.  Species from the Canidae family were better able to adapt to changes in the environment during the early Pleistocene and likely outcompeted Borophagine dogs, contributing to their extinction and completely replacing them ecologically.

Reference:

Tseng, Z. Jack; and Jonathan Geisler

“The First Fossil Record of Borophagine Dogs (Mammalia: Carnivora) from South Carolina USA”

Journal of Vertebrate Paleontology 36 (2) March 2016

Dumpster Dingoes

May 9, 2017

Bacteria. Cockroaches. Flies. And even higher organisms. Mice. Rats. Sea gulls. Crows. Bald Eagles. Cats. Dogs. Wolves. Bears.  These are just some of the organisms that benefit from the food waste produced by humans.  We waste up to 40% of the food we produce.  The proliferation of Homo sapiens since the late Pleistocene has been detrimental to many species, but others have adapted to our presence.  Scientists estimate anthropogenic sources, including livestock and garbage, make up 32% of the worldwide gray wolf diet.  The last surviving population of Asiatic lions almost entirely subsists on livestock.  Studies show Australian dingoes and red foxes that live near landfills have smaller home ranges and higher survival rates than other individuals of the same species.  Dingoes living near garbage dumps grow fat and mate with domestic dogs, producing hybrids that could be called dumpster dingoes.  This same study found black bears foraging around dumpsters have shorter lifespans because they come into conflict with people and get shot.

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Landfills are excellent sites for bird watching.  They attract gulls, crows, and vultures.  I have even seen a bald eagle soaring over one.

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Dogs evolved from wolves that hung around human refuse heaps.

Dingoes are super efficient hunters that prey on almost everything they can kill

Dingo chasing a kangaroo.  Dingoes that hang around landfills get fat and lazy and mate with domestic dogs.

The existence of human refuse heaps likely spurred the evolution of wolf into dog.  The physical characteristics that differentiate dogs from wolves share the same genetic pathway with tameness.  The 2nd and 3rd generations of canids with the least flight response develop the floppy ears and multi-colored coats common in domestic dogs.  Some scientists think it possible some modern day wolves scavenging dumpsters could again evolve into a type of dog.

Genetic studies suggest dogs developed the ability to digest more starch about 4000-7000 years ago–another step in the ongoing evolution of wolf to dog.  This coincides with the development of agriculture when humans began cultivating cereal grains.  Dogs with digestive systems capable of producing more amylase, the enzyme that helps convert starch to sugar, were better able to survive on bread when humans started consuming more cereal grains instead of (or as a supplement to)  meat.

Dingoes descend from dogs brought to Australia about 4000 years ago by people from the subcontinent of India who later assimilated with Australian aborigines.  Dingoes are primitive dogs similar enough to their wolf ancestors that they can revert to the wild and thrive.  Dingoes rapidly became the top non-human predator in Australia.  Most people are unaware dingoes live in America as well. ( See: https://markgelbart.wordpress.com/2013/02/11/the-american-dingo/ ) Native Americans brought primitive dogs with them from Asia, and some of them went wild here just like they did in Australia.  North American dingoes are known as Carolina dogs and were not recognized as a distinct wild canid until a scientist found them running wild during the 1970s on the Savannah River Site in South Carolina.

The observed differences between wolf, dingo, and dog are a good example of recent evolution.  They also show the line between species can be blurry.  All 3 can interbreed and produce fertile offspring.  So some scientists think dogs and dingoes should be classified as subspecies of wolf.  On the other hand the physical and behavioral characteristics of each are quite different, and some scientists still classify them as distinct species.  Domestic dogs are entirely dependent upon humans, dingoes (a transitional form between dog and wolf) can take us or leave us, and wolves avoid us and probably wish humans would become extinct.  I prefer classifying them as separate species based on behavioral differences.

References:

Marshall-Pescini, Sarah; Ingo Besserdick, C. Kratz, F. Rang

“Exploring Differences in Dogs and Wolves’ Preference for Risk in Foraging Trash”

Frontiers in Psychology August 2016

Newsome, Thomas; Gary Ballard, Matthew Crouther, and Chris Dickman

“Dietary Niche Overlap of Free-Roaming Dingoes and Domestic Dogs: The Role of Human-Provided Food”

Journal of Mammalogy April 2014

Oro, Daniel; et. al.

“Ecological and Evolutionary Implications of Food Subsidies from Humans”

Ecology Letters October 2013

 

 

The Pleistocene Great Smoky Mountains

April 23, 2017

I renewed my subscription to the Southeastern Naturalist, so I could read a recent monograph that inventoried the mammal fauna of the Great Smoky Mountains National Park.  According to this paper, 68 species of mammals have been documented in the park, and 1 scientist predicts an additional 4 species might eventually be found there.  I suspect this number is greatly exaggerated–many of the species are small animals not documented in the park since the initial survey when the park was established in the 1930’s.  Those species not documented recently could very well be extirpated from the park.  The flora of the Great Smoky Mountains National Park is impressive but don’t plan a trip and expect to see much wildlife.  I visited the park once and saw just 1 squirrel and no other mammals besides lots of people.  There are 24 species of insectivores and bats allegedly inhabiting the park.  These species are difficult to see and enjoy.  That leaves 44 species and of these only 5 are considered megafauna (animals weighing over 40 pounds). The “big 5” are white tailed deer, elk, black bear, wild boar, and coyote.  The latter 2 are considered invasive, but I think of the coyote as a native species that is recolonizing former territory occupied during the Pleistocene.

There are probably more white tailed deer outside the park in the surrounding farmland.  White tailed deer prefer forest edge habitat, and most of the park has succeeded to old growth.  Elk were re-introduced here in 2001, but they inhabit a small area of the park difficult to access.  The road leading to this spot is a dangerous single lane dirt path on the side of a mountain.  Supposedly, the black bear population in the park is about 1600.  During the summer black cherries (Prunus serotina) make up 25% of the bear’s diet.  Garbage provides 8% of their diet here.  The author of the below referenced monograph claims to have several photographs of cougars taken by park visitors circa 2003.  These may be of captive cougars released by owners who no longer wanted to care for them.  Cougars are normally secretive, and semi-tame cats may have been easier to photograph.  I doubt there is a breeding population of cougars in the park, but I wouldn’t rule it out, and they may eventually recolonize the region, if they keep expanding their range from the west and south Florida.

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Location of the Great Smoky Mountains Park.  The diversity of megafauna species in this park is much lower now than it was in this region during the Pleistocene.

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Strange as it may seem, wild black cherries make up to 25% of the black bear’s diet during mid to late summer in the Great Smoky Mountains National Park.

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The below referenced monograph reports a population of 30 striped skunks inhabit the Cades Cove Campground of the Great Smoky Mountains National Park.  They den in drainage culverts.  Avoid them or you will endure a stinky vacation.

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A fluctuating population of endangered Indiana bats roosts in a cave in Cades Cove.  Bats can be seen at dusk.

The variety and abundance of megafauna in the Great Smoky Mountains National Park is disappointing, but it was spectacular during the Pleistocene.  The natural communities then were similar to those of today, but during cold glacials there probably were more spruce trees and grassy balds and in higher elevations there may have even been tundra-like environments.  Here’s a list of large mammals (based on fossil evidence) that definitely inhabited the park region until ~11,000 BP or beyond.

Jefferson’s ground sloth

Harlan’s ground sloth

tapir

horse

half-ass

mastodon

long-nosed peccary

flat-headed peccary

stout-legged llama

helmeted musk-ox

bison

white-tailed deer

caribou

elk (probably not until 15,000 years BP)

giant beaver

black bear

Florida spectacled bear

giant short-faced bear

cougar

jaguar

saber-toothed cat

scimitar-toothed cat

coyote

dire wolf

Here’s a list of additional megafauna species that likely inhabited the park but whose nearest fossil remains are a considerable distance away.

pampathere

stag-moose

Columbian mammoth

woolly mammoth

Columbian mammoth x woolly mammoth hybrids

gompothere (during warm climate cycles)

giant lion

dhole

The Pleistocene Great Smoky Mountains hosted ~31 megafauna species compared to the present day total of 5.  This is a >80% reduction.  How sad.

Reference:

Linzey, Donald

“Mammals of the Great Smoky Mountains National Park: 2016 Revision”

Southeastern Naturalist 15 Monograph (8) 2016

 

Hares (Lepus sp.) in Southeastern North America during the Late Pleistocene?

April 17, 2017

Librarians can be a pain in the ass.  On 1 occasion I attempted to check out a book from the Augusta College library.  The librarian told me I needed to purchase an alumni card for the privilege of borrowing a book from my alma mater.  I shelled out $25 for the card, and the same #!#!en librarian still wouldn’t let me take the book home.  Another time I was seeking an old Alabama Journal of Science article.  The authors of the article were dead or in a nursing home so I couldn’t get a copy from them.  The journal posts new issues online but not ones this old.  I contacted a librarian from the Alabama library system and asked her to loan the journal to my nearest library where I could pick it up or at least send me a Xeroxed copy of the article.  I offered to pay for postage and use of the copy machine.  She refused because I was not affiliated with the University of Alabama library system.  My efforts to obtain this article have been stymied for 8 years, but I recently learned a surprising tidbit of information from this article that was referenced in another paper I recently came across.  A tooth identified as comparing favorably to hare was found at Bogue Chitto Creek in Dallas County, Alabama; a site where subfossil remains of late Pleistocene species are occasionally discovered.  Bones of hares have been excavated from 7 sites in Florida that date from the Miocene to the early and mid-Pleistocene, but hares are otherwise unknown from late Pleistocene sites this far south, making this an unique find.

Scientists can’t identify this specimen to a species level based on just this single tooth. Bjorn Kurten, co-author of Pleistocene Mammals of North America, states it is difficult to distinguish between rabbit (Sylvilagus sp.) and hare (Lepus sp.)  teeth, and discerning the difference between hare species based on teeth is even harder, if not impossible.  The tooth may have been from a white-tailed (Lepus townsendii), black-tailed (L. californicus), antelope (L. alleni), or an unknown extinct species of jackrabbit that occupied a small geographic range during the late Pleistocene.  This site is probably too far south for another species of hare–the snowshoe (L. americanus).  It’s also possible the tooth is incorrectly identified and belonged to a true rabbit.  Cottontails have long been abundant all over the south, and they are well represented in the fossil record here.  When paleontologists designate a specimen as comparing favorably (cf), they are not 100% certain of the identification.

Map of Alabama highlighting Dallas County

Bogue Chitto Creek, flows through Dallas County, Alabama.  Many Pleistocene fossil specimens have been found in this creek, including the tooth discussed in this article.

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Present day range map of the  black-tailed jackrabbit.  Western species of hares lived in the southeast during the early to mid-Pleistocene.  Scant evidence suggests they may have occurred in the Black Prairie region of central Alabama during the late Pleistocene as well.

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Black-tailed jackrabbit.  Hares differ from true rabbits.  Their young are born with their eyes open and able to hop about and flee from predators.

Bogue Chitto Creek flows through the Black Prairie region of central Alabama.  The compact clay soils here favor grass over trees, and the Black Prairie region itself extends into neighboring Mississippi and Georgia.  Western hare species prefer large treeless plains, and the predominance of this environment here may explain why a relic population of hares existed in this region during the late Pleistocene.  Other environments in the southeast often climax into forests where western hare species can’t survive.  Lagomorphs (hares, rabbits, and pikas) are susceptible to disease outbreaks, and relic populations of hares in the southeast could have easily succumbed to pestilence.  Before I learned about this tooth, I wondered why there was no evidence of hares in the southeast during the late Pleistocene when arid climates led to a greater prevalence of open environments.  This evidence suggests they may have had a local distribution in some parts of the south then.

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Snowshoe hares turn white in winter and brown in summer.

Unlike their western relatives, snowshoe hares prefer forested environments.  A leg bone of a snowshoe hare was found in Cave ACb-2 in Colbert County, Alabama.  This is the southernmost known occurrence of this species, although this is not far from its present day range.  There is anecdotal evidence snowshoe hares occurred as far south as the Great Smoky Mountains National Park as recently as the early 20th century where they possibly still exist today.  Snowshoe hare remains dating to the late Pleistocene have also been found in 2 other southern states–Arkansas and Kentucky.  They require areas with snowpack on the ground for at least part of the year.

Reference:

Ebersole, Jon; and Sandy Ebersole

“Late Pleistocene Mammals of Alabama: A Comprehensive Faunal Review with 21 Previously Unreported Taxon”

Alabama Museum of Natural History Bulletin 28 December 2011

 

Pine Martens (Martes americana) Lived in Southeastern North America during the Late Pleistocene

April 13, 2017

If humans didn’t colonize North America, I believe the pine marten would have a much wider range than it does today.  Presently,  this small carnivore is confined to boreal and mixed forests in Canada, the northern Rocky Mountains, and upper Maine.  In historical times they also ranged into New England.  During the late Pleistocene pine martens lived at least as far south as northern Alabama, and they probably ranged into the piedmont.  (The fossil record of the southeastern North American piedmont region is poor.  I rely on educated speculation to imagine the faunal composition there.)  Pine marten remains dating to the late Pleistocene have been excavated from Cave ACb-2 in Colbert County, Alabama, as well as 2 sites in Tennessee and 2 in Virginia–far south of their present day range.  Pine martens live in low densities, hunting small mammals and birds on the forest floor and in tree tops.  Unlike their relative, the fisher (M. pennanti), pine martens don’t readily re-establish populations after they’ve been extirpated from a certain area.  Archaeological evidence suggests fishers ranged as far south as north Georgia until European colonization when their range was greatly reduced by increased fur trapping, and they thrive wherever they are re-introduced.  But pine martens struggle to increase their populations when they are re-introduced.

Native Americans killed pine martens using deadfall traps.  A heavy rock was propped up by a stick attached to a piece of meat with a string.  The rock crushed the pine marten pulling at the bait.  Pine martens often fail to replenish their populations after humans begin trapping them in a certain area.  They’ve been able to survive in Canada because this region is more sparsely inhabited by people.  The denser population of humans in the southeast not only trapped out the pine martens but planted agricultural fields and cleared the deep forest habitat they require.  Humans can be just as detrimental to some species of small animals as they are to megafauna populations.

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Pine marten. They are about the size of a small house cat.

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Present day range map of the pine marten.  Most of this range was under glacial ice during the Ice Age.  However, they lived south of the ice sheet at least as far south as Alabama.

Map of Alabama highlighting Colbert County

Fossil evidence of pine marten was found in Cave Acb2 in Colbert County, Alabama.  This is its southernmost known occurrence.

Some scientists speculate evidence of pine martens in north Alabama during the Ice Age suggests the region was covered with boreal spruce forests because this is the type of environment where pine martens occur today.  As I’ve noted in previous blog entries, the Ice Age forest that existed in the upper south then was likely a mixed forest consisting of an extinct temperate species of spruce (Critchfield’s) and hardwoods such as oak, hickory, walnut, elm, etc.  Temperatures were only slightly cooler in this region then than they are today.  I believe humans, not climate change, are the reason for the pine marten’s range reduction.

Reference:

Ebersole, Jon; and Sandy Ebersole

“Late Pleistocene Mammals of Alabama: A Comprehensive Faunal Review with 21 Previously Unreported Species”

Alabama Museum of Natural History Bulletin 28 December 2011

Coyote (Canis latrans) Evolution

March 2, 2017

The coyote is a remarkably adaptable and intelligent animal. The evolutionary history of this species began about 43 million years ago when its ancestors, the caniforms (dogs, bears, weasels, skunks, and raccoons) diverged from the feliforms (cats, hyenas, mongoose, and civets).  The canis genus likely originated in North America over 5 million years ago, having evolved from a primitive wolf-like animal known as eucyon.  Johnston’s coyote (Canis lepophagus) was an early member of the canis genus that lived in North America during the Pliocene from ~5 million years BP-~2 million years BP.  Most paleontologists who study the anatomy of canids believe C. lepophagus was ancestral  to wolves, coyotes, and dogs. Wolves crossed the Bering land bridge and colonized Eurasia, while coyotes stayed in North America.

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Canis lepophagus attempting to scavenge a carcass of a llama defended by a Borophagus, the bone-eating dog.  This illustration depicts a scene that may have occurred during the early Pliocene or late Miocene over 3 million years ago.  Canis lepophagus is thought to be the common ancestor of wolf, dog, and coyote.

At the Rancho La Brea Tar Pits in California coyote bones are the 3rd most common specimens to be excavated here behind dire wolves (Canis dirus) and saber-toothed cats (Smilodon fatalis).  Timber wolf (Canis lupus) skeletal material is present but uncommon.  The abundance of carnivore specimens from this site allows scientists to study changes over time in the anatomy of these species.  Ice Age coyotes from this locality were larger and more powerful than present day coyotes, and they had larger jaws and teeth.  There are probably a couple of reasons for this size disparity.  Pleistocene coyotes hunted larger prey and had a better diet.  They may have hunted juvenile individuals of megafauna species such as horse, bison, camel, and llama; and there was more meat to scavenge.  Moreover, they had to compete with larger carnivores and likely lived in bigger packs.  Dire wolves competitively excluded timber wolves from coyote range.  This benefitted coyotes as well because there was less of an ecological niche overlap between dire wolves and coyotes than there is between timber wolves and coyotes.  Less than 1000 years after the extinction of the Pleistocene megafauna, coyotes evolved to their present day size and stature.

Dire wolves are long gone and timber wolves have been extirpated from most of their former range, but coyote populations are increasing, and they have re-colonized eastern North America within the past century.  Coyotes are 1 of the few carnivores smart enough to avoid poison bait and traps.  Studies show they produce larger litter sizes in response to human hunting pressure.  Though human hunting of coyotes may cause a temporary decrease in their populations, in the long term their populations increase because they begin producing larger litters.  This explains why their populations increase despite being considered a pest that can be hunted year round with no bag limit.

Coyotes in northeastern North America interbred with the last timber wolves in eastern Canada and dogs, and these coyote-wolf-dog hybrids live in large cities and suburbs.  Genetic studies suggest these hybrids are 65% coyote, 25% wolf, and 10% dog.  Characteristics inherited from dogs help them tolerate urban noise, and some have even learned to look both ways before they cross roads.   They’ve adapted well to living on golf courses, city parks, abandoned farmland, vacant lots, cemeteries, and roadside ditches where they have frequent access to roadkill.  I think coyote-wolf-dog hybrids have colonized southeastern North America as well.  I’ve seen some that look like western coyotes, and others that resemble wolves.  More genetic studies of southeastern coyotes may confirm my hypothesis.

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Coyote-wolf hybrids have colonized northeastern North America.  I hypothesize some coyotes in southeastern North America have also bred with wolves and dogs.

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These photos help distinguish between coyote-wolf hybrids and pure bred coyotes.  I’ve seen canids in Georgia that resemble both.

Reference:

Meachen, Julie; and Joshua Samuels

“Evolution in Coyote (Canis latrans) in Response to Megafaunal Extinctions”

PNAS 2012

The Unknown Mating Habits of Saber-toothed Cats (Smilodon fatalis)

February 5, 2017

The average male saber-toothed cat was only slightly larger in overall body size than a female saber-tooth, but they had significantly larger mandibles and upper canines (the fangs).  This is in contrast to most species of cats today.  Most male cats and especially lions are much larger than the average female of their species.  The mating habits of Smilodon are completely unknown, and we can only speculate about them based on the knowledge that they differed in size above the neck, but not much elsewhere aside from the sexual organs.

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Smilodon had low sexual dimorphism in body size, but males had significantly larger mandibles and upper canines.  Did males share their larger kills with females as way to attract them?

I believe saber-tooth mating habits may have been notably different from those of all extant species of cats.  The saber-toothed and the scimitar-toothed cats ( Dinobastis or Homotherium ) belonged to an extinct subfamily of cats known as the Machairodontinae.  The Machariodontinae diverged from all other cats an estimated 13 million years ago, very early in cat evolution, and they have no close living relatives today.  They were more closely related to other carnivores than modern day species of cats are.  Perhaps they lived in matriarchal societies like the spotted hyena ( Crocuta crocuta ), another species that shows low sexual dimorphism (the females are actually slightly larger than the males).  Or maybe, as in the wolf ( Canis lupus only the dominant male and female of the pack were allowed to mate.  However, scientists disagree over whether saber-toothed cats were social or solitary animals.

Some scientists argue evidence from the La Brea Tar Pits of severely injured saber-tooths that survived traumatic debilitating injuries suggests they must have lived in groups.  But others believe that even a severely injured saber-tooth could have lived for a long time by scavenging.  A saber-tooth in a bad mood due to pain could have easily intimidated smaller predators from their kills. Moreover, their small braincases also indicates they didn’t live in groups.  I suspect they were solitary cats, though mothers probably hunted cooperatively with nearly grown cubs when she was training them how to hunt.

The males were able to bring down larger prey than the females because their bites, aided by the larger jaws and fangs, were deadlier.  Perhaps this was an element of their mating system.  Females that came to scavenge the male-killed prey were tolerated by the males, and the heavy meal caused them to go into instant heat.  Maybe females followed the most successful hunting males with the frequent nutritious meals triggering more frequent ovulation.

I’ve always been fascinated over how recently this strange exotic animal became extinct–only ~10,000 years ago.    It’s frustrating not to be able to know more about how it lived.  Relying on guesswork is just not as satisfying as knowing.

References:

Christiansen, P.; and John Harris

“Variation in Craniomandibular Morphology and Sexual Dimorphism in Pantherines and the Sabercat Smilodon fatalis

Plos One Oct 2012

Meachen-Samuels; J.A.; W.J. Binder

“Sexual Dimorphism and Ontogenetic Growth in the American Lion and Sabertoothed Cat from Rancho La Brea”

Journal of Zoology 2010

Mammoths and Mastodons were Year Round Residents of the Ohio River Valley during the Late Pleistocene

January 27, 2017

The bones and teeth of an extinct animal provide scientists with information about the life history of that particular individual.  Recently, 2 scientists analyzed the chemistry of 8 mammoth ( Mammuthus columbi ) and 4 mastodon ( Mammut americana ) teeth collected from Hamilton County, Ohio and Bullitt and Gallatin Counties, Kentucky–in other words, the Cincinnati area.  They determined 11 of these animals spent their entire lives in what was to become the Cincinnati area.  They also learned 7 of the mammoths ate different plant foods than the mastodons, but the diet from 1 individual mammoth did overlap with mastodon diets.

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Hamilton County, Ohio

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Mammoths and Mastodons lived year round in the Ohio River Valley.  They were 2 completely different species of proboscidean.

Scientists are able to determine where an animal lived during its lifetime by measuring the ratio of strontium and strontium isotopes in their teeth.  Strontium leaches from local bedrock into the water supply, and animals absorb the strontium into their bones when they drink.  Different geographical regions exhibit different ratios of strontium isotopes, so it’s possible to figure out where an animal spent time during its life.  A previous study of mastodon and mammoth teeth collected from Florida determined mastodons there migrated back and forth from central Florida to central Georgia, while Florida mammoths did not migrate.  But this study suggests most of the mastodons that lived in the Ohio River valley did not migrate.  However, there were exceptions.  The strontium ratio from 1 specimen indicated this individual wandered north from either north Georgia or southern Tennessee to the Ohio River valley.  The authors of this study estimated this could have been accomplished in as little as 5 days based on how fast modern elephants can travel.

The bone chemistry tells us mammoths mostly ate grass, while mastodons ate plants that grew in forested environments.  But again there was 1 exception–1 mammoth that fed upon forest vegetation.  During the Last Glacial Maximum much of this region was a cool arid steppe environment.  After the nearby ice sheet retreated, the steppe was transformed into an open spruce parkland, then eventually an oak and hardwood dominated forest.  This mammoth apparently adapted to the latter changes.

Mammoths and mastodons had no need to migrate away from the Ohio River.  The rich floodplain habitat and numerous mineral licks provided enough nutrition to support year round populations of both.

Reference:

Baumann, Eric; and Brook Crowley

“Stable Isotopes Reveal Ecological Differences among now Extinct Proboscideans from the Cincinnati Region, USA”

Boreas 2015

Donald Grayson’s Disingenous Case Against Overkill

January 23, 2017

I almost chose not to read Donald Grayson’s most recent book, Giant Sloths and Sabertooth Cats: Extinct Mammals and the Archaeology of the Ice Age Great Basin.  Grayson is a long time skeptic of the hypothesis that man overhunted Pleistocene megafauna to extinction, and he has authored and co-authored a number of papers explaining his position.  In my opinion overhunting by man is the only explanation for the extinction of Pleistocene megafauna that makes sense.  I’ve read his papers and consider his arguments highly illogical and unfair.  But I did purchase his book because I try to absorb all the knowledge I can about my favorite subject–the late Pleistocene ecology of North America.  I don’t have to agree with an author about everything to enjoy their work.  I saw his chapter on extinction was short, just a small portion of the book, and I assumed he would simply rehash his tired old case against overkill.  However, I was shocked at the way he misrepresented the results of a paleoecological study.  He implies the results of this study support climate change models of Pleistocene megafauna extinctions.  In fact this paper specifically states the opposite.

Image result for Giant sloths and sabertooth cats extinct mammals and the archaeology of the Ice Age Great Basin

Donald Grayson’s newest book.  His chapter on extinction is marred by gross deception.

Don Grayson, photo by Mary Levin, UW Photography, 2011

Donald Grayson is an archaeology professor at the University of Washington.  

On page 287 of the above book, Grayson wrote “…paleoecologist Jacquelyn Gill and her colleagues took a close look at tiny bits of Ice Age history extracted from 3 lakes and marshes in New York and Indiana.”    Grayson fails to mention the data from the lakes in New York was gathered in a study led by Guy Robinson (1).  (I will number the studies mentioned in this blog post and list them below.)  Guy Robinson’s team took samples of sediment from some New York lakes and marshes, radiocarbon dated different chronological layers of it, and measured and analyzed the volume of pollen, charcoal, and dung fungus spores in each layer.  The volume of dung fungus spores is used as a proxy to estimate populations of megafauna.  They determined local extinctions of megafauna were staggered throughout 2 thousand years, and they concluded this ruled out climate change as a cause of the megafauna extinctions.  If climate change caused the extinctions, they believed the extinctions at these different sites would be simultaneous.  Instead the local extinctions occurred at different times at different sites, and it appears as if nomadic humans were overhunting megafauna at 1 site, then moving on to another, though these local extinctions occurred shortly before the Clovis cultural era.  Increases in charcoal while megafauna populations were declining is additional evidence of probable human impact.  Jacquelyn Gill, the lead author of the paper (2) Grayson referred to in his book,  details a similar study of an Indiana lake.  The authors of this study also found that megafauna populations declined before the Clovis cultural era but also before climate caused changes in the local plant composition.  They believe human impacts are still a “plausible” cause of megafauna extinction, and they wrote “our data thus rule out the hypothesis that (i) climate-forced changes in vegetation drove the megafaunal decline, and (ii) no-analogue plant communities were created by megaherbivory.”  Megafauna became locally extinct here before the pollen evidence suggests changes in the plant community occurred.  They believe humans can still be implicated in megafauna extinctions at this site because increases in charcoal indicated humans were setting fire to the landscape during the period of megafauna decline, and there is evidence of human butchery of mammoths in southeastern Wisconsin during this same time period, suggesting that humans were likely hunting them at this location as well.

It is very dishonest of Grayson to imply these studies support climate-change models of extinction when the authors of these studies specifically state the opposite.  He should have at least informed his readers of their conclusions and explain why he has a different interpretation of the data.  The authors of these studies do note that megafauna decline occurred during a warm phase of climate, but they believe, if climate played a role, it had to be some other mechanism besides climate-driven changes in the environment.  The accepted logic behind climate change models of extinction is that changes in climate decreased the plant foods necessary to maintain viable populations of megaherbivores.  These studies show this is not the case.  Moreover, fossil coprolites show the plants Ice Age megafauna ate are still common on the landscape today, and isotopic studies indicate they were not picky feeders, but instead ate a wide variety of foods.  I think the warm climate phase provided a greater variety of edible plant foods for humans, thus increasing human populations which in turn was detrimental to megafauna.

There are many regions in North and South America where the environment did not change substantially during the most recent glacial-interglacial transition including the pampas of Argentina, southern California, and southeastern North America, especially Florida and the coastal plain.  Climate change models of extinction just don’t make sense in these regions.  Most species of megafauna enjoyed continent wide distributions, and they endured 30 glacial-interglacial transitions over the past 2 million years without suffering extinctions, yet they did become extinct about the same time man appears in the archaeological record.  This can’t be coincidence.

Grayson focuses his arguments against overkill on the Clovis blitzkrieg model of extinction.  This model proposes humans rapidly overhunted megafauna to extinction within the 500 year period of the Clovis cultural era.  There is another model of overkill: humans were responsible for overhunting megafauna, but it took place over several thousand years and also involved a change in fire regime and other human impacts.  This is known as the protracted overkill model and it is the one I favor.  Grayson ignores this model.  He doesn’t acknowledge the likelihood that pre-Clovis humans impacted megafauna populations.  I’m sure he would point out the lack of archaeological evidence for this.  His main objection to the blitzkrieg model is also a lack of archaeological evidence…he believes there are not enough kill sites (direct evidence that humans killed a beast) to justify the overkill hypothesis.  This objection is unreasonable.  99.999…etc% of the individuals of a species that ever lived left no fossil evidence at all.  It is ridiculous to expect to find fossil evidence of the last individuals of a species that just happened to be killed by men.  Moreover, Grayson never quantifies how many kill sites archaeologists would need to find before he would be convinced humans were responsible for the demise of the megafauna.  He needs to put an exact number on it or cease his objections.  Despite the odds against it, there are numerous kill sites and evidence of human-butchered megafauna bones.  Grayson dismisses over half of them, sometimes unfairly, though sometimes his skepticism is warranted.

Grayson falsely claims the overkill hypothesis has “little going for it” and he sounds annoyed on pages 279 and 280 of his book when he laments its acceptance in the popular media.  He might be annoyed because in recent years the  overwhelming number of paleoecological and statistical studies suggest man at least played some role in megafauna extinctions.  Grayson glosses over a statistical study led by G.W. Prescott (3) that determined both man and climate played a role in the end Pleistocene extinctions.  But 2 recent studies of worldwide extinction chronology (4) (5) determined extinctions are more closely tied to human expansion than climate change.  In the study led by C. Sandom they note extinctions have been severe in climatically stable regions.  They write: “Human arrival was a necessary factor for extinctions, whereas climate variation was a contributory one, enhancing regionally the effects of anthropogenic impacts on additive rather than synergistic ways.”

References:

(1) Robinson, G.S. ; L.P Burney and D.A. Burney

“Landscape Paleoecology and Megafaunal Extinction in Southeastern New York”

Ecological Monographs 2005

(2) Gill, J.L.; J.W. Williams, S.T. Jackson, K.B. Lininger, and G.S. Robinson

“Pleistocene Megafauna Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America

Science 2009

(3) Prescott, G.W. et. al.

“Quantitative Global Analysis of the Role of Climate and People in Explaining Late Quaternary Extinctions”

PNAS 2012

(4) Aravjo, Bernardo et. al.

“Bigger Kill than Chill: the Uneven Roles of Humans and Climate on Late Quaternary Megafaunal Extinctions”

Quaternary International 2015

(5) Sandom, C. et. al.

“Global Late Quaternary Megafauna Extinctions Linked to Humans, not Climate Change”

Proceedings of the Royal Society 2014

http://rspb.royalsocietypublishing.org/content/281/1787/20133254