Archive for January, 2012

The Eerie Call of the Common Loon (Gavia immer immer)

January 29, 2012

The call of the loon sounds ghostly.  I imagine the howling of dire wolves and the eerie calling of loons made living in the Pleistocene kind of spooky.  Loons are in the order Gaviformes which is always the first order listed in books about North American birds, meaning they are considered the most primitive avian group living on the continent. Of all the North American birds they must be the closest living relatives of the dinosaurs.  Perhaps some species of dinosaurs had a smilar vocalization.  Below is a link to a youtube video from the Cornell University ornithology department that includes eerie cries of loons.

http://www.youtube.com/watch?v=4ENNzjy8QjU

Common loon.

Loons dive under water and catch small fish–their primary prey, though they also feed upon aquatic invertebrates, insects, and some water plants.  They can take large fish as well, but need to drag them to shore and mangle them before dining.  Loons like to nest on uninhabited islands in lakes, explaining why they migrate north during spring to places like Minnesota where there are lots of lakes.  I always thought of loons as a strictly northern bird, but a few years ago a checklist and count of waterfowl on Clark Hill Lake included a few dozen common loons.  I didn’t know they spent winters in wetlands across the south and have never seen one.  They’ve been reported from many counties in Georgia but are most numerous near the coast where small fish are always plentiful.

Counties in Georgia where common loons have been sighted.  The map should include Lincoln County where they’ve been seen on Clark Hill Lake. The common loon winters in Georgia but doesn’t nest here.  Its present day nesting grounds were under glacial ice during much of the last Ice Age.  Did it nest in Georgia then?

During the Ice Age the present day nesting range of the common loon was under glacial ice.  They must have nested farther south then.  The region between the southern lobe of the Laurentide glacier and the Ohio River may have had numerous small lakes created by meltwater pulses which flooded low lying areas.  Perhaps this is where they mostly nested then.  It’s possible they nested and lived year round in the southeast during the Ice Age.  The overall population probably increased as the glacier receded and opened up more favorable habitat in the north, and they eventually abandoned their southern breeding grounds, though they still return to take advantage of ice free feeding opportunities during winter.

Attached Image: Carpometacarpus, Com. Loon.jpg

A loon fossil (looks like an intact wing) found in Florida by a member of the Fossil Forum.  This is a nice specimen. Did they breed and nest in Florida then or was it just spending the winter?

Three other species of loons spend winters in Georgia.  The red-throated loon (Gavia stellata) has been reported from 19 counties; the Pacific loon (Gavia pacifica) has been reported from 4 counties; and the yellow-billed loon (Gavia adamsii) is a rare accidental reported from only 1 county.

 

 

 

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The Nature of Paleolithic Art by R. Dale Guthrie

January 25, 2012

I recently finished reading The Nature of Paleolithic Art by R. Dale Guthrie.  Dr. Guthrie also authored Frozen Fauna of the Mammoth Steppe and dozens, perhaps hundreds, of articles for scientific journals, many of which I’ve read.  It took me almost a month to read The Nature of Paleolithic Art because it’s 500 pages and has small print and numerous pictures on every page that are worth careful examination.  The book is a brilliant creation, taking decades of research and writing to complete.  It’s well-written and the line drawings replicating the cave paintings show Dr. Guthrie is a talented and patient artist.  Because I can’t live in the Pleistocene as I so often fantasize on this blog, I wanted to get inside the heads of the humans who actually did.  Dr. Guthrie does this with his detailed analysis of their art.  Most books about paleolithic art have been written by art historians, anthropologists, and archaeologists, but this book is the first written from the point of view of a vertebrate paleontologist, making it unique.  I noticed amazon.com didn’t have much information about this book, so I will remedy this with a chapter-by-chapter review.

The first chapter is entitled “Drawn from Life.”  It consists of a discussion of how this work compares to others on the subject.  This is where Dr. Guthrie introduces one of the important themes of his book: Most paleolithic art was drawn realistically and the images were not representations symbolizing magic or religion, a view held by many anthropologists.  I agree with Dr. Guthrie.  To me this seems rather obvious–too many scholars look for something deep and complex when there is a much simpler explanation.  The people living in Europe then depended on hunting and that is what they depicted.  This chapter also covers the ecology of Pleistocene Europe.  Humans lived on the ecotone between southern European forests and the vast mammoth steppe that stretched from the British Isles to Alaska.  And there are detailed descriptions of cave geology, preservation, and taphonomy.

The second chapter is “Paleolithic Artists as Naturalists” which was perhaps one of the most interesting for me (well…that and the sex chapter).  He finds usable information about extinct species and extirpated subspecies from cave paintings.

Page from The Nature of Paleolithic Art.  The top drawings depict the most common large mammals living in Eurasia during the Pleistocene including Woolly mammoths, woolly rhinos, Megaloceros–a giant extinct deer, elk, caribou, aurochs–wild cattle, bison, musk-oxen,  horses, asses, ibex, sable antelope, cave bear, brown bear, lions, hyenas, wolves, and humans.

For example the cave paintings inform us that European lions had no manes, and horses in southwestern Europe had some striping, an adaptation for living in brushy habitat.  Dr. Guthrie shows the reader how the cave paintings represent real animal behavior–there are depictions of mating and flight response.

Chapter 3 is “Tracking down the Pleistocene Artists.”  Dr. Guthrie conducted a study that analyzed the hand prints on the cave walls.  Statistical differences between age and sex exist in the measurements of finger and palm size.  The cave painters made the hand prints by spitting a mouthful of red ocher over their hands.  Based on hand measurements, Dr. Guthrie determined most but not all the cave painters were boys aged 12 and under.

A statistical analysis of hand measurements suggests most the cave painters were boys aged 12 and under.  The kids making the hand prints were likely the same kids who were drawing the animals.

Although many cave paintings are masterpieces, most look like something a third grader might doodle.  The highest quality paintings are famous, but they’re vastly outnumbered by little known drawings that were done by less talented or less experienced artists.

It’s no coincidence that nearly every cave with paleolithic art was discovered by teenaged boys.  During the paleolithic just like in the present time, adventurous boys would be the most likely members of society to venture into caves.  Because life expectency was so low then, children made up a bigger percentage of the population then than they do now and teenaged boys would have been a significant segment of society.  Contrary to popular belief, paleolithic people didn’t live in caves but inhabited open air sites, temporary huts, and rock shelters.  This explains why most of the cave artists were young boys.

Chapter 4 is “Testosterone Events and Paleolithic Imagery.”  This one is about the evolution of human behavior and art.  He explains the evolutionary reason why paleolithic men and women differed in the partition of labor and why modern politically correct attitudes stifled early studies on the role evolution played in making men the hunters while women were better able to perform tedious tasks such as sewing clothes.  Younger men with higher levels of testosterone than women took more risks when hunting and were also more likely to explore caves.  Accordingly, the art on caves is more representative of a young male’s point of view.  Much information about women’s contributions is missing–the clothes they made are organic and long gone.  Boys painting on cave walls rarely drew people wearing clothes, even though they must have, considering the harsh climate.  There are rare exceptions.  The few pictures depicting clothes show paleolithic people wearing parkas, hoods, and boots.

Chapter 5 is “The art of Hunting Large Mammals.”  Dr. Guthrie begins by reviewing the evolution of hunting behavior in hominids.  He uses evidence from physiology, sociobiology, ecology, and accounts from the ethnographic record to show that hunting was a driving force in human evolution.  He believes hunting created the modern social bond between man, wife, and child.

Incidentally, Dr. Guthrie believes the red spots on some cave paintings of Pleistocene horses represent the tracking of blood from wounded animals.  This is an alternative explanation for the ones I gave in a previous blog entry– https://markgelbart.wordpress.com/2011/12/02/pleistocene-spotted-horses/

Another page from the book.  These are line drawings of cave paintings.

The chapter on hunting is a long one covering paleolithic weapons, the use of disguises, tracking wounded game, and harpooning fish.

Chapter 6 is “Full-figured Women in Ivory and Life.”  He explains the common depiction of full-figured fat women represents the female sex when they were most fertile. In most hunter-gatherer societies, women are rarely fertile due to a combination of environmental stress and the care of an already existing baby or toddler.  Women were most likely fertile during times of plenty when they had no young children nursing.  Men evolved to identify when women were most fertile.  And, of course, young boys drew pictures on cave walls and sculpted the famous figurines because women with big boobs and big butts were what was constantly on their minds, along with hunting large mammals.

Dr. Guthrie doesn’t go so far as to suggest the possiblity that the Venus of Willendorf represents sex slavery as I did in a previous blog entry– https://markgelbart.wordpress.com/2011/10/14/the-venus-of-willendorf-pleistocene-sex-object/

But he does dismiss the notions they represent fertility or goddess cults.

I don’t agree with Dr. Guthrie when he writes that paleolithic people chose their mates carefully.  The population was so low then that people probably had a hard time even meeting members of the opposite sex who were not related to them, and they had to accept what they could get.

Paleolithic people had many sexual items and enjoyed practices we consider modern.  Cave paintings prove paleolithic women wore lingerie.  Many cave paintings depict buxom women wearing nothing but bracelets, belts, and boots.  Paleolithic dildoes (made of stone) are very common.  One broken sculpture suggests they played bondage games.

Chapter 7 is “The Evolution of Art Behavior in the Paleolithic.”  Here, he discusses the evolution of play and how art is an extension of play.  Art contributed to the survival of paleolithic people because it helped make their brains more creative which did have practical uses.  Creativeness is heritable.

Chapter 8 is “Bands to Tribes.”  Very little paleolithic art is abstract, but the development of agriculture led to an increase in the use of abstract symbols in art.  Humans needed to invent abstract symbols to account for stored foodstuffs.  Agricultural civilization changed the human experience but not all for the better–humans suffered more malnutrition from starch-based diets, they contracted diseases spread from domesticated animals, and they experienced more warfare from being in economically unequal societies.  Not a single paleolithic drawing known depicts a shield or warfare, though individual man on man violence was rarely drawn.

Chapter 9 is “Throwing the Bones.”  This was the only chapter I found uninteresting.  It’s about the evolution of the belief in the supernatural.  There’s not enough concrete evidence left about early human’s supernatural beliefs, making this part of the book too vague and unnecessarily long-winded.  That’s really the only negative criticism I have of the book.  Sometimes, Dr. Guthrie overwrites and gives 5 or 6 examples when 1 0r 2 would have been enough.  Otherwide, I enjoyed the book very much.

The Interglacial Invasion of Warm Climate Species into Southeastern North America

January 21, 2012

Humans have been enjoying a relatively stable warm climate phase for roughly 11,000 years now–a period of time known as the Holocene.  We’ve probably been experiencing an interglacial because it’s likely we’re between Ice Ages, although with the extraordinary release of CO2 from industrial activities, there’s no telling when the next Ice Age will occur.  This phase of warm stable climate has allowed agriculture to flourish.  If climate had remained unstable and as cool as it did during the last Ice Age, civilization as we know it may never have come into existence.

The most recent interglacial previous to the present one was the Sangamonian Interglacial which lasted from 132,000 BP-118,000 BP.  Climate during the Sangamonian was even warmer than that of today.  At one point during this interglacial the north polar ice cap completely melted and sea levels were higher than they are now.  Cypress swamps grew as far north as Illinois, alligators swam in rivers flowing through what today is Missouri, and giant tortoises roamed the ridge and valley region of the southern Appalachians.  This wasn’t the warmest era in geological history–it wasn’t even close to as warm as much of the Pliocene, Miocene, Oligocene, etc. ages–but it was unusually warm compared to most of the Pleistocene.  This prolonged warm climate phase allowed many frost sensitive species of vertebrates to colonize much of southeastern North America, at least temporarily.  But because cold phases of climate during the Pleistocene lasted 10 times longer than warm phases, fossils of these tropical and subtropical species are in some cases extremely rare.  There are probably more species than the following pictorial cavalcade illustrates, but these are the ones confirmed by science.

Eremotherium laurillardi, the largest ground sloth to ever live in North America, grew to 18 feet long and weighed up to 3 tons.  Fossils of this species are quite common along Georgia’s coastal fossil sites which mostly date to the Sangamonian and early Wisconsinian.  Cold climate eventually drove them from what is now Georgia, but they persisted in Florida until maybe 30,000 BP when the beginning of the LGM became too cold for them even there.  They did continue to live in South America until 10,000 BP when hunting Indians likely drove them to extinction.  If it wasn’t for man, they may have recolonized the gulf coast of today.  2 species of ground sloths (Jefferson’s and Harlan’s) were able to survive in North America during the Ice Age, but Eremotherium must have been incapable of tolerating frosts.

Evidence that the South American marsh deer (Blastoceras dichotomous) once lived in the southeast comes from 1 mandible found at Saber-tooth Cave in Florida.  It was given the scientific name, Blastoceras extraneous, but was likely the same species populating the present day South American pampas.  Dr. Richard Hulbert expressed doubt in his book, The Fossil Vertebrates of Florida, that this mandible was correctly identified, but that was before he himself indentified the presence of collared peccaries in the Florida Pleistocene–a big surprise.

Collared peccaries were only identified from the Florida Pleistocene within the last few years.  Apparently, they colonized the south during the Sangamonian and probably other interglacials.  2 other species of peccaries–the flat-headed and the long-nosed–did commonly occur in the south during cold stages as well.

1 ocelot specimen from the Florida Pleistocene proves this cat lived in the south.  It seems that this cat should be able to survive in Florida today.  I suspect Indians coveting its spotted coat led to its demise there.

Fossil evidence of a small species of cat resembling the modern day margay comes from Florida and 2 widely separated sites in Georgia–Ladds and the Isle of Hope site.  Scientists are uncertain of the identification–it’s either a margay,  jaguarundi, or a distinct extinct species.  Despite the scientific genus name, Leopardus, it’s not at all closely related to a leopard.  Was it climate or paleo-Indian desire for spotted coats that restricted this species to isolated jungles?

Giant tortoise fossils dating to the Pleistocene were found at Ladds, the northernmost locality, though during the Pliocene, which was mostly warmer than the Pleistocene, they lived as far north as Kansas.  In contradiction to what most scientists think, I suspect giant tortoises were capable of surviving light frosts.  See my reasoning in a blog entry from my April 2011 archives.

In the Sangamonian of Georgia I suspect alligators may have ranged into the Etowah River.  If giant tortoises lived in the area, alligators surely must have been able to live there too.

Many species of South American and Central American birds also extended their range north in Sangamonian times.

Pleistocene Fossil Felid Ratios from the University of Florida Database

January 16, 2012

I followed the same procedure from last week’s study but counted the number of cat fossils in the University of Florida’s Natural History Museum database instead of dog fossils.  I only counted fossils dating from the Rancholabrean Land Mammal Age 300,000 BP-11,000 BP.  The results may be off a little because I was scrolling down while looking at a computer screen.  The results may also be misleading because many specimens may come from just 1 individual.   Nevertheless, I think the data reveals a good estimate of the ratio of species composition during the Pleistocene.

Listed on the University of Florida Museum of Natural History database, I counted 46 jaguar (Panthera onca) specimens, 21 giant panther (Panthera atrox) specimens, 42 saber-tooth (Smilodon fatalis) specimens, 6 scimitar-tooth (Dinobastis serum) specimens, 41 cougar (Puma concolor) specimens, 46 bobcat (Lynx rufus) specimens, 12 river cat (Leopardus amnicola or weidii) specimens and 1 ocelot (Leopardus pardalis) specimen.

The results are similar to those reported by the amateur fossil collectors who post on the fossil forum.  The most significant difference between their reports and database information is abundance of jaguar to saber-tooth abundance.  Amateur fossil collectors claim jaguar fossils are much more common in Florida than saber-tooth, though they do collect the latter and some have found scimitar-tooth specimens as well which are rare in the database.  It may be that the UF database includes a skeleton of a saber-tooth accounting for multiple specimens from 1 individual.

Dire wolves accounted for 64 specimens in my previous study, making them 33% more common, at least in the fossil record than any single species of big cat.  Overall, big cats combined outnumbered dire wolves 156 to 64, making large felines more than twice as common as dire wolves.  Perhaps there was less competition among species of canids, but more among felids.

Pleistocene habitats favorable to various species of big and small cats varied widely.  Mesic oak forests and cypress swamps, which expanded during warm interglacials and interstadials, favored jaguars, river cats, and ocelots.  Jaguars are adabtable enough to live in desertlike brush conditions which were common during cold arid stadials.  Cougars and bobcats thrive in many different types of environments.  The exact environments favored by giant panthers, saber-tooths, and scimitar-tooths is unknown, but it’s likely they were capable of adapting to many different ecotones.

Saber-tooths were evidently one of the most common large carnivores south of the ice sheets in North America.  They were actually no larger than a modern day jaguar.  Saber-tooths never colonized Eurasia, but a distant cousin, the scimitar-tooth had close relatives that did live from the southern tip of Africa to Alaska.  Scimitar-tooths also had longer front legs but these were more slender than those of the saber-tooth.  Their fangs were also smaller and more curved.  In Africa, Asia, and Europe scimitar-tooths became extinct much earlier than saber-tooths did in America.  I suspect they never learned to fear man, explaining their earlier extinction.  I suggest fanged cats didn’t often back down from anything.  Scimitar-tooths probably colonized southeastern North America during stadials when grasslands expanded due to dry climate which in turn caused an increase in the populations of ungulates. 

Giant panthers probably resembled large maneless lions.  True lions did live in Alaska and across Eurasia.  But south of the ice sheets in North America, the common ancestor split into 2 different species–Panthera atrox and Panthera onca.

8 cat 10 Biggest Cats in the History

This image comparing Pleistocene jaguars with modern jaguars may be a slight exaggeration, but jaguars did grow bigger during the Pleistocene because they preyed on larger mammals and had more competition among carnivores.

I’ll write more about the presence of margays and ocelots in Pleistocene Florida in my next blog entry.

Here are some related articles about big cats from my archives.

“Panthera atrox! What Kind of Cat was it?”– https://markgelbart.wordpress.com/2010/07/28/panthera-atrox-what-kind-of-cat-was-it/

“Why did fanged cathttps://markgelbart.wordpress.com/tag/saber-tooth/s have sloping backs and large forelimbs?”–

“Two new studies of saber-tooths.”– https://markgelbart.wordpress.com/2011/07/08/two-new-studies-of-sabertooth-smilodon-fatalis-anatomy/

“Cougars vs. jaguars”–https://markgelbart.wordpress.com/2010/07/08/cougars-vs-jaguars/

Pleistocene Fossil Canid Ratios Recorded in the University of Florida Database

January 11, 2012

The abundance of Pleistocene fossil sites in Florida has allowed the university in Gainesville to become a center of information for other scientists.  Scientists excavating new fossil sites use existing fossils at the University of Florida Museum of Natural History to help identify the new specimens they pull from the earth.  It’s not always easy to differentiate closely related species–the subject of this blog entry, the canids, are notoriously difficult to distinguish.  Vertebrate zoologists and paleontologists measure and describe every part of every bone and tooth when examining new specimens.  They publish this information in scientific journals and accumulate knowledge of the size limits and shape variations of a particular species’ anatomy.  If a newly discovered fossil tooth for example doesn’t fit any known pattern of shape or size, than scientists suspect they may have discovered a new species.  The more data scientists have, the better able they are to identify new species and spot evolutionary trends over time within a species.

Fossil collecting is popular in Florida, thanks to all the sinkhole lakes and caves with basal chemistry in the soil that preserves bones.  Amateur fossil collectors have many more fossils in their collections than the University of Florida’s Natural History Museum..  Many are for sale as well.  It would be a great benefit to science, if collectors made arrangements to donate their collections to the museum upon their deaths.  Many valuable specimens have been lost when their owners die and family members, not interested in the subject, lose track of where they put the old bones.

My little study is limited to canid fossils listed on the University of Florida database and leaves out the great many more in the hands of amateur fossil collectors.  I also limited this survey to the Rancholabrean Land Mammal Age (300,000 BP-11,000 BP), leaving out Armbruster’s wolf which dominated the middle Pleistocene before being replaced by dire wolves.  Nevertheless, I think there’s enough information to suggest relative canid species abundance during the late Pleistocene.  Keep in mind, I was counting on a computer screen while scrolling down, so my numbers may be off slightly.

Listed on the Florida Museum of Natural History’s database, I counted 64 dire wolf (Canis dirus) specimens, 34 coyote (Canis latrans) specimens, 1 red wolf (Canis niger) specimen, 9 domestic dog (Canis familiaris) specimens, 0 dhole (Cuon alpinus) specimens, and 55 gray fox (Urocyon cineorgenteus) specimens.

The fossil record strongly suggests that from 300,000 BP to about 11,000 BP dire wolves were by far the most common large canid being about twice as abundant as coyotes.  Red wolves were rare but present.  Gray foxes were just as common during the Pleistocene as they are today.  These neat little foxes have the ability to climb trees, a skill that saves them from their larger relatives.  There is no evidence of dholes but as I wrote in a previous blog entry http://markgelbart.wordpress.com/2011/06/01/did-the-dhole-cuon-alpinus-range-into-southeastern-north-america-during-the-pleistocene/ , I suspect they may have periodically colonized parts of the southeast but in numbers too low to leave fossil evidence.

Dire wolves were the dominant large canid in the southeast (and all across North America south of the Ice Sheets) during the late Pleistocene.

Coyotes probably occupied a niche similar to African jackals.

Gray foxes thrived in areas where they had access to trees and could escape larger predators.

The presence of domesticated dogs in the Pleistocene fossil record puzzled and surprised me.  I almost didn’t even do a database search for Canis familiaris and only did so as an afterthought.  Most anthropologists don’t think humans domesticated dogs until after the Pleistocene about 10,000 years ago, but the fossil evidence contradicts this.  In fact scientists recently discovered the skull of a domesticated dog in a Siberian cave that dates to 33,000 BP.  They determined  this particular domesticated dog was not the ancestor of the lineage that led to today’s dogs but instead its descendents died out.  It’s probable that there were many early lineages of domesticated dogs that ceased to exist for various reasons.  Perhaps that group of people died out or stopped keeping dogs.  The popular idea that people domesticated dogs by kidnapping and raising wolf pups is a misconception.  Scientists think it’s the other way around–dogs adopted us.  Dogs are descended from the wolves which had the least flight response.  Wolves that hung closely around human campsites for access to leftovers gave birth to pups with floppy ears, multi-colored coats, and other dog traits that differentiate them from other wolves.  The gene for tameness shares a pathway with the gene for these physical characteristics.  So it’s likely that dogs adopted people in many different geographic locations wherever wolves (Canis lupus) began occupying areas adjacent to human campsites.  Obviously, dogs either followed or were brought to Florida by the Paleo-Indians.

The authors of a chapter in the book The First Floridians and the Last Mastodons suggest that all the coyote fossils found in Florida are actually domesticated dog fossils, but they only knew of a handful of coyote fossils.  Apparently, they didn’t know 34 specimens had been found.  I doubt scientists made that many misidentifications.

Dire wolves succeeded in becoming one of the dominant predators in the environments of southeastern North America where they found a wealth of prey roaming the open woodlands and savannahs.  Everything from bison and horses to deer and rabbits sustained them, and a mammoth or mastodon that died of natural causes provided a feast.  Coyotes successfully co-existed with dire wolves by scavenging large predator kills and by hunting rodents.  Red wolves must have been restricted to islands and perhaps deeply wooded swamps where they could survive on deer and small game.  Their niche must have been areas with lower densities of prey as opposed to grasslands that hosted large herds of ungulates.  Following the extinction of the megafauna and dire wolves, forests replaced grasslands and red wolves increased in number and drove coyotes completely out of the south.  But after European settlers wiped out the red wolves, coyotes returned.

References:

Ovodov, Nikolai, et. al.

“A 33,000 Year Old Incipient Dog from the Altai Mountains of Siberia: Evidence of the Earliest Domestication Disrupted by the Last Glacial Maximum”

Plos One 6 (7) 2011

http://www.flmnh.ufl.edu/databases/vp/intro.htm

The Dunwoody Nature Center

I attended my nephew’s bar mitzvah in Dunwoody, Georgia last weekend.  Dunwoody consists of dozens of subdivisions and plenty of shopping centers and absolutely no rural farmland.  I didn’t hold out much hope for a nice nature walk here–the traffic is terrible.  But at least the developers left a lot of trees standing.  I decided to walk from my sister’s house to a little park known as the Dunwoody Nature Center and I discovered a surprising gem.

This white oak was about 4 feet in diameter.  White oak is a common tree in Dunwoody.

From the composition of the trees left standing most of Dunwoody must have once hosted a pretty nice dry upland forest.  Too bad developers converted it into a crowded suburb.  Today, white oaks, black oaks, southern red oaks, shortleaf pines, and loblolly pines are the dominant trees.  The Dunwoody Nature Center slopes sharply down toward Wildcat Creek, the name of which is a relic to its former status as a wilderness.  The woods here are dominated by beech, white oak, sweetgum, river birch, and loblolly pine.  I was stunned to see a woodlot of mostly beech trees in central Georgia.

A mature beech tree growing on the edge of a rocky creek.  It’s surrounded by many immature beech saplings.

Fossil pollen studies show beech was a common tree in the south during the end of the Ice Age when the Laurentide glacier began melting and releasing more moisture in the atmosphere creating a climate that was still cool but more rainy than it was during the height of the Ice Age.  The presence of abundant beech in the fossil record is indirect evidence of massive flocks of passenger pigeons.  Passenger pigeons fed on acorns–in some places completely eliminating the oak seed crop…and the beech’s competition.  Although beech trees produce an edible nut, they can also spread from roots and could survive their seed being consumed by passenger pigeon flocks.  Since the passenger pigeon’s demise, oak forests have been replacing beech forests in many areas.  So I was delighted to see this remnant beech forest in central Georgia.

Wildcat Creek flows through a granite outcropping.  Here is a miniature waterfall.

Two little league baseball fields take up about half the space of the park.  The park is heavily used by dog and toddler walkers.  It’s popularity shows that the planning commission in charge of developing Dunwoody should have arranged for the purchase of more land for more parks.

When did the Fisher (Martes pennanti) Last Roam the Wilds of Georgia?

January 6, 2012

Another interesting mammal with northern affinities that used to range into what’s now Georgia is the fisher (Martes pennanti).

I found this photo of a fisher carrying a dead squirrel on google images but I think it’s from the cover of an issue of the Journal of Heredity.   They had an article about genetic bottlenecks of this species created from habitat fragmentation.  Fishers require complete forest cover and avoid open fields.

Fossil evidence of fishers in Georgia comes from Ladds stone quarry in Bartow County.  Ladds is a collapsed and eroded cave system that yields fossils of warm climate species such as giant tortoise, Florida muskrats, and rice rats; and c0ol climate species such as bog lemmings and meadow jumping mice, besides the fisher.  The warm and cool climate species may or may not have occurred during the same climate phase–the quarry operation may have mixed fossils of different ages together.  But asymmetric compositions of species are common in most other Pleistocene fossil sites, so no one is really sure.  The fossils found here are at least 10,000 years old.  I suspect they date to the Sangamonian Interglacial–more than 100,000 years ago for reasons I discuss in my blog entry, “The Giant Chipmunk (Tamias aristus).  Kicked up Version of the Eastern Chipmunk?” https://markgelbart.wordpress.com/2011/01/20/tamias-aristus-the-extinct-kicked-up-version-of-the-eastern-chipmunk/

The fossil material of the fisher found at Ladds consisted of a couple of fragments of cheekbone with teeth attached and a partial jawbone.  This proves that fishers occurred in Georgia thousands of years ago during the Pleistocene.  What is not known for sure is how recently they lived in state.  There is fossil evidence of both porcupine and fisher from the Law’s archaeological site ins northern Alabama which dates to about 1700 AD, and from the Etowah Indian Mound Site in Bartow County which dates to between 1100 and 1500 AD.  This doesn’t prove fishers lived in Georgia that recently.  Indians traded fisher pelts and porcupine quills, and they could have originated from their known historical range.  However, it’s quite possible fishers had a more southerly range within the last few hundred years and were trapped out by Indians selling pelts to newly available European fur markets. 

Historical range of the fisher.  They may have ranged further south but were uncommon and trapped out early after European contact.  During the Ice Age just about their entire modern range was under miles of glacial ice, so of course they once ranged further south in pre-historic times.

Ecological studies show fishers require continous tracts of mature forest, and they completely avoid open areas.  In New England now that fur trapping has gone out of style and forests are growing back, fishers are recolonizing states where they’ve been long absent.  They’ve got a long way to go before they reach Georgia though.

Fishers prey on squirrels, rabbits, mice, and birds.  Studies of their dietary habits have yet to find fish in their scat, so their name is misleading.  They’re one of the few carnivores that commonly prey upon porcupines, but they occasionally die from injuries suffered when they mishandle the spiny rodents.  They kill the porcupines by biting their faces off, not by flipping them over as is falsely believed.  Fishers will kill small house dogs and cats, but I don’t believe reports that they attack German Shepherds.  Fishers only weigh 10-15 pounds and would have a size advantage over smaller cats and dogs but a big dog could shake a fisher and break its back.  Scientists studying Canadian lynx report two cases of fishers feeding upon radio-collared cats.  I don’t believe a fisher can kill a full grown lynx.  In one instance there was no sign of a struggle in the snow which tells me the cat was already dead.  A fisher doesn’t have a powerful enough bite to kill a large animal instantly, precluding the possibility that it ambushed a sleeping cat.  I think the cat died of either sickness or starvation.  Likewise, a find of bobcat in fisher scat was probably from a kitten or an already deceased cat.  The following youtube video shows a fisher struggling to kill a gray fox.  Bobcats and lynx are much more powerful than gray foxes.  The former regularly preys on gray foxes.  (Note: The fox in the video is a gray fox, not a silver color phase of a red fox.)

http://www.youtube.com/watch?v=txdoUgli2FQ

When I visited the Silver Bluff Audubon Center a month ago, I heard a cry that sounded like the distress call of the gray fox from this video.  At the time I didn’t know what it was and thought I was hearing a bird I couldn’t identify.  Maybe I was hearing a gray fox being attacked by coyote or bobcat.

Caribou (Rangifer tarandus) in Pleistocene Georgia

January 1, 2012

It always fascinates me that caribou used to roam what’s now Georgia. The presence of caribou in the Pleistocene south is confirmed from fossil finds in Yarbrough Cave, Bartow County, Georgia; Bell Cave in northern Alabama; Charleston, South Carolina; and at least 3 sites in Tennessee–Baker Bluff Cave, Beartown Cave, and Guy Wilson Cave.  Caribou fossils have not been found in the abundant fossil sites in Florida, so its southernmost range limit occurred somewhere along a line drawn through what’s now middle Georgia, South Carolina, and Alabama.  The present day range of eastern woodland caribou was completely under glacial ice during much of the last Ice Age, so of course, they must have ranged further south.

What a majestic beast.

I have some questions about caribou in Pleistocene Georgia that I suppose may never be answered.  Were they year round residents or did they migrate here seasonally?   Today, barren ground caribou are known for their long distance migrations, but eastern woodland caribou are reported to stay in the same area their entire lives.  Did caribou live in the south during cold phases of climate or were they here during interstadials as well.  The caribou fossil from Charleston, South Carolina comes from strata thought to date to a warm interglacial.  There is a scientific method that can be used to answer the first question.  So far no scientist has chosen to chemically analyze the tooth enamel of fossil bones of southern caribou.  By determining the strontium isotope ratios in the tooth enamel they can compare it to that of extant mammals and mathmatically estimate where the extirpated southern caribou spent their time.  Scientists have used this technique with mastodons and mammoths.  Scientists determined from mastodon fossils found in Florida that they had spent time in central Georgia, but mammoths in Florida did not migrate long distances.

Robert Martin, a professor at Murray State and author of Missing Links: Evolutionary Concepts and Transitions in Time, first identified two caribou molars from Yarbrough Cave.  In an email he informed me there was also unsorted material from the cave but was unclear whether this consisted of more caribou specimens.  Murray State donated all of the fossils to the Florida Museum of Natural History where they probably rest in the bottom of a basement drawer.  The original fossil discoveries were made in 1991 but they have yet to be described in detail in the scientific literature with the exception of a few teeth of southern bog lemmings.  I had to ask Dr. Martin which parts of the caribou they found in the cave. 

Caribou are the only member of the deer family that have antlered females.  Male caribou shed their antlers after the rut is over, but females retain theirs through the winter.  The females dig craters in the snow, exposing lichen and grasses–their food supply.  They defend these territories against other females and antlerless males.  The females with the biggest antlers have the best chance of maintaining their top condition for next year’s pregnancy, and it improves the survival rate for the present year’s calf.  In regions with light snows where it’s unnecessary to dig craters, female caribou have smaller or no antlers.  Therefore, southern female caribou probably had smaller antlers.

For most of the year cow caribou fear or are antagonistic toward bulls.  During the rut the bull caribou approach the cows by lowering their head and bleating like a calf approaching to nurse.  (This reminds me of human foreplay–tit sucking.)  The female will stop and urinate, and the male will smell the urine to test whether she’s in estrus.  The vomerosonal organ in the nostril is used to detect the pheremone levels.  Primates lost this organ along their evolutionary pathway, but humans still wrinkle their noses at funky odors.

Reindeer warble fly.  They lay eggs under the hides of caribou.  Eskimos enjoy eating the larva–a fatty, salty snack, according to R. Dale Guthrie.  Reindeer meat is lean, and the average human would starve on such a high protein diet with no fat.  The warble fly larva provided valuable fat for people living in the Pleistocene.  Reindeer warble flies must have expanded their range into Georgia during the Ice Age.

Reindeer warble flies (Oedenagena tarandi) torment caribou all summer.  Their larva live under the hide during the winter and emerge during the spring.  Caribou meat is a healthy source of protein but is so low in fat that most humans would starve to death if they only ate this kind of meat.  Eskimos and Pleistocene Europeans eat or ate the warble fly larva which is high in fat.  It’s a valuable dietary supplement.  Warble fly larva is even depicted in paleolithic art alongside the more famous cave paintings of mammoth, bison, and horses.  Reindeer warble flies almost certainly enjoyed an expanded range during the Pleistocene and flew in Georgia then.

Yarbrough Cave

The area around this cave is clear cut, and the owner would “just as soon fill the cave in or level it.”  Many real estate developers are ignorant Nazis whose God is money.

View from inside the cave.

Yarbrough Cave is a small one about 120 feet long with a couple of small side passages.  Some woodland Indian artifacts have been excavated here.  All of the Pleistocene fossils in this cave come from a surprisingly small area–a 5 foot square, 6 foot deep hole in a side passage known as the Peccary Room.  The fossils date from between ~15,000 BP-~ 19,000 BP (from 2 different specimens), the end stage of the Last Glacial Maximum.  Like most other Pleistocene fossil sites in Georgia, the species represent a variety of habitats that must have existed nearby–woodlands, grasslands, and wetlands.  13-lined ground squirrels require extensive treeless prairies, but the other 6 species of squirrels show that forests must have been predominant.  Beaver, muskrat, river otter, and raccoon prove wetlands occurred here as well. Many more microfossils were lost here when some nameless blundering scientist botched the removal of a large section of matrix.  He probably lost all the bird bones.  There’s probably more fossils to be found here with a little digging and as I mentioned earlier the fossils already found here have yet to be described in detail.  Anyway, here’s the list of Pleistocene fossils that were excavated from Yarbrough Cave between 1988-1991. * denotes extinct species

short tailed shrew–Blarina brevicauda

least shrew– Cryptotis parva

eastern mole–Scalopus aquaticus

eastern pipistrille-Pipistrelus subflavus

big brown bat–Eptesicus fuscus

*giant ground sloth (probably Harlan’s)–Megalonychid sp.

*beautiful armadillo–Dasypus bellus

rabbit sp.?–Sylvilagus sp.

eastern chipmunk–Tamias striatus

13-lined ground squirrel–Spermophilus tridecemlineatus

red squirrel–Tamiasciurus hudsonicus

gray squirrel–Sciurus carolinensis

fox squirrel–Sciurus niger

southern flying squirrel–Glaucomys volans

northern flying squirrel–Glaucomys sabrinus

woodchuck–Marmota monax

beaver–Castor canadensis

mouse sp.?–Peromyscus

wood rat–Neotoma floridana

pine vole–Microtus pinetoreum

*?steppe vole–Microtus sp.

meadow vole–Microtus pennsylvanicus

muskrat–Ondatra zibethicus

southern bog lemming–Synaptomys cooperi

meadow jumping mouse–Napeozapus insignis

dire or timber wolf–Canis dirus or lupus.  The preliminary report says the fossil material compares favorably to the latter but tooth size overlaps between the 2 species  and I bet it’s from the former.  Ronald Nowak, the world’s foremost authority on Pleistocene canids, doesn’t think timber wolves ever colonized the southeast.

black bear–Ursus americanus

raccoon–Procyon lotor

weasel sp.–Mustela

striped skunk–Mephitis mephitis

river otter–Lutra canadensis

cougar–Puma concolor

bobcat–Lynx rufus

*long-nosed peccary–Mylohyus nasatus

*flat-headed peccary–Platygonus compressus

white tail deer–Odocoileus virginianus

caribou–Rangifer tarandus

References

Guthrie, R. Dale

The Nature of Paleolithic Art

The University of Chicago Press 2006

Martin, Robert

“A Preliminary List of Late Pleistocene Mammals from the Peccary Room of Yarbrough Cave, Bartow County, Georgia”

Palidicola 3 (2) 33-39 May 2001

http://www.forums.caves.org/viewtopic.php?f=8&t=5308