Posts Tagged ‘Florida spectacled bear’

The Inner Space Cavern Fossil Site near Georgetown, Texas

August 18, 2016

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

Location of Georgetown, Texas

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

Inner Space.

View inside Inner Space Cavern.

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

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

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

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

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

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

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

Reference:

Sansom, Jones; and Ernest Lundelius

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

Austin Geological Society Bulletin 2005

Bearzilla: The Biggest Bear in History

December 10, 2012

With a massive presence and a terrifying roar Arctotherium angustidens rampaged over South America about 2 million years ago, chasing frightened predators away from their kills and gorging itself on the scavenged meat.  These giant bears reached a weight of 3500 pounds, so to sustain this bulk, they needed to eat approximately 50 pounds of meat per day.  They occasionally captured wounded or sick prey animals, and they likely consumed some vegetable matter, but their primary survival strategy was “kleptoscavenging.”  Like their distant North American cousins, the giant short-faced bear (Arctodus simus), Arctotheriums trotted long distances, covering grand territories, and with their keen sense of smell they could detect the scent of blood from miles away.  They followed their nose to the source and used their great size to intimidate big cats, wolves, and terror birds from the meat those successful carnivores had worked so hard to procure.

Size comparison between Arctotherium angustidens and Homo sapiens.  This was probably the biggest species of bear in earth’s history.

The bones of an old male Arctotherium were discovered in 1935 during the construction of an hospital in La Plata, Argentina.  The skeleton was not described in the scientific literature until 2010.  The scientists re-examing the specimen determined the individual suffered and recovered from several injuries, likely incurred from battling other male bears.  The old bear also had arthritis.  From the bones they estimated a mass of 3500 pounds.

By about 800,000 BP Arctotherium angistidens no longer occurs in the fossil record.  Some scientists suggest it became extinct due to competition from other predators, but I disagree with this notion.  Instead, I think they evolved into a more herbivorous bear because of environmental changes.  A large “kleptoscavenger,” like Arctotherium, can only survive in an environment with abundant prey animals and predators.  Grasslands can support this kind of biomass, but forests don’t.  I propose that cyclical climatic conditions caused South American grasslands to convert to woodlands.  Arctotherium angistidens was forced to eat more vegetable matter in this woodland environment and eventually evolved into different species, culminating in Arctotherium wingei.  The latter species was as herbivorous as its distant cousin, the still extant spectacled bear (Tremarctos ornatus) and was adapted to live in a similar forested environment, until it went extinct at the end of the Pleistocene.

Bears, cats, and wolves invaded South America when the Central American landbridge rose above sea level 3 million years ago.  The South American versions of bears and saber-tooths initially grew larger than their North American cousins, perhaps because prey animals were larger and slower here.

Arctotherium was in the same family as the North American short-faced bears which included the giant short-faced bear (Arctodus simus), the lesser short-faced bear (Arctodus pristinus), and the Florida spectacled bear (Tremarctos floridanus).  The lesser short-faced bear was probably ancestral to the giant short-faced bear.  The giant short-faced bear was mostly carnivorous but ate some plant matter, while the spectacled bear was mostly herbivorous but ate some animal matter.  A. pristinus was more of an omnivore than the other 2 species.  Fossils of the giant short-faced bear and the spectacled bear have been found at late Pleistocene sites in southeastern North America, but the latter is far more abundant.

Photo from a 1960 issue of Sports Illustrated of the hunter standing next to the taxidermic mount of the biggest wild polar bear ever recorded.  He shot and killed it in Alaska. It weighed 2210 pounds.  This was about the average size of the extinct giant short-faced bear.

Scrape marks on the side of Riverbluff Cave, Missouri.  They are 15 feet high and were made by the giant short-faced bear.  The bear stood 12 feet tall on its back legs and must have reached up with its arms over its head to reach that height.

Size comparison between the giant short-faced bear and a Yellowstone grizzly.

As the top above photo shows, the largest wild polar bear ever recorded was shot in Alaska in 1960.  It weighed 2210 pounds.  This was only slightly larger than an average male giant short-faced bear.  I’m sure a few individuals of the latter species exceeeded that size.  They reached that great size from a combination of genetics and a high protein diet.  Scientists estimated  the giant short-faced bear required 35 pounds of meat everyday.  In environments with fewer prey animals, they may not have reached a particularly large size.  Grizzly bears (Ursus arctos) are the exact same species as the Kodiak bear.  The former average about 500 pounds, yet the latter reach weights of 1500 pounds.  Kodiak brown bears enjoy a high protein diet rich in salmon, while grizzly bears are forced to survive on roots, berries, rodents, and only the occasional scavenged kill.  A Yellowstone grizzly cub, if moved to Kodiak Island, would probably grow much larger on a diet of all the salmon it could eat than it would if it stayed in Yellowstone.  The largest brown bear in captivity grew to 2100 pounds–a mass equal to the average weight of a giant short-faced bear.  This bear had a more favorable diet in its zoo environment than it would have in the wild.

See also: https://markgelbart.wordpress.com/2011/03/10/pleistocene-bears-of-southeastern-north-america/

Reference:

Soibelzan, L.H.; B.W. Schubert

“The Largest Known Bear, Arctotherium angustidens, from the early Pleistocene Pampan Region of Argentian with a Discussion of Size and Diet in Bears”

Journal of Paleontology 85 (1) 69-75 2011

Pleistocene Bears of Southeastern North America

March 10, 2011

Nothing demonstrates wilderness more than a robust population of free roaming bears.  During the Pleistocene before people were around to kill them and destroy their habitat, there must have been tens of thousands of bears living within the boundaries of what today is Georgia.  It’s possible that 5 different species could have been found here in the same time span, though we can be more sure there were at least 3 sharing the same range.  Today, only 1 species of bear resides in Georgia–an estimated 5100 black bears still roam the mountains, the Okefenokee Swamp, the Altamaha and Ocmulgee river bottoms, and Houston County.  Occasional stragglers leave these last strongholds and raid urban dumpsters and suburban bird feeders, but these occurrences are rare.  One study of Georgia bears determined that suitable habitat can support 1 bear for every 3 square kilometers.  That means ideally, Pleistocene Georgia hosted a population of 30,000-40,000 bears.  (*Georgia is about 60,000 square miles. 1.86 square miles =3 square kilimeters.  Moreover, during stadials Georgia’s land mass increased by about 10,000 square miles due to the fall in sea level.)

Here’s a review of every known bear species that lived during the Pleistocene in southeastern North America.

Black bear–Ursus americanus

Photo from google images of a black bear in the Okefenokee Swamp.

Ursus abstruscus is the probable evolutionary ancestor of American and Asian black bears which once consisted of a geographically continuous population.  Glacial ice separated the two populations at the beginning of the Pleistocene, resulting in two different species.  Bjorn Kurten notes that Pleistocene black bears grew as large as modern day grizzlies.  I believe Pleistocene black bears were larger and fiercer than their modern day descendents because they had to survive confrontations with saber-tooths, giant panthers, jaguars, and packs of dire wolves.  Cavers and scientists discovered black bear fossils at Ladds and Kingston Saltpeter Cave in Bartow County, and the Isle of Hope Site in Chatham County.  They’re also commonly found in Florida fossil sites but only a few have been recorded from South Carolina.

Florida spectacled bear–Tremarctos floridanus

Photo of a spectacled bear, Tremarctos ornatus,  from google images.  This is the only living species from the once widespread short-faced bear family.  It is a close relative of the extinct Tremarctos floridanus.  Of course, scientists have no way of knowing whether Tremarctos floridanus was also spectacled, but they call it that anyway.

Now extinct, this was likely the second most common species of bear in southeastern North America during the Pleistocene.  Only 1 specimen has ever been recovered in Georgia (at Ladds), but its fossils have commonly been found in Florida and South Carolina.  It’s thought of as primarily a vegetarian, but a recent study of Pleistocene bears concluded that all were opportunistic omnivores that would eat anything they could obtain.  Tremarctos’s range in the late Wisconsinian Ice Age seems to have been restricted to the southeast.  During warm interglacials it expanded as far north as Kentucky.  It probably just lived in the coastal plain of Georgia and South Carolina as well as Florida during colder climatic stages.

Lesser short-faced bear–Arctodus pristinus

Photo of a fossil jaw bone of Arctodus pristinus from Additions to the Pleistocene Mammal Fossils of South Carolina, North Carolina, and Georgia by Albert Sanders.

Photo of fossil bear teeth from the above mentioned publication.

It’s unclear from the fossil record whether this species co-existed with its larger cousin, the giant short-faced bear, or was simply ancestral to it.  Its fossils have only been recovered from a few eastern sites in Florida, South Carolina, Maryland, and West Virginia.  Teeth attributed to this species overlap in size with those of Arctodus simus.  Florida fossils of this species, including those from Leisey Shell Pit, indicate this animal lived from the early to mid-Pleistocene (~1.8 million-300,000 BP), whereas giant short-faced bear fossils in Florida date to the late Pleistocene (~300,000-~11,000 BP).  However, fossils of the lesser short-faced bear were found in South Carolina sediments thought to date from the Sangamonian Interglacial (~132,000-~118,000 BP) which is also considered late Pleistocene.  These South Carolina specimens haven’t been radiometrically dated, so no one knows exactly how old they are.  Perhaps this species did survive as a relic species in some geographical locations until the megafauna extinction.  Arctodus pristinus is considered more of a general feeder; Tremarctos floridanus a more herbivorous species; Arctodus simus a more carnivorous bear.

Giant short-faced bear–Arctodus simus

Dan Reed’s photo-shopped reconstruction of a giant short-faced bear.   

The giant short-faced bear ranks up there with mammoths, mastodons, ground sloths, and saber-tooths as among one of the most spectacular creatures of this era.  Studies suggest it lived by aggressive scavenging.  It’s extremely acute sense of smell detected blood from a great distance.  Then, the beast would relentlessly trot toward the source of the appetizing odor, and its sheer size would intimidate the partially satiated carnivore that actually made the kill into surrendering the carcass.  Arctodus simus fossils are more common in western fossil sites, but a few have been discovered in the southeast, proving it did occur here, at least sporadically.  An Arctodus simus skeleton rested in the Fern Cave system in Jackson County, Alabama which borders northwestern Georgia, until it was discovered by cavers in 1970.  In addition a number of teeth from this species have recently been discovered in north Florida fossil sites, and some Arctodus simus material was also discovered in Virginia.

Grizzly bear–Ursus arctos

Photo of a grizzly bear and cub from google images.

Welsh cave in Kentucky yields grizzly bear fossils dating to about 12,000 BP.  This is the easternmost known occurrence of this species.  Grizzly bears roam hundreds of miles, so it’s likely if they lived in Kentucky then that they must have entered Tennessee.  But the lack of grizzly bear fossils in other southeastern states suggests they never penentrated the region in significant numbers.  Still, I believe a few irregular stragglers may have wandered into what’s now north Georgia.  It may be that the existence of 3 or 4 other species of bears prevented grizzly bears from colonizing much of the southeast during the Pleistocene, and then man arrived, creating another obstacle blocking their migration into the region.  Grizzly bears are a relatively recent addition to North America’s mammalian fauna, but they did live on the continent prior to the LGM, 30,000 years BP.  They’re the same species as the Eurasian and Alaskan brown bears.

If I could live in the Pleistocene (part 4).

For those unfamiliar with this blog, I occasionally fantasize living during the Pleistocene but with modern conveniences, such as an adobe house with woodstoves, solar heating, electricity, and a time tunnel that connects me to the modern world.

I’ve thought of a simple way to observe bears from my abode.  Connected to my Pleistocene house is a 5 story watchtower designed in the shape of a lighthouse in which I can view the surrounding landscape.  I would take a barbecue grill to the fifth story which has a canopy but an open window stretching for 360 degrees around.  There, I would grill meats.  The aroma should attract bears and other carnivores from miles around.  A bear could potentially climb up the side of a light-housed shaped building, so I would have to have some kind of designed guards that would prevent this. 

I would avoid hunting bears, if possible.  I think modern hunters who kill bears are jerks.  I can understand why the pioneers did it.  They didn’t have grocery stores and had to eat and make use of what they could obtain.  But there is no reason to hunt bears today, unless they prove a danger to tourists.  They don’t reproduce as rapidly as deer, and it’s just not ecologically necessary to hunt them.

Bears were a valuable source of meat and fat for early settlers.  Early accounts reveal an important dish of the Indians.  The Indians frequently diced up venison (which is very lean) and fried it in bear fat.  Bear fat was also the number one source of cooking fat in New Orleans in 1800.  It was gradually replaced by lard as the settlers brought in hogs.