Alligators vs Sharks

October 15, 2017

Bloody battles between hundreds of alligators and sharks were an oddity of nature that occurred infrequently for millions of years.  Alligators are considered a freshwater species, but they do inhabit brackish lagoons and can even live in saltwater environments for weeks.  Alligators foraging near beaches normally prey on fish, shrimp, crabs, wading birds, raccoons, mink, and sea turtles.  Alligators take advantage of weather and tidal conditions that concentrate their prey in confined areas.  During the year 1877 near Jupiter, Florida a strong flood tide trapped a large number of fish in a bend of a tidal inlet, attracting an estimated 500 alligators.  The alligator feeding frenzy lasted for days, and the blood drew hundreds of sharks into the main channel of the inlet.  The current shifted and carried the alligators into the main channel where they fought sharks for hours.  Dead alligators and sharks washed ashore for days, following the battle.  It is unlikely such a spectacle could occur today.  Sharks have been overfished, greatly diminishing their population, and alligators, though on the increase, will never be as abundant as they were when Florida was mostly wilderness.  However, the primeval world was the scene of many alligator vs shark wars because they co-existed for millions of years, often competing for the same prey.  Alligators are a member of the crocodilian family.  The crocodilians evolved at least 83.5 million years ago, and the ancestors of the crocodilians, the Pseudosuchia, originated 250 million years ago.  The ancestors of the alligator’s ancestors undoubtedly came into conflict with sharks.  It’s an ancient rivalry.  Spectacular battles between large groups of alligators and sharks may no longer occur, but individual crocodilians and sharks still eat each other on occasion.

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Alligator preying on a nurse shark at the Ding Darling National Wildlife Refuge near Sanibel, Florida.  This photo is on the cover of this quarter’s Southeastern Naturalist.

An article published in this quarter’s Southeastern Naturalist collects all the known incidences of alligators preying on sharks and vice versa. On Wassaw Island, Georgia a scientist saw an alligator prey upon a bonnethead shark, and he also witnessed another alligator catch and eat a lemon shark.  A case of an alligator preying on a bonnethead took place at St. Mark, Florida as well.  Bonnetheads feed on crabs in shallow water, making them vulnerable to alligator attack.  The photo above shows an alligator preying on a nurse shark. Sharks have been recorded feeding upon bottom-dwelling southern and Atlantic stingrays, and stinging barbs are occasionally found embedded in alligators.

There are no recent incidents of known shark attacks on alligators, but there are 3 records from the late 19th century, including the account mentioned in the first paragraph.  In addition to that account a shark bit an alligator in 2 near Pilot Cove, Florida in 1884, and in 1888 5 or 6 alligators battled a similar number of sharks in the Indian River, resulting in some deaths of both.

Around the world there are numerous cases of crocodiles and sharks eating each other.  Bull sharks venture into fresh water and have been recorded falling victim to Australian salt water crocodiles.  Crocodile remains have been removed from the stomachs of tiger sharks near Australia, South Africa, and Indonesia.  Caimans filled the belly of at least 1 tiger shark off the coast of South America.

Who wins a fight between an alligator or crocodile and a shark?  It depends upon the size of the individual and who bites who first.  The larger individuals have the bigger bite and the advantage, but if they are close to the same size, the first to deliver a serious bite quickly gains the upper hand.

*Note the title of the reference below.  The dispassionate scientifically proper language amuses me to no end.  Translated into layman’s English it means alligators and sharks eating each other.

Reference:

Nifong, James; and Russel Lowers

“Reciprocal Intraguild Predation between Alligator mississippiensis (American alligator) and Elasmobranchiii in Southeastern United States”

Southeastern Naturalist 3 (16) 2017

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The North Charleston Mastodon

October 8, 2017

Construction workers digging a foundation for a building in North Charleston, South Carolina 5 years ago uncovered the remains of a mastodon.  Bones including a partial tusk, femur, vertebrae, jaw, ribs, and feet were excavated.  One scientist also examined the surrounding sediment for pollen and plant remains. Apparently, the site was riverbank, and the mastodon likely was covered in flood-borne sediment.  I hope a paper is published detailing the information yielded by this site.  So far, all the information I can find comes from 2 abstracts that described poster presentations of the find at scientific meetings.  The authors didn’t even put the posters on the internet.

One presentation compared the pollen found here to that from other Pleistocene-aged sites located near the present day coast–St. Catherine’s Island, Reid’s and Bell’s Bluff, and a site along the Georgia-Florida border.  All of these sites were farther inland during Ice Ages.  Like these other sites, the North Charleston locality had a strange admixture of species presently found at higher latitudes with those still found in the region.  Water milfoil, an aquatic plant, occurred here.  This is not surprising because mastodons were semi-aquatic.  Hickory pollen was “unusually” abundant, indicating a moist temperate climate, but the pollen of red pine, a northern species, was found in association with sub-tropical Spanish moss.  Other Pleistocene sites in the region yield hemlock, basswood, and walnut–species no longer found this far south.  However, I’m skeptical about the identification of supposed red pine pollen.  This species currently occurs in New England, a region that was under glacial ice for much of the Ice Age when its range was forced south.  I doubt it occurred as far south as South Carolina though because there are no relic populations in the southeast.  Red pine pollen is distinguished from pollen of southern pines on the basis of size.  Pollen grains under 43 micrometers in size are classified as northern species of pine, while those over 43 micrometers are thought to be from southern pines.  Shortleaf pine is a common southern species of pine whose pollen grains overlap in size with red pine pollen grains.  Moreover, under the atmospheric conditions of low CO2 as occurred during Ice Ages, shortleaf pine pollen grains may have been slightly smaller than those of the present day.  In my opinion they look identical as the below photos show.  I believe pollen classified as red pine in the below reference and several other studies is from shortleaf pine which is still widespread in the region.

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Shortleaf pine pollen grains average a “maximum” 50-75 micrometers in size.

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Photos of northern species of pine pollen grains including red pine (Pinus resinosa), jack pine, and white pine.  Red pine and white pine pollen grains easily overlap in size with shortleaf pine.  Therefore, I’m not convinced of palynologists’ claim that red pine occurred in the southeast during Ice Ages.

Reference:

Rich, Fred

“The North Charleston Mastodon Site–New Insights Drawn from Paleoecological Synthesis”

The Geological Society of America: Southeastern Section–64th annual meeting

 

Inner Coastal Plain Deserts of the Ice Ages

October 4, 2017

A new study reinforces evidence, indicating some regions of southeastern North America were harsh environments during climatic phases when the ice sheets that covered Canada were expanding.  The scientists who wrote this paper took cores of sediment from 2 Carolina Bays (Jones and Singletary Lakes) located in Bladen County, North Carolina. Carolina Bays are elliptical depressions found on the Atlantic Coastal Plain that were formed during Ice Ages.  They were created by a combination of peat fires, and wind and water erosion.  The peat fires lowered the elevation, wind blew out the dried unconsolidated sediment, and wind-driven water shaped them into elliptical formations.  Jones and Singletary Lakes were also studied in the early 1950s in 1 of the first paleoecological studies of late Pleistocene environments of the south.  The new study analyzed pollen composition, charcoal abundance, and biomass; and the authors compared their results to the earlier study.  The data was dated using radio-carbon dating.

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Location of Bladen County, North Carolina.  This is the site of the study areas discussed in this blog entry.

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Photo of Singletary Lake, a Carolina Bay.  Scientists took a sediment core at the bottom of this lake and analyzed pollen, charcoal, and biomass abundance over the past 50,000 years.

Between ~60,000 years BP-~30,000 years BP climate fluctuated drastically between warm wet interstadials and cold arid stadials.  The glaciers covering Canada advanced then retreated then advanced again in fits and starts.  During glacial expansion more of earth’s atmospheric moisture became locked in glacial ice, causing prolonged droughts, but this moisture was released when glaciers were in a meltwater phase.  Oak and grass pollen increased during meltwater phases, and so did charcoal abundance.  An increase in vegetation meant there was more biomass to ignite and burn during electrical storms.  Oak and grass were fairly abundant from ~43,000 years BP-~32,000 years BP.  The environment mostly consisted of woodland and grassland during interstadials,  but about 30,000 years BP the situation deteriorated.

Ice sheets maintained a steady expansion from ~30,000 years BP-~21,000 years BP.  The initial drought that struck the region during this phase killed vegetation and caused a temporary spike of charcoal because the dead biomass was so flammable.  But after this initial spike, fire was rare to non-existent here.  Sand dunes rolled across the landscape because much of the region was sparsely vegetated.  I believe scrub oak thickets with thorny plants adapted to arid climates covered much of the landscape, but this type of environment doesn’t produce much pollen.  Thus, the amount of vegetation on the landscape then is understated in the pollen record.  For this reason I don’t believe the landscape was as bare as the authors of this study concluded when they wrote it was a “windswept sandy desert with riparian communities of pine and oak.”  Nevertheless, it was an harsh environment of thorny thickets interspersed with areas of bare soil and long distances between water and wetland environments where some trees and grass still grew.  Some tough species of mammals that could survive in this type of environment included horse, flat-headed peccary, helmeted musk-ox, and hog-nosed skunk.  Bison evolved into a smaller species more capable of living in a drier natural community. Overall, wildlife populations probably declined during this climatic phase.

About 21,000 years ago, the ice sheets began retreating and precipitation increased.  Oak and grass gradually increased in abundance, and eventually mesic species such as cypress, basswood, hemlock, and beech invaded the resulting wetter habitats.  ~12,000 years ago, man colonized the region and overhunted megafauna into extinction.  Human-set fires combined with an increase in biomass not being consumed by megaherbivores caused a great increase in fire frequency.

I’m skeptical of 1 claim made by this paper.  The authors estimated the average annual temperature and precipitation levels based on plant composition assumed from the pollen record.  During the Last Glacial Maximum they estimated the average January temperature at these sites was 20 degrees F, while the average July temperature was 68 degrees F.  However, they use 2 dubious assumptions.  They believe the pollen grains from northern species of pine can be distinguished from those of shortleaf pine, a southern species.  This is a doubtful assumption that I will examine more thoroughly in my next blog entry.  Moreover, the spruce pollen probably originated from an extinct species of temperate tree known as Critchfield’s spruce.  I don’t think they can estimate average annual temperatures based on pollen composition, unless the exact species are known with more certainty.

The outer coastal plain and the continental shelf, which was above sea level from ~80,000 years BP-~7,000 years BP, likely hosted richer environments than the inner coastal plain during stadials.  Sea breezes and weather fronts spawned in the Atlantic Ocean brought more moisture to the coast, allowing this region to maintain a mosaic of woodland, grassland, and wetland; while the inner coastal plain suffered greater aridity.  These fronts usually dissipated before they reached the inner coastal plain.  The coastal region likely served as a refuge for plants and animals that later re-colonized the inner coastal plain when climatic conditions improved.

Reference:

Spencer, Jessica; et. al.

“Late Quaternary Records of Vegetation and Fire in Southeastern North Carolina from Jones Lake and Singletary Lake”

Quaternary Science Review 174 October 2017

The Frog that ate Dinosaurs

September 28, 2017

The horned frogs of South America are often called pacman frogs because they can swallow prey as large as themselves.  Unlike all other frogs and toads, they bite and have powerful jaws attached to sturdy skulls.  Horned frogs (Ceratophys cranwelli) are probably related to an extinct frog (Beezelebufo ampinga) that lived on Madagascar during the late Cretaceous.  The anatomy between these species is similar.  Moreover, during the Cretaceous Madagascar, Africa, Antarctica, and South America were 1 continent; so a close evolutionary relationship makes sense.  Beezelebufo was much larger than extant horned frogs, reaching a weight of at least 9 pounds.  The largest living frog in the world today is the goliath frog (Conrauo goliath) of Africa, and it grows to just 7 pounds.  But Beezelebufo had a much more powerful bite.

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Beelzebufo was big enough to eat dinosaur hatchlings.

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The goliath frog is the largest living species of frog in the world.  Beelzebufo was over 20% larger.

Scientists measured the bite force of modern day horned frogs and used this to extrapolate the bite force of beezelebufo.  They estimated beezelebufo could bite as hard as a lion or tiger and harder than a wolf.  They could also bite harder than juvenile crocodilians of the same size.  Available fossil material of beezelebufo consists of individuals that were still growing at the time of deposition.  If full grown adult material is discovered and used for extrapolation, it’s possible scientists will determine adult beezelebufos had an even more powerful bite.  The authors of the below referenced paper believe beezelebufo fed upon dinosaur hatchlings and juvenile crocodilians.  Most frogs use their sticky tongues to capture prey, but horned frogs and their large extinct cousin clamp (or clamped) down with their powerful jaws.

Video of a horned frog (aka pacman frog) eating a mouse.  This species is related to the extinct beezelebufo, a frog that ate dinosaurs.

Video of bullfrog stalking and eating a sparrow.  Beezelebufo probably stalked dinosaur hatchlings at water’s edge.  Frog predation on dinosaurs continues today.  Most paleontologists believe birds descend from dinosaurs and birds are just modern day versions of dinosaurs.

Reference:

Lappin, A. Christopher; et. al.

“Bite Force in the Horned Frog (Ceratophys cranwelli) with Implications for Extinct Giant Frogs”

Scientific Reports 7 2017

 

No Need for Males

September 23, 2017

I probably read the novels At the Earth’s Core and Pellucidar about 20 times when I was between the ages of 10 and 15.  They were written by Edgar Rice Burroughs, creator of Tarzan, who also wrote a crossover novel entitled Tarzan at the Earth’s Core. The world Burroughs created fascinated me.  An old scientist, accompanied by a classic American hero, builds a drilling machine that takes them to the center of the earth where they find a land of dinosaurs, pre-historic mammals, friendly natives, and barbaric ape-like cavemen known as the Sagoths.  The novels are full of chivalrous nonsense.  After the hero, David Innes, saves a beautiful native woman from being ravaged by a Sagoth he makes a faux pas–according to the custom among the natives of this world, a saved woman was to be embraced and kissed and made a mate or freed.  Innes didn’t know he was supposed to place his hand over her head to symbolize her freedom, otherwise she was considered his slave.  It takes him a while to realize his mistake and right his wrong.  Later, he has to save her again from a race of intelligent dinosaurs that rule this world.  This race of all female dinosaurs, known as the Mahars, raise humans like livestock.  Whenever they want something to eat, they hypnotize, then eat their human chattel.

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Illustration of human being hypnotized by intelligent parthenogenetic dinosaur in Edgar Rice Burroughs’ At the Earth’s Core.  In this fantasy novel the intelligent all female dinosaurs enslaved and fed upon humans until they were routed by the hero from the earth’s surface.

In Burroughs’s novel the Mahars used science and technology to eliminate the need for males, but in the real world evolution has eliminated males in 80 species of reptiles, amphibians, and fish.  Organisms that produce viable eggs without mating are known as parthenogenetic.  Species that are all female have a couple of advantages over species that need to mate.  They can reproduce when their population is low, and energy is not wasted on individuals that produce no eggs.  Most species are not parthenogenetic because in most cases the disadvantages outweigh the advantages.  Parthenogenetic species can suffer low genetic variability leading to an increase in harmful mutations.

The New Mexican whiptail lizard (Cnemidophorus neomexicanus) is an example of an all female parthenogenetic species.  The New Mexican whiptail lizard is an hybridized cross between the little striped whiptail lizard (C. ornatus) and the western whiptail lizard (C. tigris).  The New Mexican whiptail lizard produces viable eggs that all hatch to become female clones.  New lineages are created and genetic variability is established every time a western whiptail mates with a little striped whiptail.  New Mexican whiptails engage in lesbian sex.  This, of course, doesn’t fertilize the eggs, but lesbian whiptails do produce more viable eggs, probably because the sex stimulates hormone production.

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New Mexican whiptail lizards are all female clones.

Some species of vertebrates are facultive parthenogenetic species.  They normally mate with individuals of the opposite sex, but when populations are low can produce viable eggs without mating.  Komodo dragons, boa constrictors, and some species of sharks are able to switch from sexual breeding to asexual reproduction.  The offspring can then mate normally when they come into contact with males.  Other species are considered accidental parthenogenetic species.  They produce viable eggs without mating on very rare occasions.  Parthenogenetic cases have been reported for chickens, turkeys, and pigeons.

Many species of plants and invertebrates are parthenogenetic.  Unlike vertebrate parthenogenetic species which produce all females, invertebrates and plants can produce offspring that are all female, all male, or female and male.

 

Arizona Sky Islands–Another Ecological Analogue for Pleistocene Georgia

September 18, 2017

Rapid climate oscillations, megafauna foraging, fire, and wind throws shaped the landscapes of southeastern North America during the Pleistocene.  The resulting environment in the piedmont region consisted of open oak and pine woodlands but with significant patches of closed canopy forests, savannah, prairie, scrub, and wetland.  This variety of habitats in close proximity supported a great diversity of wildlife.  The Pleistocene ecosystem in this region was unlike any extant environment.  Nevertheless, I’ve previously considered some regions as relatively close ecological analogues, resembling the Pleistocene piedmont.  Russian’s Far East was until recently a vast untracked wilderness of mixed forests with abundant game and apex predators.  (See: https://markgelbart.wordpress.com/2011/06/06/russias-far-east-the-modern-worlds-closest-ecological-match-to-pleistocene-georgia/ )  The Cross Timbers region of Texas and Oklahoma where the eastern deciduous forest gradually gives way to prairie may also be a vaguely similar analogue.  (See: https://markgelbart.wordpress.com/2012/06/13/the-cross-timbers-ecoregion-an-analogue-for-georgia-environments-during-some-stages-of-the-pleistocene/ ) I’ve come across a 3rd region that in some ways may resemble Pleistocene piedmont Georgia–the Sky Islands of Arizona, New Mexico, and northern Mexico.

Sky Islands are mountains that stand in the middle of the desert.  They host a variety of environments that change according to elevation.  A change of a few thousand feet in elevation equals the climatic difference of hundreds of miles in latitude.  In a day a man can ascend from an hot desert to temperate oak/pine woodland to boreal spruce/fir forests.  During Ice Ages the lowlands surrounding Sky Islands hosted continuous temperate forests, but now these forested environments are isolated on the mountains, surrounded by desert, hence the name Sky Island.

Mountains rise from the desert floor in Arizona, New Mexico, and northern Mexico.  They host diverse flora and fauna because the change in elevation supports a variety of environments adjacent to each other.

Sky Islands are rich in floral and faunal diversity because so many different natural communities are in such close proximity.  Sky Islands are home to 500 species of birds (over half of the species found in North America), 104 species of mammals, and 120 species of reptiles and amphibians.  Tree squirrels including Mexican fox squirrels, Arizona gray squirrels, and Mt. Graham red squirrels co-exist with rock squirrels (Spermophilus variegatus).  Rock squirrels live and nest in the ground, not trees.  13-lined ground squirrels, another species in the Spermophilus genus, also co-existed with tree squirrels in southeastern North America during the Pleistocene.  13-lined ground squirrels no longer occur in the region because they prefer open environments.  Their presence along with tree squirrels at some fossil sites suggest a more varied environment existed here during the Pleistocene.

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Rock squirrel (Spermophilus variegatus).  Sky islands are home to 7 species of squirrels.  During the Pleistocene a squirrel in the spermophilus genus also co-existed with tree squirrels in southeastern North America, suggesting a more diverse variety of habitats within the region.

Arizona Sky Islands are also famous for a small subspecies of white tailed deer known as the Coues.  For some reason the Coues deer is a popular trophy among deer hunters.  Jaguars and coati-mundi roam the Sky Islands as well.

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Coues deer–A small subspecies of white tail that lives on the Sky Islands of Arizona.

The oak savannahs and oak/pine woodlands of Sky Islands likely resemble natural communities that occurred in the piedmont region of Georgia during the Pleistocene, though they are composed of different species of trees.  Emory oak, Arizona white oak, Gambel’s oak, Canyon live oak, and blue oak grow with Arizona juniper, pinyon pine, yucca, bull grass, and bear grass.  Higher in elevation, silverleaf oak grows with ponderosa pine and Arizona pine.  Higher still, the forest may consist of ponderosa pine, Englemann Spruce, and Douglas Fir–trees of the northern Rocky Mountains.

Acorn Woodpecker Photo

Acorn woodpeckers are a communal species that hoards acorns.  They are a common species on Sky Islands.

The different types of forest attract many different species of birds.  Birds that prefer coniferous forests can be found with those that like oak forests. Tropical species including trogons, thick-billed parrots, buff-colored nightjars, and Arizona woodpeckers inhabit Sky Islands.  These species are found at few other sites north of the Rio Grande River.

 

New Species of Late Pleistocene Ground Sloth and Peccary Discovered on Yucatan Peninsula

September 13, 2017

My ongoing mission to catalogue the faunal composition of piedmont Georgia as it was during the late Pleistocene is but an educated guess.  I base my guess on the lone fossil site in the region plus fossil sites located to the north, south, and west of the piedmont.  (See for my list: https://markgelbart.wordpress.com/2013/12/27/if-i-could-live-during-the-pleistocene-part-xii-my-mammal-checklist/ ) I think I know most of the mammal species that occurred here during the Pleistocene, but there were probably species living in the region I never would have guessed.  Even in regions with many Pleistocene-aged fossil sites, scientists are still discovering the presence of new species.  Within the last 5 years paleontologists identified giant short-faced bear (Arctodus simus) and collared peccary (Tayassu tajacu) specimens in Florida where these species were not formerly known.  The dhole (Cuon alpinus) crossed the Bering land bridge sometime during the Pleistocene, yet the only fossil specimens of this species in North America were found at 1 site in Mexico.  This means all the dholes that lived between Alaska and Mexico left zero fossil evidence, or at least none that has been found to date.  And now, just within the last 2 years, scientists have identified 2 new species of large mammals that lived on the Yucatan peninsula during the late Pleistocene.

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Map of the Quintana Roo province on the Yucatan Peninsula.  Evidence excavated from sinkhole caves indicates an unique fauna resided here during the late Pleistocene.

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Skull of Xibalbaonyx oviceps found in Yucatan sinkhole.

The Yucatan peninsula is dotted with numerous sinkholes and caves because rain water unevenly dissolves underlying limestone bedrock.  The sinkholes and caves preserve remains of animals for tens of thousands of years.  Cave divers have discovered the bones of gompotheres, glyptodonts, ground sloths, llamas, horses, tapirs, peccaries, spectacled bears, saber-tooths, bobcats, rabbits, fruit bats, and humans in these subterranean spaces.  (I’m aware of 4 mostly complete human skeletons found in Yucatan sinkholes and caves–1 dating to the incredibly early date of 14,350 calendar years BP.)  Bones of Shasta ground sloths and collared peccaries are among the specimens recovered here, but relatives of each, previously unknown to science, have recently been described in the scientific literature.  The new ground sloth species was identified from a specimen found in the Zapote sinkhole.  It was a mostly complete skeleton of a sub-adult that weighed at least 500 pounds when it was alive.  It is thought to have been adapted to a desert grassland environment.  Scientists gave it the unpronounceable scientific name–Xibalbaonyx oviceps.  It was closely related to Jefferson’s ground sloth (Megalonyx jeffersonii), a species that occurred all across North America from Florida to Alaska.  Perhaps X. oviceps was a desert offshoot of Jefferson’s ground sloth.  The new species of peccary was given the more pronounceable scientific name of Mucknalia minimas. I haven’t been able to obtain a copy of either paper describing the new species.  When I do I may write an addendum to this blog entry.

The presence of 2 species seemingly endemic to the Yucatan peninsula indicates the region was ecologically unique.  The area around the Hoyo del Negro fossil site (See: https://markgelbart.wordpress.com/2015/08/08/the-hoyo-negro-fossil-site-in-yucatan-mexico/ ) was a mix of tropical forest, thorny scrub, and wetland; but further inland desert grassland predominated.  I think small sinkhole lakes, like oases, probably existed in drier areas.

Who knows?  Maybe the piedmont region of southeastern North America hosted endemic large mammal species during the Pleistocene that are currently unknown to science.  Unfortunately, the lack of sites suitable for fossil preservation in the region could keep them cloaked in mystery for eternity.

On an unrelated note: While researching this blog entry, I learned about a llama specimen (the extinct  Hemiauchenia macrocephela) found in a Yucatan cave that was apparently butchered, cooked, and eaten by humans.  This information doesn’t seem to be generally known in the archaeological literature.

References:

Gonzalez, Arturo: et. al.

“The Arrival of Humans on the Yucatan Peninsula. Evidence from Submerged Caves in the State of Quintana Roo, Mexico”

Current Research in the Pleistocene January 2008

Stinnesbeck, S.; et. al.

“A New Fossil Peccary from the Pleistocene-Holocene Boundary of the Eastern Yucatan Peninsula, Mexico”

Journal of South American Earth Science 2016

Stinnesbeck, S. et. al.

“Xibalbaonyx oviceps, a New Megalonychid Ground Sloth (Folivora: Xenarthan) from the Late Pleistocene of the Yucatan Peninsula, Mexico and its Paleogeographic Significance”

Palz 91 June 2017

 

How Far South did the Wolverine (Gulo gulo) Range during Ice Ages?

September 7, 2017

The voracious wolverine preys upon deer, caribou, and even moose when these much larger mammals flounder in deep snow.  The padded paws of the wolverine allow them to stay on top of the snow while the heavy hooved deer sink, making it easy for the wolverine to lock their jaws on a throat. The wolverine also preys on smaller animals and will eat insects and berries.  They live in remote wilderness areas, preferring high elevations with deep snow and plenty of tree or shrub cover.   Wolverines benefit from the presence of other large predators because they are just as much scavenger as predator.  During summer and fall wolverines are too clumsy to actively chase deer but will drive off much larger predators from their kills.  After they consume as much as they can eat, they spray musk on the remains, and it become unpalatable for other carnivores.  Wolverines store caches of dead meat during winter and are ideally suited to survive in cold unproductive natural communities.

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Historical range of the wolverine.  Camera traps suggest they have recently recolonized northern California. They also live in Eurasia.  During Ice Ages, wolverines probably ranged along the southern Appalachians perhaps as far south as north Georgia and Alabama.

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Male wolverines reach weights of 60 lbs but can drive away bears, cougars, and wolf packs. Wolverine cubs sometimes fall victim to the latter 2.

Wolverines occupy very large territories.  Males in Montana patrol 162 square miles on average, while male Yellowstone wolverines average a territory of an astounding 307 square miles.  Wolverines  live in low densities in boreal forests, and this makes their remains rare in the fossil record.  Nevertheless, subfossil remains of wolverines, dating to the Pleistocene, have been excavated from Maryland, Pennsylvania, Wyoming, Colorado, Nevada, Romania, Italy, Germany, France, and the United Kingdom.  (The wolverine is an Holarctic animal, living on both sides of the Arctic Circle.)  The specimen from Cumberland, Cave, Maryland is the southernmost known record of the wolverine in eastern North America and this is south of their known historical range during colonial times.  I hypothesize wolverines ranged into the southern Appalachians as far south as north Alabama and north Georgia during Ice Ages.  The key is deep snow–any climatic phase when deep snow regularly occurred at high elevations in the southern Appalachians would have been an invitation for wolverine range expansion south.  Other boreal species of mammals are found in the fossil record this far south including caribou, fisher, pine marten, porcupine, bog lemming, and red-backed vole.  Wolverine skeletal evidence is probably absent because they lived in low population densities at high elevations in forested environments where fossil preservation is rare.  Historical wolverine range is closely correlated with regions where snow stays on the ground through a good portion of spring.  Undoubtedly, spring snow cover existed in the southern Appalachians during the coldest stages of Ice Ages.

Most of the wolverine’s present day range was covered by glacial ice during Ice Ages, so it seems likely their range shifted south, like that of so many other species then.  How far south did this range shift?  We can only speculate.  But this is an animal that requires deep wilderness, and North America was nothing but deep wilderness before man.  Wolverines won’t cross clear-cuts or burned over land.  The main factor restricting wolverine range before man were the extensive grasslands that likely formed an ecological barrier to their expansion below the southern Appalachians.

References:

Hornocker, M; and H. Hash

“Ecology of the Wolverine in Northwestern Montana”

Canadian Journal of Zoology 59 (7) 1981

Inman, R.

“Wolverine Ecology and Conservation in the Western U.S.”

Swedish University Doctoral Thesis 2013

http://www.paleobiologydatabase.com

 

 

Disjunct Populations of Western Insects Occur on Black Belt Prairies of Southeastern North America

September 4, 2017

The Black Belt Prairie region extends through Alabama and Mississippi with additional isolated patches in Georgia and Tennessee.  There is a different Black Prairie region in east Texas.  The chalky soils of Black Prairies favor grass over trees, and in the southeast they produce a mosaic of forest and prairie.  Western species of plants such as little bluestem grass grow on Black Prairie landscapes, and they attract species of insects not normally found in southeastern North America.  At least 15 species of insects that occur on western grasslands exist as disjunct populations on the Black Prairies located in southeastern North America.  This includes the white bee (Tetralonella albata)–a pollinator of prairie clover–as well as 4 species of long-horned beetles and 10 species of moths.  The red-femured long-horned beetle (Tetraodes femorataand the Texas long-horned beetle (T. texanus) feed upon milkweed.  Most of the moths are hosts on flowers in the aster family.

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Map of Black Belt prairie region in southeastern North America.  (Shaded orange.)  Although the map doesn’t show it, some isolated pockets of Black prairie occur in Georgia as well.

Bee on Dalea - Tetraloniella albata

The white bee occurs in disjunct populations in Mississippi and Arkansas.  The main population occurs from Colorado and Illinois to California.

Milkweed Longhorn Beetle (Tetraopes sp.) - Tetraopes femoratus

The red-femured long-horned beetle ranges from the Great Basin to Mexico.  Disjunct populations occur in the Blackland Prairie Region.

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Epiblema iowana–another western species found in the Black Belt prairie region plus 1 site in Florida.

A grassland corridor formerly must have connected the Great Plains grasslands with the Black Belt prairies of the southeast.  Some scientists speculate that before the last Ice Age this corridor may have existed along the Grand Prairie of Arkansas or through the Arkansas River Valley.  The Mississippi River was lower then and interspersed with lightly vegetated sandbars that allowed for insect passage between the 2 regions.  After the last Ice Age glacial meltwater expanded the Mississippi River, blocking insect passage, but a grassland corridor between the Great Plains and the southern Black Belt Prairie may have existed through cedar glades in Tennessee to Kentucky to Illinois where the Mississippi River was more narrow. Currently, the Mississippi River and forested habitat separate the 2 grassy regions.

During Ice Ages the Black Belt prairies may have served as a refuge for many species of grassland insects found in the Great Plains today.  Forests of jack pine and spruce replaced Great Plains grasslands during glacial phases.  Summers were cooler and shorter.  Species of insects that preferred grassland communities and long warm summers retreated to the Black Belt prairies and Gulf Coast grasslands of southeastern North America.  Populations considered disjunct today may actually be seed populations that replenish Great Plains insect fauna following the end of Ice Ages.

Reference:

Peacock, Evan; and Timothy Schauwecker

“Blackland Prairies of the Gulf Coastal Plain”

University of Alabama Press 2003

 

Pleistocene Saiga Antelopes

August 31, 2017

The saiga antelope (Saiga tatarica) ranged from western Europe to Alaska and the Yukon during some climate phases of the late Pleistocene.  This range closely corresponds with an environment known as the mammoth steppe.  This paleoenvironment was similar to the present day central Asian steppe but was more productive, hosting a greater variety of plants and microhabitats that included scrub, woodland, and wetland embedded in a sea of grass.  Summers were cool, winters were long, wind was constant, and precipitation was infrequent.  The bulbous nose of the saiga antelope is an adaptation for living in this kind of environment.  It helps warm frigid air and filter the dust in a dry windy climate.  The range of the saiga antelope has been greatly reduced since the late Pleistocene due to changes in the environment and overhunting by man.  Nevertheless, saiga antelope occurred in eastern Europe as late as the 17th century, indicating they are not a relict species confined to steppe grasslands.  A recent scientific study examining the bone chemistry of subfossil and extant saiga antelope specimens concluded this species can survive on a greater variety of plant foods than present day populations consume.

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Saiga antelopes are critically endangered today but lived from the British Isles to the Yukon, Canada during the late Pleistocene.

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Present day saiga antelope range.  During the Pleistocene they occurred from western Europe to Alaska.

This study found the diet of the saiga antelope overlapped with that of the caribou (Rangifer sp.) in southwestern Europe between 20,000 years BP-15,000 years BP.  It seems likely both species were subsisting upon lichen during winters when other plant foods were scarce.  Pleistocene saiga antelope apparently had a greater flexibility in their diet than present day populations.  The authors of this study suggest saiga antelope could potentially be introduced outside their present day range.  Poaching and disease outbreaks are endangering the surviving remnants of saiga antelope populations, so it could prove beneficial to establish new populations outside their present day range.  However, it’s possible some Pleistocene populations of saiga antelope may have been a distinct now extinct species with different dietary tolerances.  Some Russian paleontologist noted some morphological differences in saiga antelope specimens found outside their present day range, and they proposed a new species–Saiga borealis. Other paleontologists don’t accept this designation.  So far, no genetic studies have solved this difference of opinion.

The saiga antelope is considered a distant sister clade to the springbok-gerenuk clade.  They are the sole survivors of antelopes that roamed Europe before Ice Ages began to occur.  None of their closest relatives were able to evolve fast enough to survive deteriorating climatic conditions.

Reference:

Jurgensen, J.; at. al.

“Diet and Habitat of the Saiga Antelope during the Late Quaternary Using Stable Carbon and Nitrogene Isotope Ratios”

Quaternary Science Review March 2017