Pleistocene Rattlesnakes

Too many people have an irrational fear of snakes.  One of my neighbors was once frightened by an harmless garter snake a car had flattened like a tortilla in front of her house.  I have peeved more than 1 neighbor over the years by defending a rattlesnake’s right to life.  In my opinion rattlesnakes are an interesting member of the local fauna; less dangerous than big dogs, speeding cars, and lightning.  The odds of getting bitten by a rattlesnake are exceedingly small.  Rattlesnakes do not exist to bite people.  Instead, they want to eat small animals, mate, and stay warm.  They want larger animals, such as humans, to leave them alone.  The majority of snake bite victims stupidly handled the serpent and would have never been bitten, if they would have left it alone.  There is no reason to fear snakes, but they should be respected and not treated like a pet or a toy or as proof of faith in God.

Rattlesnakes are not considered endangered, but they were formerly more common prior to human settlement.  The first white men to explore Kentucky were constantly blundering into them. ( See: https://markgelbart.wordpress.com/2012/04/20/excerpts-from-the-journal-of-an-expedition-to-kentucky-in-1750/ ) Habitat loss and direct destruction during rattlesnake roundups greatly reduced their population.

Genetic evidence suggests the rattlesnakes first diverged from other pit vipers about 22 million years ago.  This divergence probably occurred in western North America because there are more species in that region than anywhere else.  There are 30 species of rattlesnakes, and all of them live in America.  Traditionally, herpetologists categorized 27 species in the crotalus genus and 3 in the sistrurus genus, but the most recent genetic analysis suggests 1 of the sistrurus species should be considered a crotalus.

There are 3 species of rattlesnakes that range throughout southeastern North America today–the eastern timber (Crotalus horridus), the eastern diamondback (C. adamanteus), and the pygmy (Sistrurus miliarus).  Evidence from the fossil record shows all 3 of these species have lived in the region since at least the late Pliocene over 2 million years ago.  However, the eastern timber rattlesnake is presently absent from peninsular Florida, but it did live there during the mid-Pleistocene.  This species probably became extirpated from the peninsula of Florida during a time of high sea levels when  most of the state was  inundated by ocean, and for some undetermined reason it has failed to recolonize its former territory.  I think its ecological niche is now occupied by the other 2 species of rattlers which are better adapted to flat land habitat.  Eastern timber rattlers prefer rocky deciduous woods where they can seek thermal refuge under crevices between boulders and the ground, while pygmies and diamondbacks seek out gopher tortoise and rodent burrows.

Eastern timber rattlers (and copperheads?) in an hibernaculum.

Eastern timber rattlesnake range map.  During the mid-Pleistocene they lived in peninsular Florida but have failed to recolonize this region following interglacial sea level rise.

The Eastern diamondback rattlesnake is the largest species of crotalus.

Eastern diamondback range map.

Pygmy rattlesnakes reach a length of only 2 feet long.

Pygmy rattlesnake range map.

There are many species of interesting western rattlesnakes including the prairie, sidewinder, Mojave, and Mexican small-headed.  The genes of the latter species (C. intermedius) reveal a past history of alternating isolation and reunion between populations.  Currently, populations of Mexican small-headed rattlesnakes and closely related species are isolated from each other by desert.  They inhabit pine/oak montane forests at high elevations.  But during Ice Ages the pine/oak forests expand into the desert and populations isolated during interglacials reconnect.

The composition of rattlesnake venom varies regionally and evolves over time in response to environmental changes and evolving defense adaptations among prey species.  An environment that changes from one with an abundance of prey to one of scarcity may lead to rattlesnakes with more potent venom.  Rattlesnake venom has a slew of toxins that can damage nerves, muscles, and blood.  This makes it difficult to manufacture anti-venom that will work.

References:

Bryson, Robert

“Ephemeral Pleistocene Woodlands Connect the Dots for Highland Rattlesnakes of the Crotalus intermedius Group”

Journal of Biogeography 2011

Murphy, Robert et. al.

“Phylogeny of the Rattlesnakes (Crotalus and Sistrurus) Inferred from Sequences of Fine Mitochondrial DNA Genes”

Biology of the Vipers 2002

 

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After the Apocalypse: My House at 20, 100, and 10,000 Year Intervals

Alan Weisman’s book, The World Without Us, in part inspired my blog.  In his book he imagines a world where humans suddenly become extinct, and he speculates about the resulting ecological changes and how anthropogenic structures would decay.  I am particularly interested in landscapes devoid of human influence.  I chose to devote my blog to the paleoecology of southeastern North America as it was before people lived here, rather than after people become extinct.  But for this blog entry, I am going to speculate about what changes would occur to my lot and my immediate neighborhood, if a plague suddenly wiped out 100% of worldwide humanity.

Without anyone around to maintain it, my house would become covered in grape vines, Virginia creeper, and pine straw in 3 years.  After 100 years the only thing left standing would be the chimney.  Sand, held down by pioneer plants, would cover the road completely.

During the growing season, I have to  constantly cut back the Virginia creeper that otherwise would completely cover my house.

My peach trees would probably die in less than 20 years, but my blueberry bushes, persimmon and mulberry trees, and chives would likely still be alive after 20 years.

My patch of sunchokes would last decades…until trees shaded them too much.

My House 20 Years After the Extinction of Homo sapiens

I rake the pine straw off my roof twice a year and cut back Virginia creeper and grape vines twice a month during the growing season.  Without me all 3 completely covered my house in 3 years.  This hastened wood rot.  A sagging area of my roof caved in and several generations of squirrels have lived in the attic.  The house is still standing, though the roof leaks in numerous places and the inside smells like mildew.  An oak tree in the front yard is now quite large and some of its branches cover my daughter’s Toyota Corolla.  The tires on both Toyotas are flat, and the metal bodies are rusting.  A hailstorm cracked windows, and some are shattered.  Mosquitoes breed in puddles on the floorboard of 1 of them.

The peach trees in my scrub-covered backyard have died, but the mulberry, a native tree, is thriving and forms a closed canopy on the side of the yard with a black cherry and oak.  Both native fruit trees provide plenty of summer food for songbirds.  Much of the backyard is near impassable thicket and home to a happy family of rabbits.  The lot across the street from mine is also a thicket of pine and oak saplings and persimmon, most of it covered in vines.  Before people became extinct, a street sweeper kept sand from covering the road in front of my house.  But now most of the road is covered in sand, leaves, pine straw, and other organic debris; and pioneering grasses and flowers are taking root in many places.  The road is the only passable track in the vicinity and serves as an animal trail.  Scat of all kinds is visible.

Human hunters and automobiles caused a 30% annual mortality rate in the deer population.  But after humans became extinct the deer population skyrocketed, and it is still high 20 years later.  Herds of 200 occasionally form, and they browse down much  of the vegetation but here in the south with a long growing season, they never starve.  Instead, predator populations increased and partially keep the deer population in check.  Both coyotes and bobcats take a toll, especially on spring fawns.  Wild hogs have expanded out of nearby Phinizy Swamp and are regular travelers along the road.  They eat pine sapling roots and acorns but don’t seem to be having a big impact on the dense young forests popping up everywhere.  Rabbits like the yards that have become covered in scrub habitat.  Feral cats hunt them.  They are still abundant but suffer shorter lifespans without people feeding them.  Packs of feral dogs are uncommon because coyotes outcompete them.  Cougars and bears are increasing elsewhere but have not yet colonized the vicinity.

Without humans cats would be just as abundant as they are now, but they would have shorter lifespans.

My Lot 100 Years After the Extinction of Homo sapiens

The chimney is the only structure still standing from my old house.  Most of the houses on this street look like collapsed ruins.  Some power line poles have rotted and tipped over, and during several ice storms trees smashed through power lines.  About half the poles still stand but the wire is all on the ground covered in dense vegetation.  The ground around my former home is littered with bricks, most covered with dirt, grass, leaves, and pine straw.  A sapling is growing through a crack in the cement slab that my house formerly rested upon.  The rusty washing machine and dryer are covered in brambles.  There is a squirrel’s nest on top of the refrigerator.  A rotting pine log and all sorts of organic crud camouflage what used to be a queen-sized bed. The fabric rotted away, but the springs and metal parts can still be seen. An oak is growing through 1 of the rusted hulks that used to be a car.  My backyard is a thick forest.  However, the lot across the street is more of an open woodland.  Perhaps a fire burned through that side of the road.  The road is not recognizable–scrub vegetation broke through cracks in the pavement which is now only visible in a few eroded places.  However, an animal trail still winds around in the general direction of where the road used to be.

Deer and wild hog are still abundant and are preyed upon by coyotes and bobcats here, but a cougar includes my lot as part of his territory.  Bears occasionally pass through too, looking for turkey eggs, for there is a big flock roosting in the vast local woods.

My Lot 10,000 Years After the Extinction of Homo sapiens

There is no trace of my house, at least on the surface.  Bricks, metal, and plastic are buried under several feet of sediment.  The surrounding landscape is an open woodland consisting of loblolly pine and sand laurel oak–the species that have long co-dominated this belt of fall line sand hills.  The trunks on many of the oaks are 6 feet thick, but the poor soil keeps them from growing very tall.  Fire and megafauna foraging maintain a grassy understory between the widely spaced trees.  The climate is beginning to gradually sink into an Ice Age, but the change is imperceptible to the great herds of horses, long-horned cattle, bison, wild boar, and deer that live in the vicinity.  Jaguars long ago joined the cougars and wolves in hunting the hooved animals.  The wolves descend from coyote x dog hybrids.  They evolved to a larger size that helps them bring down larger prey.  Bears are abundant, but feral cats, along with other small predators such as raccoon, fox, and opossum are less common than they were in anthropogenic environments because the larger predators keep their populations in check.  It’s almost like the Pleistocene again.

 

Possible New Megafauna Kill Site Found in Mexico

Whenever news organization report new paleontological discoveries, I can always count on the journalist to sensationalize the find, and they often make assumptions that are factually incorrect.  Here is an example.  A mostly complete Columbian mammoth (Mammuthus colombi) was unearthed in Tultepec, Mexico in December 2015 when workers digging a trench for a new sewer line found the bones 6 feet below the surface of the ground.  Luis Cordoba Barradas, a Mexican archaeologist, took over the excavation.

Location of Tultepec, Mexico where the remains of 1 mammoth were found 6 feet underground.  It may have been butchered by humans.

Mammoth skull with intact tusks in the process of being excavated in Tultepec.

Over a dozen news services reported the discovery, but important information is missing from all the reports.  This particular mammoth lived some time between 14,000 BP-12,000 BP and was 20-25 years old at the time of its death.  According to all the reports, the position of the bones suggests possible human butchery.  But this is a sensationalist overreach because many of these reports left out the alternative explanation–the position of the bones could be attributed to human butchers OR natural predators scattering the bones.  None of the new reports go into the details of why this might be considered a human-killed specimen.  Were stone tools found associated with the bones?  Are butcher marks on the bones?  Did they find animal gnaw marks?

A detailed description of the specimen hasn’t been published in the scientific literature yet, as far as I know.  The area was a lake during the late Pleistocene, and the mammoth may have been stuck in the mud when it was killed.  I would be interested in the stratigraphic context, but I’ll probably have to wait until the important details are published in a journal.  (I did send the archaeologist an email, asking him for more details.  I’ll post his response, if he sends me one.)

The news reports reveal the confusion of the original reporter.  More than 1 report mentions that this specimen was a subspecies of mammoth.  Obviously, many of the articles were simply copied verbatim from information reported in someone’s original report. (In other words…plagiarized)  I think this journalist was under the mistaken impression that the Columbian mammoth was a subspecies of the woolly mammoth (Mammuthus primigenius).  This is incorrect.  The Columbian mammoth was a distinct species, though recent genetic evidence, along with old anatomical studies, show the 2 species interbred where their ranges overlapped.  (See: https://markgelbart.wordpress.com/2016/02/18/the-southern-and-northern-range-limits-of-the-columbian-mammoth-mammuthus-colombi/ )

Hopefully, a scientific journal will publish a paper about this species because the news reports are just so inadequate.

Pleistocene Fossils and Nazi Soldiers Buried in Latvia

About 30 years ago I took a business class at Augusta College that revealed 1 of my most disappointing shortcomings.  The professor separated us into groups of 7, and we were assigned topics for discussion everyday.  After several weeks of discussions the professor told us to rank group members in order of most to least influential.  I ranked myself 3rd and felt it was a fair assessment.  But I ranked 6th in the overall average of everybody’s rankings.  Much to my astonishment, I was ranked well behind a guy (that I ranked last) who often showed up to class tripping on acid and had not spoken 1 word during the entire assignment.  It was then when I first realized I had no influence, and I felt so depressed I almost cried.  It explained why I had such a hard time getting women to go on dates with me.  It explained why ridiculous jerks who continuously misused and abused women could get any dates they desired, while I was lucky to get a condescending rejection, if the woman even acknowledged my attention at all.

Now that I am older, I’ve learned to accept the reality that I have little influence or charisma.  I am “low key” as 1 of my former supervisors reported in a complimentary job evaluation.  I even take solace in the knowledge that some of the most influential people in history are considered monsters.  I’ve recently been re-reading The Rise and Fall of the Third Reich by William Shirer–the best history book I’ve ever read. The details of how Hitler completely took over a country amaze me.   Adolf Hitler was clinically insane.  A psychiatrist diagnosed him with manic-depressive psychosis, now known as bipolar disorder.  (The Nazis eventually killed the doctor and made it look like a suicide.)  Yet, he was easily the most influential man of the 20th century.  He drastically changed the course of history after becoming the dictator of Germany with the legal power of life and death over every citizen there and in all the territories conquered under his rule.  He even replaced the customary salutation of “hello” and “goodbye” with “Heil Hitler.”  He is responsible for the deaths and misery of millions of people.  So if anybody ever criticizes me for having no influence or lacking charisma, I can always tell them, “well, you know who DID have a lot of influence?…Adolf Hitler.”

I’m a nice guy, but I have no influence.  Hitler…not a nice guy…was the single most influential man to live during the 20th century.  I used to feel sad about my lack of charisma, but when I think about this, I don’t feel as bad.

My late father survived the holocaust in Buzcazc, Poland.   One day, the Nazis ordered all the adult Jewish men to the town soccer stadium.  My grandfather decided not to obey that order, although he considered it.  That night, my father’s family heard shots from the direction of the soccer field and a few minutes later, an athletic man who ran and escaped, told them the Germans lined up and shot all the Jewish men in attendance.  Shortly after this incident, my grandfather paid a Ukrainian farmer to hide his family in an hayloft.  There, 6 people lived on a very low calorie diet for 2 years before they were liberated by the Russian army.  However, all of my father’s grandparents, uncles, aunts, and cousins were killed in concentration camps or shot upon initial confrontation.  My father always liked to watch WWII movies because they depicted the killing of Nazis.  Until his death, he never tired of watching “killing Nazis”–his term for his favorite war movies.  My dad would have enjoyed a movie about the Russian military campaign in Latvia during 1944 that occurred to the north of where he was liberated, but Hollywood has yet to depict this battle.  The Russians trapped 350,000 German soldiers here.  They killed 100,000 and captured the rest.  All of the bodies were buried near where they were killed, and the blue clay soil helps preserve the Nazi skeletons and artifacts that litter the subsurface of the Latvian countryside.

Location of Latvia.  The Russian army trapped 350,000 German soldiers here.  100,000 were killed and buried on the battlefields.  In many rural areas live humans are outnumbered by buried German corpses.

Rural Latvia is an economically depressed region and most of the people who lived there moved to the city or to other European countries.  So in many places, Nazi corpses outnumber live people.  The old poor alcoholics who remain often dig up Nazi graves and sell the artifacts for cash.  German army dog tags sell for $60.  SS dog tags sell for several hundred dollars.  An helmet can fetch $90.  The market for Nazi artifacts is strong and can be lucrative.  According to Bloomberg Businessweek,  “Herman Goering’s sweat-stained uniform” sold for $126,000.  An orthodox Jew bought Josef Mengele’s diary for $245,000.

The same properties in Latvian soil that have preserved Nazi skeletons also saved paleoecological evidence dating to the Pleistocene.  Stratigraphic cores reveal evidence of past fluctuations in climate alternating between temperate, cold, and full glacial.  Pollen analysis shows a forest of elm, basswood, and hazelnut predominated during warm interglacials.  Immediately before and after glacial maximums the environment consisted of grassy steppe with pockets of birch, alder, spruce, and pine.  Glaciers have entirely covered Latvia during the glacial maximums of the numerous Ice Ages that occurred over the past 2-3 million years.  Over 40 specimens of mammoths have been excavated in Latvia (impressive for such a small little studied area), and caribou remains are common as well.  A Latvian can dig in their backyard and find Nazi skeletons, and if they keep digging deeper, they might find the remains of a mammoth too.

References:

Rogers, Thomas

“The Bodies”

Bloomberg Businessweek   September 4, 2016

Zeles, Vital; Maris Nartiss, and Tomas Satir

“Pleistocene Glaciation in Latvia”

In   Quaternary Glaciation–Extent and Chronology: a closer look

Edited by J. Ehles, P.L. Gillard and P.D. Hughes

The Mysterious Decline of the Eastern Spotted Skunk (Spilogale putorius)

I was delivering newspapers on Sand Bar Ferry Road in Augusta, Georgia on the only occasion I’ve ever seen a live spotted skunk.  In the 26 years since that 4 am encounter, I’ve driven by maybe 2 road-killed specimens on I-20 between Augusta and Atlanta.  The eastern spotted skunk is a rare animal, though it has a wide range from southern Canada to Florida and west to the prairie states.  But it has not always been as uncommon as it is today.  Like other small carnivore/omnivore species such as opossum, raccoon, and fox; it adapted well to European modification of the wilderness.  They benefitted from the elimination of larger predators, and the creation of edge habitat between forest and farmland.  Formerly, spotted skunks could often be found in burrows under barns and hay stacks where they hunted their favorite prey–mice.  Until the 1940s trappers killed over 100,000 annually in some states.  However, within a 3-5 year period spotted skunk populations declined by 90% and have never recovered.  Scientists don’t know why.

Spotted skunk doing a handstand.  If you see one doing this, flee the area…it’s about to spray.

Scientists suspect many causes in the spotted skunk population decline but none fit the timing or align with the known facts.  Modernization of farming techniques is 1 suspected cause.  Modern farmers expand cultivated fields and eliminate natural border areas, and they consolidate barns.  This does infringe on spotted skunk habitat.  However, agricultural modernization has been a long term process, and the decline of the spotted skunk occurred rapidly.  Pesticide use is another suspect because insects are an important item in the spotted skunk’s diet.  But widespread use of pesticides began after the decline of spotted skunk populations.  Scientists looking at the data can’t “fully implicate” over trapping as the culprit in the decline.  They also can’t find a definite correlation with any diseases.  Most small animals respond cyclically to disease outbreaks, but eventually inherited immunity among some individuals allows their numbers to bounce back.  Spotted skunk numbers never recovered from their sudden decline.  The mink enteritis virus spread throughout mink farms in the 1940s, so this is 1 possible disease that may have devastated spotted skunk populations.  Still, they should have recovered by now.

I propose diseases spread by feral or domestic cats may play a role in keeping spotted skunk populations depressed.  Skunks and house cats are known to interact in a friendly manner.  They even play together, and skunks will often feed on the food left outside for cats.  Because cats are so numerous, they are more likely to have stronger immune systems and can survive diseases that the far less common skunks are susceptible to.

Video of a cat playing with 2 wild baby skunks.  House cats and skunks get along well together.  I hypothesize diseases carried by cats depress skunk numbers.

The spotted skunk is listed as a species of conservation concern.  Unfortunately, it receives little attention because it is…just a skunk.  This is a shame.  The spotted skunk is a neat little mammal, usually weighing less than 3 pounds.  It is more acrobatic than its larger, more common cousin, the striped skunk (Mephitis mephitis).  It can climb trees and when it is threatened it stands on its front paws and can accurately spray from 10 feet away.  This species is little studied.  One of the few studies of spotted skunks (in the Oachita Mountain National Forest, Arkansas) determined they prefer closed canopy forests with dense undergrowth.  The dense undergrowth keeps them hidden from their most dangerous predator–the great horned owl.  Ironically, the habitat they prefer is the opposite of what wildlife managers are aiming for here.  Wildlife managers are using prescribed fire to create open short leaf pine forests with grassy understories where spotted skunks would be vulnerable to predation.

The spotted skunk has a long evolutionary history in North America.  It likely descended from a late Pliocene ancestor known as Spilogale rexroadi over 2 million years ago.  Fossil remains of Spilogale putorius dating to the Pleistocene have been excavated all over North America including a specimen recovered from Ladds Mountain in north Georgia.  I hope this species can survive in the future from the scourge of the cat diseases or whatever problem(s) ails it.

References:

Gompper, Matthew; K. Hackett

“The Long Term, Range-Wide Decline of a Once Common Carnivore: the Eastern Spotted Skunk (Spilogale putorius)”

Animal Conservation May 2005

Lesmeister, Damon: Matthew Gompper, Joshua Millspagh

“Summer Resting and Den Site Selection by Eastern Spotted Skunks (Spilogale putorius) in Arkansas”

Journal of Mammalogy 2008

 

The Ecology and Evolution of Live Oaks (Quercus subsection virentes sp.)

The southern live oak (Quercus virginiana) is my favorite species of tree.  I love the sprawling canopy, usually covered in silvery-gray Spanish moss, and the way they grow in shady groves that cool off their native habitat–the hot sea islands and lowlands of southeastern North America.  The southern live oak is specially adapted to grow on the edge of maritime forests where their sturdy limbs can reach over adjacent fresh or saltwater marshes.  Before Europeans modified the environment, most live oaks occurred on the edges of watery habitats.  Unless a natural gap occurred within the forest, the limbs of most individual trees sprawled in one direction over water, enabling them to capture sunlight that other species of trees couldn’t reach.  But man cleared the original maritime forests and replanted live oaks in groves where the limbs of widely spaced trees could sprawl in all directions.  The limbs evolved to withstand strong sea winds, and when Europeans first colonized the region they were quick to make use of the solid wood for ship-building.  Today, the tree is planted as an ornamental, and its abundant acorn production feeds wild hog, deer, squirrel, and other wildlife.

There are 7 species of live oaks including the southern, the sand (Q. geminata), the dwarf or runner (Q. minima), the Cuban (Q. sagraeana), the Texas (Q. fusiformis), the Baja (Q. bradegeei), and the encina or Central American (Q. oleoides).  All of these species grow at low elevations in well drained soils.  They are evergreen trees that require cross pollination.  Live oaks will occasionally hybridize with other species of white oaks and with other species of live oaks in ranges where they overlap.  The genetic evidence suggests white oaks first evolved 28 million years ago, and the live oak group (a subsection within the white oak family) diverged from other white oaks 11 million years ago.

The Seven Sisters live oak in Mandeville, Louisiana is the largest and oldest known live oak in the world. It is estimated to be 1500 years old.

Sand Live Oak (Quercus geminata) in a stand of open pine savannah.  It is more fire tolerant than Quercus virginiana.

Dwarf live oak (Q. minima).  This species is fire dependent.  Its root system is much larger than the shrub itself.

The ranges of southern, sand, and dwarf live oak overlap; but they don’t hybridize often because they flower at different times and they prefer different habitats.  The southern live oak is a large tree that is fire intolerant.  This species can only grow successfully in environments where it is protected from fire such as islands surrounded by salt marsh and inlets or hardwood hammocks surrounded by swamp.  The sand live oak is fire tolerant, and it can grow in pine savannahs subject to frequent fire.  The runner live oak is a small shrub that is fire dependent.  It has an extensive root system underground and will re-sprout after a ground fire, but it can’t grow in shade.

Scientists believe live oaks evolved in southern North America because most species are frost tolerant.  The encina or Central American live oak lost this frost tolerance after it colonized the tropics.  The genetic evidence suggests the Cuban live oak is derived from the Central American species, but scientists don’t know how the ancestor of the Cuban species made it to the island.  Acorns likely rafted across the Caribbean protected from the salt water in a clump of vegetation.

The genetic evidence suggests the ancestor of the Baja live oak was formerly much more abundant, but the opening of the Sea of Cortez isolated this species.  It shared a common ancestor with the closely related Texas live oak.

Reference:

Cavender-Bares, J.; et. al.

“Phylogeny and Biogeography of the American Live Oaks (Quercus subsection virentes); a Genomic and Population Genetics Approach”

Molecular Ecology 24 2015