Capybaras and Hippos Take II

December 6, 2017

(Note: I tried publishing this post yesterday but due to undetermined technical difficulties the text disappeared.  Hopefully, this entry will have text.)

I planned on writing a blog article about Pleistocene capybaras of southeastern North America, but when I began researching the topic on google I discovered I’d already written a pretty good essay 2 years ago.  (See: https://markgelbart.wordpress.com/2015/12/07/megafauna-habitat-modification-and-pleistocene-capybaras-in-southeastern-north-america/https://markgelbart.wordpress.com/2015/12/07/megafauna-habitat-modification-and-pleistocene-capybaras-in-southeastern-north-america/ ) I’ve written 601 articles for my blog, and it’s hard for me to remember everything I’ve already covered.  Much to my disappointment, there has been little recent academic research about the extinct species of capybaras.  There were 2 species that lived in Florida, Georgia, South Carolina, and probably the Gulf States during the Pleistocene–Neochoerus pinkneyi  and Hydrochoerus holmesi.  Both were more than twice as large as the 2 extant species of capybaras that are presently confined to Central and South America near the equator.  I hypothesize the extinct species could endure somewhat colder air temperatures than their modern day kin due to their larger size.  Nevertheless, they probably extended their range during warmer wetter climate cycles. In my previous blog entry linked above  I think I mentioned how capybaras occupy an ecological niche similar to that occupied by African hippos.  Both are aquatic species that graze adjacent water’s edge marshes into lawn-like environments.  But I didn’t note the remarkable evolutionary convergence in the physical appearance between the 2 unrelated animals.

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Capybara and young.

Convergent evolution is when 2 unrelated organisms evolve similar characteristics to adapt to similar environments.  Capybaras and hippos have similar height to weight ratios.  They also share other characteristics such as small round ears, short necks, square faces, and thick hides.

Hippos remind me of ancient extinct animals from earlier ages…like the kind of monstrous beasts of the Miocene or Eocene.  They should be appreciated for their resemblance to primitive extinct evolutionary dead-ends and ancestral species.  Hippos are most closely related to whales, having shared a common ancestor 28 million years ago known as Epirigenys lokonensis. Hippos resemble the primitive ancestors of whales.

Several extinct species of hippos were widespread in Europe during the Pleistocene but disappeared during the Last Glacial Maximum when available habitat shrank into small refugia where they were more easily hunted into extinction by man. Several species of hippos were also driven into extinction when man colonized Madagascar.  Dwarf species of hippos lived on the Mediterranean Islands of Crete, Cyprus, Sicily, and Malta until man discovered those places.  Just 2 extant species of hippo remain —Hippopotamus amphibious and Hexaprotodon lieberiensis. 

Hippos are the most dangerous non-human vertebrate in Africa.  They are responsible for an average of 2900 deaths every year.  However, mosquitoes and flies spread tropical diseases that kill about 655,000 people annually.  Paradoxically, these tiny pests are a greater hazard than a 2 ton hippo.

 

 

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Surprise: Increased Hurricane Activity During the Younger Dryas

November 28, 2017

 

The vast ice sheet that covered Canada during the last Ice Age began to melt rapidly about 15,000 years ago, creating enormous glacial lakes. The largest glacial lake, known as Lake Aggasiz, was bigger than all of the present day Great Lakes combined.  The ice dam impounding this incredible volume of water collapsed 12,900 years ago, and a massive flood of cold freshwater, icebergs, and debris gushed into the North Atlantic via the St. Lawrence River.  This event caused a sudden drop in global temperatures and a reversal back to Ice Age conditions at northern latitudes because the influx of cold fresh water shut down ocean currents that brought tropically-heated salt water north.  The cold climate phase lasted for about 1500 years, and climate scientists refer to it as the Younger Dryas.

The colder ocean of the Younger Dryas should have spawned fewer hurricanes than the warmer oceans of today.  Hurricanes are a product of energy released from warm ocean water.  However, scientists discovered evidence hurricane activity increased off the coast of Florida during the Younger Dryas.  They discovered deposits of turbidite near the Dry Tortugas Islands, dating to the Younger Dryas.  Turbidite is sediment and rock resulting from underwater perturbations.  Earthquakes can cause turbidite formation, but this region is not prone to seismic activity.  Instead, hurricanes produced underwater currents that formed turbidite here.

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Map of the Dry Tortugas–site of the study referenced in this blog entry.

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Image showing how turbidite deposits are formed.

Scientists aren’t sure why hurricane activity increased during the Younger Dryas at this locality.  Some of their climate models suggest the oceans were much colder to the north and west of the Florida coast but only slightly colder than present day ocean temperatures off the modern Florida coast.  Perhaps the tropically-heated water that pooled near the equator spawned hurricanes that reached the Florida and south Atlantic coasts.

Increased hurricane activity contributed to the expansion of longleaf pine savannahs.  The wind felled forests, and the accompanying lightning-sparked fires maintained longleaf pine savannah ecosystems while repressing closed canopy hardwood forests.  Pleistocene megafauna became extinct during the Younger Dryas, even though longleaf pine savannahs are ideal habitat for grazers such as mammoths, bison, horses, giant tortoises, and many other species.

Reference:

Toomey, M. ; et. al.

“Increased Hurricane Frequency Near Florida during Younger Dryas Atlantic Meridional Overturning Circulation Slow Down”

Geology 45 October 2017

 

 

 

 

The Sitzkrieg Hypothesis

November 21, 2017

The authors of a new statistical analysis of megafauna extinctions boast their method is superior to previous efforts, and they can’t reject human interactions as a cause of the extinctions.  However, they also can’t rule out climate change as a factor, so despite their supposed superior method, their new study (referenced below) resolves nothing.  The statistical method they used is known as kriging, a kind of interpolated algorithm.  The data included 95 of the last radiocarbon dates of megafauna species and 75 of the earliest dated archaeological sites in North America.  They then mapped the last appearance dates of the megafauna with the earliest archaeological evidence of humans.  They concluded climate change caused the extinction of mastodons in Alaska because this species disappeared there long before humans colonized the region, but humans may have been a factor causing extinctions at lower latitudes.  Megafauna persisted until the very end of the Pleistocene in some regions including Mexico, Texas, Tennessee, and the Great Lakes region.  Humans may have overlapped in these regions for as long as 3000 years.  The study doesn’t find much evidence for the blitzkrieg (rapid overhunting) model of extinction, though there may have been “localized” examples of this in western North America.  But it is possible humans gradually disrupted ecosystems in a way that was detrimental to megafauna populations.  This is known as the sitzkrieg model of extinction, and it is the scenario that makes the most sense to me.

There is a major flaw in the reasoning behind the conclusions of this study.  The authors of this study equate the regional disappearance of a species with its extinction.  For example mastodons became extirpated in Alaska about 30,000 years ago, but they did not become extinct.  Populations remained robust south of the ice sheet until about 13,000 years ago.  If man never colonized North America, it seems likely mastodons would have re-colonized Alaska and Canada during the present day interglacial.  Habitat in present day Canada and Alaska is very much like that of some Ice Age regions mastodons formerly inhabited before their extinction.  Mastodons were a wetland species, and aquatic habitats have greatly expanded in Canada and Alaska since the end of the Ice Age.  (During the Last Glacial Maximum Canada was covered by ice sheets and Alaska was an arid grassland–both unsuitable environments for mastodons.)  Climate change may have driven the redistribution of megafauna geographic ranges, but that is not the same as extinction.  During climate phases that favored the expansion of grassland, woodland species were forced to migrate farther to find suitable habitat, and vice versa.  Again, this is not extinction…it is a species adjusting to a new range map.

I’m convinced man, and man alone, is responsible for the extinction of the Pleistocene megafauna.  These wide-ranging species (some occurred all across the continent) were adaptable species that survived dozens, if not hundreds, of dramatic climatic swings over hundreds of thousands of years.  But when man begins to appear in the archeological record, they disappear permanently.  There is no way that can be coincidental. I think man disrupted the ecological balance through a combination of overhunting, increased fire frequency, and interdiction of migratory corridors.  It took a few thousand years, but when human populations reached a certain level, most species of megafauna could not adapt.  They required an ecosystem with low levels of people and did even better with no humans on the landscape at all.

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Graph of average annual temperatures over the past 150,000 years based on data from Greenland ice cores.  Note all of the dramatic climate fluctuations.  Megafauna species survived these climate fluctuations but became extinct in North and South America within a few thousand years of when man entered the continents.

Reference:

Weatherall, M.; Brianna McHorse, and E. Davis

“Spatially Explicit Analysis Sheds New Light on the Pleistocene Megafaunal Extinctions in North America”

Paleobiology November 2017

The Friesenhahn Cave Fossil Site in Bexar County, Texas

November 14, 2017

Rob Nelson stood next to a wall of fossils on 1 episode of Secrets of the Underground, a Science channel tv series.  He was visiting Friesenhahn Cave in Bexar County, Texas about 20 miles north of San Antonio during the taping of the series he hosts.  The tusk of a mammoth or mastodon, a baby mammoth tooth, and many small fossils were visible; and they were cemented together.  It’s remarkable that such an undisturbed matrix could still exist here because people have been excavating fossils from this site off and on for about 100 years.  Specimens collected by local amateurs were first described from this site in a paper published during 1920.  For awhile the landowner stopped permitting people to collect fossils in the cave, but then in 1949 Mr. Friesenhahn himself invited some professors to excavate fossils in the cave. They found the complete skeletons of scimitar-toothed cats and a long-nosed peccary plus the bones of 30 other species of mammals and the remains of reptiles and amphibians. The discovery of the complete scimitar-toothed cat skeletons was important because before this the species was known from an incomplete skull, a few teeth, and some isolated bones.  Large numbers of juvenile mammoth and mastodon bones were found associated with the scimitar-toothed cat skeletons, and the paleontologists came to the conclusion the big cats used the cave as a den and dragged their prey inside.

A flurry of papers about the cave were published, but access was again restricted until Concordia University purchased the property in 1998.  Apparently, since the purchase, some scientists have been working with the disturbed sediments, but they are waiting for a private or government grant before tackling the remaining undisturbed strata.  I suppose they want to use the most modern techniques when going through this material.  During the original dig 68 years ago, scientists mention fossils that were in such poor condition “they weren’t worth preserving.”  (I was appalled when I read this.)  There are modern methods that can preserve fossils that are in poor condition, but they can be costly.  Scientists have also developed better ways of excavating fossils.  Nevertheless, nothing has been published in the scientific literature about this cave since Concordia University purchased the property.  It has been nearly 20 years, and they still haven’t been able to obtain funding for new excavations, though they do have a corporate grant to study the disturbed sediments.  Still, it seems as if someone currently studying the cave would have at least published a paper by now entitled “Additional fossils recovered from Friesenhahn Cave.”  To be honest, I am not impressed with their academic efforts here.

Brief excerpt of an episode of Secrets of the Underground, featuring Friesenhahn Cave.

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A grate protects the cave from looters and keeps trespassers from falling inside.

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The paleontologist, Grayson Mead, with the complete skeleton of a scimitar-toothed cat discovered in Friesenhahn Cave during 1949.

So far, 13 adult and 5 juvenile scimitar-toothed cat remains have been found in the cave.  It’s unclear which of these were recovered in 1949 and which were discovered more recently.  The cave has also yielded 1 bone of a saber-toothed cat, hundreds of baby mammoth and mastodon teeth, the bone of 1 ground sloth; and the remains of bison, deer, camel, tapir, long-nosed peccary, black bear, dire wolf, and coyote.  The latter was especially abundant.  Smaller animals that inhabited the area during the late Pleistocene, based on the bone accumulation in the cave, were jack rabbit, cottontail, desert cottontail, pocket mouse, and 4 species of mice in the Peromyscus genus.  Some of these species are listed in the paleobiology database, and others are mentioned in the below referenced bulletin or on the Texas University website.  The lists don’t match up.  Someone needs to do a more thorough review of the specimens to determine exactly which species were found by whom and during which excavation.

Evidence suggests a pond periodically existed in the cave, depending upon rain and drought cycles. The basin filled during rainy years but dried out during droughts. No fossil evidence of pond turtles exists here.  Instead paleontologists report remains of 2 terrestrial species–a large extinct subspecies of box turtle and an extinct tortoise (Geochelone wilsonirelated to the extinct giant tortoises that ranged throughout the south during the Pleistocene.  G. wilsoni is known from just a few sites in North America but was first discovered in Frisenhahn Cave.  Pond turtles never found the ephemeral water hole in the cave, but northern leopard and barking frogs did. Diamondback rattlesnakes used the cave as a den as well.

The species composition suggests the region around the cave was an arid grassland with some scrub.  Woodlands existed alongside local rivers.  The mammoth, bison, camel, coyote, and jackrabbit indicate dry grassland environments.  However, the presence of deer, tapir, long-nosed peccary, and black bear suggest some woodlands or forest edge habitat existed nearby.

The cave formed when rainwater dissolved limestone rock underground.  The initial entrance was small, and the oldest levels contain small vertebrates deposited in the form of owl pellets.  Gradually, the entrance enlarged so that larger vertebrates began to use it as a den.  Some of the fossil remains are from animals that died in the cave, but others were brought in by predators.  Periodic flash floods may have added small bones to the collection.  Eventually, the cave entrance collapsed, and the chamber was sealed for thousands of years until recent times when a sinkhole formed on top of the cave, allowing modern day access.  The remains are estimated to be 19,000 years old, but it’s unclear where this estimate originated.  I’m unaware of any carbon-dating of the objects in this cave.  It was originally discovered before carbon-dating was invented.  The site is badly in need of a more modern review, and I’m not sure Concordia University is up to the task.

References:

Evans, Glen; and Grayson Meade

“The Friesenhahn Cave” and “The Saber-toothed Cat, Dinobastis serus

Bulletin of the Texas Memorial Museum  September 1961

Secrets of the Underground  Season 1 Episode 5

R.D. Lawrence–Wildlife Writer

November 8, 2017

I enjoy deciphering articles published in scientific journals and translating them into language a layman can understand.  I learned how to do this because of my long fascination with Pleistocene ecology.  Information about Pleistocene ecology almost entirely comes from scientific journal articles, and I found the language in these publications can be unnecessarily complex and oftentimes the writing is just bad.  I had to learn how to interpret them.  Some scientists are good writers, but others are not.  R.D. Lawrence (1921-2003) was a writer who felt the same way I do about language in scientific journals.  At 1 point in his life he was studying to be a biologist.  He wrote a thesis about stickleback fish, and his professor told him it was good, but he wanted him to rewrite it in the language used by scientific journals instead of the easy to understand language Mr. Lawrence had used.  He rejected this “babblespeak” and dropped out of school.  He later wrote 36 books about Canadian wildlife and won 7 awards.

The late R.D. Lawrence relaxing at home with his pet raccoon.

R.D. Lawrence was born in Spain to a Spanish mother and an English journalist who worked for Reuters.  At the age of 14 he was separated from his family during the Spanish Civil War, and he joined the side fighting against the fascists.  (Ironically, his brother joined the fascists.)  Though just a teenager, he led 1 military attack in the sewers against the fascists.  Eventually, he escaped to southeastern France and was later reunited with his family in England.  He fought for Great Britain during World War II.  He was at Dunkirk, rode a tank in North Africa, and was severely wounded during the D-Day invasion.  His injuries ended his military career.  He moved to Canada and worked as a journalist, while studying nature in his spare time.  He gathered enough material so that he was able to start getting his books about Canadian wildlife published.  Recently, I’ve read 3 of his books.

Mr. Lawrence and his wife bought some land in the wilderness of Ontario during 1962.  Here, they built a cabin where they spent weekends.  (He still worked as a journalist during the week.)  He bought the land before most of Ontario was logged over and converted into suburbs, so much of the wildlife was naïve and not particularly afraid of people.  He wrote about his experiences at this cabin in his book, The Place in the Forest.  The semi-tame animals frequenting his cabin yard included red squirrels, fox squirrels, flying squirrels, white-footed mice, snowshoe hares, and birds.  Bird seed and table scraps encouraged the creatures of the forest to hang around the cabin, and if the door was left open, they would enter the cabin and help themselves.  Mr. Lawrence and his wife adopted 2 orphaned raccoon kits and after they were grown and freed, they often returned and joined the feast.  Mr. Lawrence also wrote about some of the less tame inhabitants in the local wilderness–beavers, deer, wolves, black bears, and birds of prey.  He didn’t let worms and insects go unnoticed either.  My favorite chapter relates his encounter with a bald-faced hornet’s nest when he was climbing a tree to photograph a hawk’s nest on another nearby tree.

Mr. Lawrence’s wife died of a brain aneurism at a quite young age, prompting him to move to British Columbia where he decided to buy a boat and travel up the Pacific coast from Vancouver to southern Alaska by himself.  He wrote about this experience in his book, Voyage of the Stella.  When he fished for salmon to eat, he often caught weird species of fish–wolf fish, Pacific lancet fish, barrel eyes, and dogfish. He fed these to the killer whales that occasionally swam near his boat, and he even dove in the water with them while wearing his scuba gear.  The killer whales never bothered him, but he once had to fend off a blue shark.  On his journey he also encountered pods of Dall’s porpoises and a pair of whale sharks.  He refueled his boat at the Indian villages that dotted the coast.  Most of the Indians were friendly, but 1 drunk tried to hit him over the head with a ketchup bottle while he was trying to eat supper at a restaurant. The brave war veteran floored the Indian with an open palm blow to the forehead.

Mr. Lawrence demonstrated even more courage in his next book, The Ghost Walker.  He spent 8 months in a wilderness cabin located in a remote area of British Columbia that was 60 miles from the nearest town, and the only feasible connection to civilization was an hazardous canoe ride down a river.  He used this makeshift cabin as an home base for tracking a large male cougar.  He gained the cougar’s trust, and the big cat let the man follow him around.  Mr. Lawrence experienced several dangerous situations, aside from trusting the cougar not to turn around and eat him.  During a blizzard, Mr. Lawrence sought shelter in a creekside cave but found himself staring eye-to-eye with an hibernating grizzly bear.  Mr. Lawrence popped out of the cave like a “champagne cork” and fled, dropping his backpack which the angry bear tore to shreds. On another occasion he slipped down an icy slope, hit a tree, and sustained a concussion.  He administered his own first aid.  He often tracked the cougar after sunset, walking in the dark woods by himself for hours.  He was 1 brave soul.

I have 1 criticism of Mr. Lawrence.  He imagined he had established ESP connections with a cougar and a killer whale.  There is no rational scientific basis for his belief.  I’m sure it was his imagination, not an ESP connection.  He was just lucky the animals he “communed” with didn’t decide to attack and eat him.

 

The Eurasian and North American Scimitar Cats may have been the Same Species

November 1, 2017

The scimitar cat roamed Eurasia and North America for millions of years until its extinction about 11,000 years ago.  This apex predator sported fangs and was about the size of a lion.  Evidence from Friesenhahn Cave in Texas suggests it preyed upon juvenile mammoths and mastodons as well as peccaries.  A study of bone chemistry in Europe indicates 1 specimen ate yaks.  The scimitar cat is not as well known as the more robust saber-toothed cat (Smilodon fatalis) that apparently was restricted to North and South America.  Another species of saber-toothed cat (S. populator) occurred in eastern South America.  Remains of scimitar-toothed cats are uncommon in the fossil record.  Entire skeletons were found in Friesenhahn  Cave, but elsewhere, if evidence is excavated of scimitar cat, it is usually just a single bone or tooth.  This reflects low populations compared to the prey species it fed upon.  Generally, large carnivores are less common at fossil sites than the species they depended upon for food because predators are necessarily less abundant than their prey.  This low population caused an huge gap in the fossil record of Eurasian scimitar-toothed cats.  There was no evidence of scimitar-toothed cats in Eurasia after 300,000 years BP until the jaw bone of 1 individual was netted by a fishing boat in the North Sea a few years ago. (Much of the North Sea was above sea level during Ice Ages.)  This new specimen dates to 28,000 years BP.  There is also 1 stone statuette that may or may not be of a scimitar-toothed cat–the identification is unclear.  Thousands of generations of this species lived on the continents of Europe and Asia, but this is all the evidence we have of scimitar-toothed cats living there during the late Pleistocene.

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Illustration of scimitar cat.

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This Pleistocene-aged stone statuette may be a representation of a lion or a scimitar-toothed cat.  The deep chin, evolved to protect the fangs, and the bob-tail are evidence it represents Homotherium.  However, the absence of fangs and straight back (Homotherium had a sloping back) indicate it represents a lion.  Unfortunately, this artifact was lost a century ago.

Scientists analyzed the DNA from the North Sea specimen and compared it with the DNA from specimens of scimitar-toothed cats from the Yukon, Canada and some specimens of South American Smilodon populator. They determined the lineage of scimitar-toothed cats (Homotheridae) diverged from the lineage of saber-toothed cats (Smilodontheridae) 18 million years ago.  Despite their similar convergent appearance they were about as closely related to each other as house cats are to tigers.  The genetic study also suggests the Eurasian scimitar-toothed cats (Homotherium latidens) and the North American scimitar-toothed cat (H. serum) should be considered the same species.  The authors of the study found “low genetic diversity despite wide geographical occurrence.”  However, the specimens the scientists used in the study were north and west of the ice sheet that cut most of North America off from Beringia and Eurasia.  Scientists need to study DNA from specimens south of the ice sheet to conclusively show H. latidens = H. serum. A previous genetic study of lions (Panthera spelea, P. leo, and P. atrox) determined North American lions south of the ice sheet were a different species than those north of it.

Reference:

Anton, Mauricio; et. al.

“Soft Tissure Reconstruction of Homotherium latidens (Mammalia, Carnivora, Felidae): Implications for the Possibility of Representation in Paleolithic Art”

Geobios  42 (5) 2009

Paijmans, Johanna; et. al.

“Evolutionary History of Saber-toothed Cats Based on Ancient Metagenomes”

Current Biology (in press)

 

Spider Romance or How to Eat your Mate

October 25, 2017

Halloween decorations often include mock spider webs  because many people think of spiders as creepy.  I don’t.  I think they are fascinating.  There are over 44,000 known species of spiders in the world with about 400 new species named every year.  Most spiders trap their prey in the sticky substance produced in their abdomen, then they quickly pounce on the struggling insect and inject a paralyzing venom that liquefies the insides.  After their prey is subdued the spider sucks the juices from the helpless victim.  I suppose that is an horrifying fate for insects, but people have nothing to fear from such a small organism so vulnerable to a rolled up newspaper.  (I never kill spiders.  Instead, I catch and release them, if they invade my house.)  The spider’s strategy of trapping prey in a web poses a dilemma for males seeking a mate.  It is difficult for a female spider to discern the difference between food and potential sex.  Male spiders must tap on the web in a certain way, communicating to the female they are a sperm donor, not a trapped fly. Mistakes are occasionally made.

Female spiders are larger than male spiders, but in some genera sexual dimorphism is extreme.  Evolution has led to female gigantism among orb-weaving spiders.  Nature has selected for large females and small males in orb-weavers for 4 reasons: a) large females are more fertile and produce more eggs, b) larger females are less likely to fall prey to predators, c) small males reach sexual maturity at an earlier age, and d) small males are better climbers and can reach females faster than others when journeying up the web.  If after sex, a female spider eats a male, there is no great loss.  The female has already been fertilized, and the male is more useful as extra nutrition.  This reproductive strategy is not satisfactory for lampshade spiders.  Female lampshade spiders have larger bodies than males, but the males do have longer legs.  This gives male lampshade spiders the ability to escape after mating, so they can impregnate other females.

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Female and male banana spiders (Nephilia clavipes).  Evolution has selected for large females and small males in spiders.  

Lampshade spiders construct webs in the shape of a lampshade, hence the name.  Females are larger than males in this species as well, but the males have longer legs, so they can escape after mating.

Humans are not as different from spiders as one might think, especially considering risky sex.  People aware of sexually transmitted diseases, including deadly AIDS, are still often willing to have unprotected sex with strangers.  Men and women cheat on their significant others, even though they realize their jealous partner might shoot or stab them, if their indiscretion is discovered.  And some people, mostly men, pay dominatrixes to bind them, putting them in a situation not dissimilar from male orb-weaver spiders.

Many men are attracted to woman who are larger than they are.  My personal preference is for women with really large breasts and buttocks, and I don’t mind if a woman is heavier than I am.  But some men have a fetish for extremely large women…in fact unrealistically giant women, known as giantesses.  They fantasize about a woman who can hold them in the palm of their hand.  The desire male spiders have for gigantic female spiders evidently exists in some human males as well.  Though psychological triggers in the environment probably influence this fetish, there must be something deep inside the mating urge, providing the platform for it to develop in people.  This template is something we share with spiders and likely goes back to a common ancestor over 500 million years ago.

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Many men are turned on by women who are much larger than they are.  Some even fantasize about giantesses.

The association of sexual excitement with fear of being eaten is another characteristic some humans share with spiders and other creatures.  I’m 55 years old, and I thought I was aware of every sexual fetish, but I first learned about the vore fetish within the last year.  Vore is short for devour–some people are sexually excited by the thought of being eaten by their sexual partner.  I don’t really understand this fantasy.  How, for example, does one reach sexual satisfaction after they’ve been eaten?  I think maybe this fantasy has something to do with being in the warm amniotic sac of a woman’s tummy.  Or maybe some are really thrilled with the thought sex might lead to their consumption.  Nevertheless, deep down inside, humans are like spiders in more ways than we would like to admit.

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People are not as different from spiders as one might think.  Some people get sexually excited at the thought of being eaten by their mate.  It’s known as a vore fetish.

Reference:

Kuntac, Matjaz; Jonathan Coddington

“Discovery of the Largest Orb-Weaving Spider Species: The Evolution of Gigantism in Nephilia”

Plos 1  October 2009

The Oak Colonization of North America

October 19, 2017

Oaks are such an important part of the temperate forest ecosystem that it’s hard to imagine they originally evolved near the arctic circle.  During the Eocene about 45 million years ago the earth was mostly tropical and sea levels were much higher than they are today.  There were no ice caps, and climate at the poles was warm and temperate.  Nevertheless, for almost half the year the sun didn’t rise near the arctic circle, just as today night is nearly 6 months long in places like Alaska.  Seasonal darkness led to the evolution of deciduous trees that saved energy by dropping their leaves during winter when the sun didn’t rise.  This adaptation became a great advantage when worldwide climate cooled.  Deciduous trees pushed south because they were able to survive dormant cool seasons that began to occur during the start of the Oligocene ~33 million years ago.  Deciduous trees, especially oaks, replaced tropical species incapable of coping with winter frosts.  Deciduous trees didn’t waste energy with unnecessary growth during winter.

Evidence of the ancient forests where oaks originated exists near the arctic circle at a site known as Axel Heiberg Forest.  Today, this site is a polar desert, but wind erosion is gradually uncovering the forests that existed here 46 million years ago.  A series of floods, perhaps 1 every 10,000 years, covered these forests in sediment, so there are layers of tree stumps, roots, and fallen logs continuously being revealed, as winds strip the sediment away.  Sediment covered the forests rapidly during these catastrophic floods.  It is not a petrified forest because the geological conditions did not favor fossilization.  So once exposed to air, the ancient wood begins to decay, though the process is slow in cold arid conditions.  Scientists think the environment was a warm seasonal rain forest.  Tree composition consisted of dawn redwood, Chinese cypress, hemlock, pine, spruce, larch, gingko, and extinct species of birch, alder, sycamore, walnut, hickory, and oak.

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Location of Axel Heiberg forest–site of the oldest subfossil remains of oaks. Today, it is a polar desert, but during the Eocene it was a temperate seasonal rain forest.

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Subfossil wood from Axel Heiberg forest.

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Comparison between white oak leaves (top) and red oak leaves (bottom).  White oaks and red oaks ecologically complement each other and colonized North America at the same time.

Oaks are classified into 2 groups–red oaks and white oaks.  Genetic evidence suggests red oaks diverged from white oaks about 33 million years ago when they both began to colonize latitudes south of the arctic circle.  Red oaks produce crops of bitter acorns every other year, while white oaks produce more palatable acorns annually.  The strategic difference in acorn production is an ancient ecological balance, attracting squirrels and other seed distributors equally.  Genetic evidence also shows eastern red and white oaks are sister species to western red and white oaks.  Mexican oaks are sister species to eastern oaks, having diverged between 10-20 million years ago.  Oaks colonized eastern and western North America at the same time, then later eastern oaks invaded Mexico.

Mexico has more species of  oaks than any other region in the world (154 species).  If a region has more species of a genus, it usually is thought to be the region where that genus originated.  Instead, scientists believe Mexico has a greater number of oaks species because of differences in elevation in mountains closer to the equator.  Mexican mountains host many different ecological niches causing frequent speciation among oaks.  This explains why Mexico is home to more species of oaks than any other region in the world, though it is not where they originated.

Reference:

Hipp, Andrew; et. al.

“Sympatric Parallel Diversification of Major Oak Clades in the Americas and the Origin of Mexican Species Diversity”

New Phytologist September 2017

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

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