The Co-Existence of Feral Hogs and Peccaries in the Americas

An old episode of Anthony Bourdain’s No Reservations sparked my interest in Brazil’s Pantanal region.  Bourdain searched eastern Brazil in vain for a rare species of fish he wanted to eat.  He was told it was still abundant in a remote part of western Brazil, so he purchased a charter flight to take him there and satisfy his culinary curiosity. The pilot flew the small aircraft through storms, and Bourdain and his crew weren’t sure they were going to make it.  Then, after arrival, Bourdain suffered the worst back pain he’d ever felt, and his producer fell ill with a tropical fever.  Nevertheless, they continued filming and I was impressed with the quantity and quality of wildlife.  It reminded me of 18th century descriptions of Kentucky and early 19th century accounts of Oklahoma.  On a boardwalk through a jungle Bourdain saw a red monkey that no one could identify.  Though there are riverine forests, most of the Pantanal consists of vast treeless plains, variously flooded here and there.  The indigenous people who sparsely populate the Pantanal use it as pastureland, and large herds of feral hogs and peccaries intermingle with cattle.  Caimans and capybaras abound in the flooded parts, and huge flocks of wading birds crowd the water holes.  Incidentally, Bourdain did get to sample the fish.

Map of Brazil’s pantanal.

The Brazilian Panatanal is 1 of the richest wildernesses left on earth.  It encompasses 75,000 square miles and includes at least 12 different types of ecosystems.  463 species of birds, 209 species of fish, and 236 species of mammals live in the region.  It has the healthiest population of jaguars in the world.  Peccaries and wild pigs are the most common ungulates.

Feral hog and vultures feeding upon a dead cow in Brazil’s pantanal region.

Collared peccary.

White lipped peccaries.

Peccaries and pigs are superficially similar in appearance, but they are separated by over 25 million years of evolution.  There are 2 species of peccaries native to the Pantanal–the aggressive white-lipped (Tayassu pecari) and the collared (Pecari tajacu).  Feral hogs (Sus scrofa) are not native to the Pantanal and were introduced hundreds of years ago.  Scientists who study the interrelationships between peccaries and pigs expect the latter to be detrimental to the former, but their studies find this is not true.  A recent study examined the consumption of 37 plant foods among the 3 species, and they found minimal dietary overlap.  Feral hogs favored grugru palm nuts (Acrocomia aculeata), collared peccaries preferred bay cedar (Guazuma sp.), and white-lipped peccaries liked the fruit of a plant in the coffee family (Alibertia sessilis).  All 3 species did feed upon the fruit of Astralea phaleratata, a type of palm.  Palm nuts taste coconut-like.  There was more overlap in diet between white-lipped peccaries and wild hogs than between collared peccaries and wild hogs.  Collared peccaries foraged at times when they could avoid pigs and white-lipped peccaries.

Chart showing diet overlap between the 3 species.  From the below referenced paper.

Palm nuts from the grugru palm are the favorite food of feral hogs in the Pantanal.

Alibertia sessilis fruit ( relative of coffee)  is the favorite food of the white-lipped peccary in this region.

The study determined bay cedar was the favorite food of the collared peccary.

During the Pleistocene new species of mammals periodically crossed the Bering Land Bridge and invaded the Americas, and vice versa.  Like pigs and peccaries, many of the co-existed.  Deer, bear, and big cats came from Eurasia.  Horses and camels went from the Americas to Eurasia.  Co-existence was not always permanent.  Felids from Eurasia outcompeted many species of canids, a group of carnivores originating in North America.  Deer from Eurasia outlasted 3-toed American horses.  The composition of mammals on both continents changed over time, and co-existence between species can be temporary or long lasting.

Reference:

Galetti, M. ; et al

“Diet Overlap and Foraging Activity Between Feral Pigs and Native Peccaries in the Pantanal”

PLOS ONE 2015

 

The Biogeographical History of the Prickly Pear Cactus (Opuntia sp.)

Prickly pear fruit tastes like watermelon but with an even higher ratio of seed to fruit.  They ripen about mid-fall and hang on  the cactus pads through winter when consequently, they often taste like overripe mushy watermelon.  They are high in Vitamin C and anti-oxidants and provide much food energy for humans and wildlife.  I pick them with tongs and use a paring knife to remove the skin and the attached, irritating spines, known as glochids, that don’t seem to stop any creature from eating them.  The prickly pear genus originated in South America, and the seeds, carried in the guts of small and large animals, were transported to North America when a landbridge formed between the 2 continents about 3 million years ago.  Humans have planted them in Africa and Australia where they’ve become an environmentally harmful invasive species.

Opuntia humifusa (eastern prickly pear) in flower.  This species ranges from Florida to eastern Canada.

Eastern prickly pear fruit.  It tastes like watermelon.  During the growing season this species grows upright, but during winter it grows flat on the ground.  The fruit of various species of opuntia can be red, purple, yellow, or even white.

Cactus patches like this are common in Texas.  Texas was a gateway for Opuntia into North America.  Javelina and wild hog spread Opuntia seeds in their dung, and the cactus grows in patches.

During the Pleistocene many Opuntia species evolved to become resistant to frost.  Prickly pear cactus thrives on poor sandy soils because they can retain water better than most other plants.  This would have made them especially well adapted to southeastern North America during arid stadials when sandstorms smothered many square miles of territory.

61 species of prickly pear live in North America today.  Texas hosts the most species–20, while 7 frost sensitive species are endemic or almost endemic to Florida.  An additional 7 species are found throughout the southeast.  2 species are cold tolerant enough to live in Canada.  A study of prickly pear DNA determined that southeastern and southwestern regions of North America provided refuges for prickly pear cactus during the Last Glacial Maximum.  When prickly pear cactus recolonized the midwest and Canada after the retreat of the glacier, closely related species came into conact with each other and hybridized.  This suggests that many more species of Opuntia may be the result of hybridization events that occurred when isolated populations reunited after thousands of years of separation due to climate-initiated environmental changes.  The commercially grown Opuntia ficus-indica is itself a manmade hybrid originally cultivated in Mexico.  Its exact parentage is unknown.  It has been bred to produce large spineless fruit called “tunas.”  I tried growing this cultivated variety from seed I extracted from store-bought fruit, but none germinated.  However, I do have a cactus in a pot that I grew from seed I got from a local wild species–Opuntia humifusa.  This species is quite common in my neighborhood because the soil here consists of Eocene-age sands.

Prickly pear cactus flowers attract all kinds of insect pollinators such as bees, wasps, butterflies, and flies.  Peccaries, deer, ground squirrels, rabbits, skunks, coyotes, foxes, turkeys, box turtles, and gopher tortoises all eat the fruit and spread the seeds in their dung.  Much of Texas’s landscape is covered with cactus patches, probably borne from javelina feces.  Pleistocene megafauna must have created cactus patches across much of the south, especially during dry climate stages when Opuntia was a dominant plant.

Collared peccary (Pecari tagaeu) eating a prickly pear cactus pad.  I thought I’d make it 3 blog entries in a row with something about peccaries by writing an essay about their favorite food.

The cactus pads are also edible, and herbivores sometimes forage on them, but to a lesser degree.  There is less food value in the pads, and the penalty of dealing with spines discourages animals from chewing them down to the root.  Opuntia bugs (Chelindrea sp.), though, plague cactus.  They suck the juice from the pads and can kill the cactus.  Last summer, I thought Opuntia bugs killed the prickly pear cactus I’m growing in a pot, but that tough old cactus did grow back from the roots this winter when the cold weather wiped out their nemesis.

Opuntia bugs (Chelindrea sp.) engaging in sexual intercourse.  There are about as many species of Opuntia bugs as there are of cactus.  They look like squash bugs–the scourge of gardeners.

Reference:

Majore, L.C.; W.S. Judd; P.S. Soltis, and D.E. Soltis

“Cytogeography of the humifusa clad of Opuntia (Cactacaea, Opuntiodoene, Opuntaeae) Correlations with Pleistocene Refugia and Morphological Traits in Polypoid Complex”

Comparative Cytogenetics 60 2012

The Gray Fossil Site in Washington County, Tennessee

In 2000 workers widening route #75 in northeastern Tennessee discovered fossiliferous black soil dissimilar to the red clay dirt commonly found in most of the surrounding countryside.  The highway engineer called in the scientists who soon realized the site was an astonishing treasure of Miocene-age plant and animal fossils.  From the great amount of  data they began uncovering, they knew they could theoretically reconstruct what the entire ecosystem was like then.  The state of Tennessee, home of the infamous and embarrassing Scopes Monkey Trial, took the commendable action of rerouting the highway.  Moreover, in conjunction with East Tennessee State University they built a museum directly adjacent to the site, and now ETSU hosts one of the top paleontology programs in the nation.

Aerial view of the Gray Fossil Site in Tennessee.  I almost visited this museum when I went on my trip to Roan Mountain Bald a few years ago, but I decided not to drag my wife and daughter to yet another museum.

The Gray Fossil Site consists of 2 and probably more filled-in sinkholes.  One sinkhole dates to the late Miocene/early Pliocene (about 7 million-4.5 million years ago), while the other dates to the late Paleocene/early Eocene (about 55 million years ago).  The sinkhole with the Miocene age vertebrate and plant fossils is 220 meters long by 100 meters wide by 36 meters deep.  In ancient times it was a deep but small pond that formed when rainwater caused underlying limestone bedrock to dissolve away.  The structure of the deep sinkhole meant a lot of plant material accumulated on the bottom, creating a poorly oxygenated aquatic environment that prevented the vertebrate bones and plants from decomposing.  Later, the pond filled with sediment, preserving the remains until their discovery a little over a decade ago.  To date only 2% of the site has been excavated, yet over 15,000 fossils have been found here.

There is no radiometrically datable rock at the site, so scientists were forced to use index fossils to estimate the age of the site, explaining the lack of precise dating.  Scientists know the hippo-like rhino (Teleoceras) became extinct about 4.5 million years ago because no specimens of this species have been found at sites younger than that.  A species of short-faced bear (Plionarctos) is unknown from sites older than 7 million years.  These other sites do have radiometrically datable rock.  Thus, that’s the reason for the bracketed dates of age estimation for this site.

The abundance of sticks, acorns, nuts, leaves, pollen, ostracods, snails, and charcoal found at the Gray Fossil Site makes scientists about as excited as the rich assortment of vertebrate bones.  From all this data they can reconstruct a relatively accurate picture of the entire environment here.  One scientist even studied the varves and sediment accumulation patterns to estimate what the climate was like during the late Miocene.  The North American continent during the Miocene, though recognizable to modern geography students, was quite different than that of today.  Most importantly, the Isthmus of Panama had yet to rise above sea level and North and South America were not connected by a landbridge.  Moreover, much of the Rocky Mountains had yet to form.  An important ocean current existed between the 2 continents, and it played a major role in the climate.  The modern Gulf Stream current that keeps the North Atlantic waters warm didn’t exist yet.  Ironically, the Atlantic Ocean was cooler than it is today, but the continents were warmer.  This dramatic difference in temperature between land and ocean caused frequent monsoons during the wet season, but evidence from sediment accumulation suggest the wet monsoon season alternated with a dry, drought-like summer.  However, the climate was stable for millions of years–the continents had yet to drift into the positions that caused cyclical Ice Ages to occur.  Most of North America was tropical or subtropical and frosts at the Gray Fossil Site then were rare to nonexistent.  A temperate forest zone with winter frosts was restricted to northern Canada.

Ocean currents were different before the Isthmus of Panama rose above sea level.  Continental drift eventually joined North and South America, changing worldwide oceanic currents.  This in addition to the collision of India with Asia causing the rise of the Himalayas; and the North American subduction events forming some of the Rocky Mountains contributed to the beginning of Ice Ages.

The Miocene forests formed a continous somewhat homogenous environment all the way across North America, Beringia, and Asia.  Many of the species in Asia and North America were similar and closely related, if not the same.  Palynological studies of the sediment at the Gray Fossil Site show that pine, oak, and hickory made up 90% of the pollen, not unlike that of today’s environment.  Other common plants included elm, sweetgum, fir, hemlock,  walnut, asters (flowers such as sunflowers), and chenopods (spinach, beets, lambquarters, quinoa, etc.).  Macrosfossils of grapes, moonseed, and bamboo show these species were abundant, though the pollen from these plants doesn’t even show up in the pollen analysis.  Many of the species of pine and oak were probably different from extant species.  But the Tennessee State website about the site has a slideshow of Gray site fossils including leaf impressions, and I recognized post oak and southern red oak–2 common species still found in the region.  However, they may have been adapted to different climatic conditions, and if a viable acorn was planted from one of these trees (not likely possible of course), it might struggle to survive in the modern environment because these species have evolved since then to survive in a summer hot/winter cold climate quite different from the Miocene wet/dry seasons with no subfreezing temperatures.

Abundant charcoal and the presence of fossil giant bamboo cane (a fire dependent species) from the site suggests frequent forest fires.  Along with windstorms, this created an environment consisting of a mix of closed and open forests around the sinkhole pond.

Another sinkhole at the site yields botanical evidence of an early Eocene environment.  The area then was dominated by pine, beech, walnut, and aster; though most, if not all, were completely extinct species.

The largest species of mammal to fall into the sinkhole was the gompothere–an elephant-like animal more closely related to the mastodon than the mammoth.  A nearly complete skeleton of a Teleoceras, the hippo-like rhino, was found here.  This very likely was the second largest mammal living in the environment here.

Teleoceras, the hippo-like rhino.  A nearly complete skeleton was found at the Gray Fossil Site.  It was an aquatic species.

A 14 foot tall camel browsed in the Miocene forests.  This giraffe-like animal is known as Megatylopus, and it must have been able to reach leaves and twigs that rhinos, horses, and tapirs couldn’t reach.

Portrait of a Megatylopus drawn by Debbie Kaspari.  What a spectacular beast.

At least 1 species of giant ground sloth occurred here.  Ground sloths originated in South America but found their way to North America millions of years before the Isthmus of Panama rose above sea level.  Scientists think they arrived via a combination of swimming and island-hopping.

By far the most common large animal found at the site is the dwarf tapir (Tapirus polkensis).  Scientists have excavated over 80, a total that surpasses the amount of fossil tapir material found at any other site in the world.  The dwarf tapir was closely related to Baird’s tapir, a species that lives in Central America today.

Photo of Baird’s tapir and young.  This is a Central American species of tapir and the closest living relative to the extinct dwarf tapir (Tapirus polkensis) that was the most common large mammal living in northeastern Tennessee about 5 million years ago.

Three-toed horses were also common, occupying a niche that whitetail deer do today.  They were slenderly built, more like a deer than a horse.  A species of peccary closely related to the modern collared peccary was a component of the fauna.  It was evidentally not related to the long-nosed and flat-headed peccaries–the species that were common in North America during the Pleistocene.  Collared peccaries also expanded their range during warm interglacials of the Pleistocene, but were absent from much of this territory during stadials.

I was surprised to discover that deer were not on the list of species found here. This forested habitat would have been ideal for them.  I contacted a paleontologist who works at the site and noted the lack of deer fossils.  He told me they had discovered a few deer fossils, but they were rare and undescribed in the scientific literature.  He referred me to another paleontologist who would know more about it, but that guy informed me no deer fossils had been found…yet.  So, it’s unclear whether deer fossils are among those found at the site.  Maybe, they don’t want to officially announce the find until someone gets credit for the possible discovery of a new species.  In any case, during the Miocene deer were first starting to evolve.  Later, they spread throughout the northern hemisphere and ecologically replaced 3-toed horses.

Only 2 species of large carnivores have been found at the site.  A tooth belonging to a Machairodus is evidence a fanged cat ancestral to Smilodon and Dinobastis (the scimitar-tooth) hunted here then.  Borophagus, the bone-eating dog, and hyenas would have been 2 additional large carnivores present during the Miocene, but so far, no specimens of them have been found.  The other large carnivore that we know for sure lived here was Plionarctos–a species of short-faced bear that later diverged into the Pleistocene-aged vegetarian Tremarctos floridanus and the carnivorous Arctodus pristinus which then evolved into Arctodus simus.

Two new species of small carnivores were discovered here. I wrote in my blog entry last week that red pandas were discovered here.  I forgot to mention that this species was 4 times larger than modern day red pandas, making them about a 50 pound animal.  A new species of woodland badger (Arctomeles dimolodontus) was found here as well.  It was more closely related to European badgers than to the American species of badger adapted to live in prairie environments.

Dipoides (a species of beaver), swam in the sinkhole pond.  It was closely related to the Pleistocene giant beaver (Casteroides ohioensis), and it did build dams like modern beavers.

The only extinct species of reptile found among the fossils was a type of alligator that appears to have been a transitional species between Olsen’s alligator (Alligator olseni) and the modern American alligator (Alligator mississippiensis).  It was smaller than a modern alligator, growing to less than 8 feet long.  It’s presence is evidence of a relatively frost free climate.  Two species of alligator live in the world today–1 in southeastern North America and the other in China.  Olsen’s alligator is likely the ancestor to both and formerly ranged over an expanded continous range on both continents before climatic conditions deteriorated.  Other species of reptiles and amphibians found at the site are species that are still extant, demonstrating a slow rate of evolution among turtles and frogs.

Skulls of Olsen’s alligator.  This species was ancestral to both American and Chinese species of alligators.  It’ s range was continous over both North America and Asia.

References:

Ochoa, Diana; et. al.

“Palynology of Neogene Sediments at the Gray Fossil Site, TN., USA: Floristic Implications”

Review of Paleobotany and Palynology

Shunk, Aaron

“Late Tertiary Paleoclimate stratigraphy at the Gray Fossil Site (eastern Tennessee) and the Pipe Creek Sinkhole (northcentral Indiana)”

Dissertation

Zobaa, Mohamed; et. al.

“Palynology and Palynofacies Analysis of the Gray Fossil Site, eastern Tennessee: Their role on Understanding the basin-fill history”

Paleogeography, Paleoclimatalogy, Paleoecology 308 (201)

 

The Interglacial Invasion of Warm Climate Species into Southeastern North America

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

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

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

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

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

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

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

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

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

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