Dumpster Dingoes

May 9, 2017

Bacteria. Cockroaches. Flies. And even higher organisms. Mice. Rats. Sea gulls. Crows. Bald Eagles. Cats. Dogs. Wolves. Bears.  These are just some of the organisms that benefit from the food waste produced by humans.  We waste up to 40% of the food we produce.  The proliferation of Homo sapiens since the late Pleistocene has been detrimental to many species, but others have adapted to our presence.  Scientists estimate anthropogenic sources, including livestock and garbage, make up 32% of the worldwide gray wolf diet.  The last surviving population of Asiatic lions almost entirely subsists on livestock.  Studies show Australian dingoes and red foxes that live near landfills have smaller home ranges and higher survival rates than other individuals of the same species.  Dingoes living near garbage dumps grow fat and mate with domestic dogs, producing hybrids that could be called dumpster dingoes.  This same study found black bears foraging around dumpsters have shorter lifespans because they come into conflict with people and get shot.

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Landfills are excellent sites for bird watching.  They attract gulls, crows, and vultures.  I have even seen a bald eagle soaring over one.

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Dogs evolved from wolves that hung around human refuse heaps.

Dingoes are super efficient hunters that prey on almost everything they can kill

Dingo chasing a kangaroo.  Dingoes that hang around landfills get fat and lazy and mate with domestic dogs.

The existence of human refuse heaps likely spurred the evolution of wolf into dog.  The physical characteristics that differentiate dogs from wolves share the same genetic pathway with tameness.  The 2nd and 3rd generations of canids with the least flight response develop the floppy ears and multi-colored coats common in domestic dogs.  Some scientists think it possible some modern day wolves scavenging dumpsters could again evolve into a type of dog.

Genetic studies suggest dogs developed the ability to digest more starch about 4000-7000 years ago–another step in the ongoing evolution of wolf to dog.  This coincides with the development of agriculture when humans began cultivating cereal grains.  Dogs with digestive systems capable of producing more amylase, the enzyme that helps convert starch to sugar, were better able to survive on bread when humans started consuming more cereal grains instead of (or as a supplement to)  meat.

Dingoes descend from dogs brought to Australia about 4000 years ago by people from the subcontinent of India who later assimilated with Australian aborigines.  Dingoes are primitive dogs similar enough to their wolf ancestors that they can revert to the wild and thrive.  Dingoes rapidly became the top non-human predator in Australia.  Most people are unaware dingoes live in America as well. ( See: https://markgelbart.wordpress.com/2013/02/11/the-american-dingo/ ) Native Americans brought primitive dogs with them from Asia, and some of them went wild here just like they did in Australia.  North American dingoes are known as Carolina dogs and were not recognized as a distinct wild canid until a scientist found them running wild during the 1970s on the Savannah River Site in South Carolina.

The observed differences between wolf, dingo, and dog are a good example of recent evolution.  They also show the line between species can be blurry.  All 3 can interbreed and produce fertile offspring.  So some scientists think dogs and dingoes should be classified as subspecies of wolf.  On the other hand the physical and behavioral characteristics of each are quite different, and some scientists still classify them as distinct species.  Domestic dogs are entirely dependent upon humans, dingoes (a transitional form between dog and wolf) can take us or leave us, and wolves avoid us and probably wish humans would become extinct.  I prefer classifying them as separate species based on behavioral differences.

References:

Marshall-Pescini, Sarah; Ingo Besserdick, C. Kratz, F. Rang

“Exploring Differences in Dogs and Wolves’ Preference for Risk in Foraging Trash”

Frontiers in Psychology August 2016

Newsome, Thomas; Gary Ballard, Matthew Crouther, and Chris Dickman

“Dietary Niche Overlap of Free-Roaming Dingoes and Domestic Dogs: The Role of Human-Provided Food”

Journal of Mammalogy April 2014

Oro, Daniel; et. al.

“Ecological and Evolutionary Implications of Food Subsidies from Humans”

Ecology Letters October 2013

 

 

Revisiting Lewis and Clark

May 4, 2017

I haven’t written about the Lewis and Clark expedition before because I try to keep my blog focused on southeastern North America and most of their famous route went through the northwest.  However, the diary of their journey is probably as close as we could ever get to a written account of a theoretical trip by western scientists through a Pleistocene wilderness.  So it is worth covering here.  Lewis and Clark saw western North America when it was thinly populated by Indians and a few white traders.  Humans had not yet completely ruined the environment then.

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Route of Lewis and Clark expedition.

I recently reread the journal of this expedition, and I was struck by how barbaric some of their practices were.  Though this was considered the Age of Reason, they still retained some medieval methods of problem-solving.  Soldiers who broke the rules were whipped.  One man was sentenced to 25 bareback lashes for poor behavior during a social event the night before they began their journey.  Lewis learned enough “doctoring” to be in charge of treating injuries and sick men.  One of his treatments was blood-letting.  At the time physicians wrongly thought bleeding patients could cure certain ailments.  When George Washington was dying of pneumonia his doctors bled him.  Of course, it didn’t work and he died anyway.

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Lewis and Clark engaged in barbaric practices such as blood-letting as a medical treatment and whipping to ensure obedience from their men.

The expedition traveled by sail up the Missouri River, then crossed the Rocky Mountains and sailed down the Columbia River to the Pacific Ocean.  When the wind was unfavorable, they attached ropes to the boat, and the men and their horses pulled the boat upstream.  The company depended upon fish and game for a large part of their diet.  It’s interesting to note how the fish composition changed as the expedition traveled up river.  In the lower part of the Missouri River catfish, buffalo fish, and sucker fish were common.  In 1 beaver pond they netted 318 fish including pickerel, bass, perch, and sucker fish, in addition to crayfish which they called “shrimp.”  In another pond by the river they caught 800 fish over half of which were catfish.  As they advanced up the river they began catching trout, sauger, and goldeye.  Salmon were found in the Columbia River.

 

 

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The Lewis and Clark expedition relied heavily on fish and game while they traveled on the Missouri and Columbia Rivers.  1 single catfish they caught was so big it yielded a quart of oil.

The wildlife was spectacular on the tallgrass and short grass prairies.  In the former they saw deer, elk, and feral horses.  Beavers were abundant all along the river.  The short grass prairie supported large mixed herds of bison, pronghorn, elk, mule deer, and white tail deer.  Lewis reported seeing an herd of 10,000 bison.  Big flocks of white pelicans and geese lived on oxbow lakes.  Grizzly bears were a dangerous problem.  They were difficult to kill with the primitive muskets of the day, and the men had numerous near fatal encounters with them. Cougars were present but rarely seen.  By contrast the expedition found little game when they crossed the Rocky Mountains.

Pronghorn with Bison

Bison and pronghorn.  The expedition often saw large herds of bison, pronghorns, elk, and mule deer together.

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Scene depicting grizzly chasing a member of the Lewis and Clark expedition into water.  Happened more than once.

The expedition brought flour, salt pork, canned soup, and dried corn with them, but they relied more on fish and game.  During winter and spring the animals they killed were often so poorly nourished the only edible part was the marrow bones.  Italians call this “osso bucco.”  In my opinion osso bucco is a fancy name for a dog bone.  Nevertheless, the men relished the fatty marrow. Game was in better condition during summer and fall.  One bison  or 1 elk and 1 deer or 4 deer could feed the expedition for 1 day. Game was scarce in the Rocky Mountains, and they were forced to eat their horses.  They were literally so hungry they could eat a horse.  The food they ate when they traveled down the Columbia River consisted mostly of dog, salmon, roots, and berries.  Most of the men learned to like dog meat, preferring it over venison.  On the coast they purchased whale blubber Indians had scavenged.  They ate wild fruit in summer and fall–grapes, plums, blackberries, blueberries, salmon berries, service berries, and pawpaws.

The Lewis and Clark expedition is credited with discovering 178 species of plants and 122 species of animals new to western science.  The number of animal species they supposedly discovered is wildly exaggerated.  I’ve seen the list, and it includes subspecies of already known species.  They were the first white people to report prairie dogs.  I counted 69 actual species the Lewis and Clark expedition may have introduced to western science.

I wrote a blog article a few years ago about a ring hunt that took place in Pennsylvania during 1760. (See: https://markgelbart.wordpress.com/2014/07/27/the-pennsylvania-mammal-holocaust-of-1760-a-rare-record-of-an-old-fashioned-varmint-drive/ ) Settlers exterminated wildlife in these organized hunts to protect their crops and livestock and starve out the Indians.   One of the animals killed was described as a white bear.  I assumed this was probably an albino black bear or maybe a polar bear that had wandered south.  But I learned members of the Lewis and Clark expedition referred to grizzlies as white bears because some have silver-tipped hairs.  This suggests the white bear killed in Pennsylvania was a grizzly bear that wandered east.  Perhaps, grizzlies occasionally occurred as far east as Pennsylvania during the pre-Colonial era.  Fossil evidence of grizzly bears has been found in Kentucky, but this dates to the Pleistocene.

Bodark Swamps

April 28, 2017

Botanists believe the Osage orange (Maclura pomifera) was restricted to bottomlands along the Red River drainage when Europeans discovered North America.  Here, it grew in pure stands known as Bodark Swamps.  (A disjunct relic population lived in the Big Bend region.) This relative of the mulberry and fig is a shade-intolerant, early successional species capable of surviving flood events that kill competing trees, perhaps explaining why they grow in pure stands. Early settlers cultivated the trees as hedgerows used to confine livestock, and farmers spread this species all over North America.  Osage orange hedgerows were much cheaper than fencing, and they were widely planted until the introduction of barbed wire in 1875.

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Range map of Osage orange.  There were probably additional disjunct relic populations located elsewhere on the continent that were never recorded by botanists.  This species was much more widespread during the Pleistocene.

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Illustration of an Osage orange tree and fruit.

There is some indirect evidence the pre-Columbian distribution of Osage orange was wider than range maps indicate.  Hagen’s sphinx moth (Ceratomia hageni) feeds on Osage orange leaves and nothing else.  This species of moth is locally abundant in the Black Belt prairie region of Mississippi–evidence Osage orange grew on the margin of this natural community before European conquest.  Compact clay soils in the Black Belt Prairie favor grass over trees, and shade-intolerant Osage orange grows well in this environment where they have less competition from other trees. Hagen’s sphinx moth has an erratic distribution.  When agriculturalists were spreading Osage orange seeds it doesn’t seem likely they brought the moths with them.  Relic populations of Osage orange probably occurred wherever this moth is common.

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Hagen’s sphinx moth, aka Osage orange sphinx moth.  Its only host plant is Osage orange.

Osage orange was even more widespread during the Pleistocene.  Mastodon dung excavated from the Aucilla River in north Florida contained Osage orange.  Fossil evidence of Osage orange reportedly was found in Ontario, Canada where it grew during warm interglacial times.  (The oft-repeated source of this information (Peattie 1953) mentions this but doesn’t cite his source.  I consider it a dodgy fact.  Who identified this fossil wood and from what site was it excavated?)  Osage orange became a relic species following the extinction of the mastodon.  A recent experiment determined Osage orange seeds can survive transit through an elephant’s gut but not an horse’s.  (See:https://markgelbart.wordpress.com/2015/04/10/asian-elephants-elephas-maximus-and-horses-equus-ferus-caballus-refused-to-eat-pawpaws-in-a-controlled-experiment/)  Horses and probably tapirs, a relative of the horse, consumed Osage orange, but this large fruit depended on mastodons and maybe mammoths for distribution across the landscape.  Elephants are capable of carrying viable seeds in their guts up to 40 miles before depositing them in great piles of fertilizer.  Without mastodons Osage orange range became more restricted.  Perhaps the Red River drainage and the Black Belt Prairie were where mastodons made their last stand.

Several characteristics of Osage orange show it co-evolved with megafauna.  The large fruits attract big mammals able to efficiently hold and transport the seeds in their guts.  Although horses, deer, squirrels and birds eat the fruit, they either destroy the seeds during consumption or pick at the fruit without distributing the seed.  Osage orange evolved thorns to deter megafauna from chewing on the tree itself.  And if the plant does get eaten, it is able to re-sprout from sucker roots.

Osage orange, along with yew, is considered some of the best wood for making bows.  Some archaeologists believe certain Indian tribes monopolized trade in Osage orange wood.

Osage orange fruit is not toxic, but it is considered inedible for human consumption.  Connie Barlow, author of The Ghosts of Evolution, reports it tastes like air freshener.  Some people think Osage orange fruit can be used as an insect repellant.  However, 1 scientist found 20 insect species on Osage orange fruit littering the campus at Louisiana State University.  The fruit is more likely to attract critters than repel them.  .

References:

Burton, James

“Osage orange: An American Wood”

U.S. Department of Agriculture Bulletin 1973

Ferro, Michael

“The Cultural and Entomological Review of the Osage orange (Maclura pomifera) and the Origin and Early Spread of “Hedge Apple” Folklore”

Southeastern Naturalist (13) Monograph 7 2014

Peacock, Evan; and Timothy Schauwetum

Blackland Prairies of the Gulf Coastal Plain

University of Alabama Press 2003

 

The Pleistocene Great Smoky Mountains

April 23, 2017

I renewed my subscription to the Southeastern Naturalist, so I could read a recent monograph that inventoried the mammal fauna of the Great Smoky Mountains National Park.  According to this paper, 68 species of mammals have been documented in the park, and 1 scientist predicts an additional 4 species might eventually be found there.  I suspect this number is greatly exaggerated–many of the species are small animals not documented in the park since the initial survey when the park was established in the 1930’s.  Those species not documented recently could very well be extirpated from the park.  The flora of the Great Smoky Mountains National Park is impressive but don’t plan a trip and expect to see much wildlife.  I visited the park once and saw just 1 squirrel and no other mammals besides lots of people.  There are 24 species of insectivores and bats allegedly inhabiting the park.  These species are difficult to see and enjoy.  That leaves 44 species and of these only 5 are considered megafauna (animals weighing over 40 pounds). The “big 5” are white tailed deer, elk, black bear, wild boar, and coyote.  The latter 2 are considered invasive, but I think of the coyote as a native species that is recolonizing former territory occupied during the Pleistocene.

There are probably more white tailed deer outside the park in the surrounding farmland.  White tailed deer prefer forest edge habitat, and most of the park has succeeded to old growth.  Elk were re-introduced here in 2001, but they inhabit a small area of the park difficult to access.  The road leading to this spot is a dangerous single lane dirt path on the side of a mountain.  Supposedly, the black bear population in the park is about 1600.  During the summer black cherries (Prunus serotina) make up 25% of the bear’s diet.  Garbage provides 8% of their diet here.  The author of the below referenced monograph claims to have several photographs of cougars taken by park visitors circa 2003.  These may be of captive cougars released by owners who no longer wanted to care for them.  Cougars are normally secretive, and semi-tame cats may have been easier to photograph.  I doubt there is a breeding population of cougars in the park, but I wouldn’t rule it out, and they may eventually recolonize the region, if they keep expanding their range from the west and south Florida.

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Location of the Great Smoky Mountains Park.  The diversity of megafauna species in this park is much lower now than it was in this region during the Pleistocene.

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Strange as it may seem, wild black cherries make up to 25% of the black bear’s diet during mid to late summer in the Great Smoky Mountains National Park.

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The below referenced monograph reports a population of 30 striped skunks inhabit the Cades Cove Campground of the Great Smoky Mountains National Park.  They den in drainage culverts.  Avoid them or you will endure a stinky vacation.

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A fluctuating population of endangered Indiana bats roosts in a cave in Cades Cove.  Bats can be seen at dusk.

The variety and abundance of megafauna in the Great Smoky Mountains National Park is disappointing, but it was spectacular during the Pleistocene.  The natural communities then were similar to those of today, but during cold glacials there probably were more spruce trees and grassy balds and in higher elevations there may have even been tundra-like environments.  Here’s a list of large mammals (based on fossil evidence) that definitely inhabited the park region until ~11,000 BP or beyond.

Jefferson’s ground sloth

Harlan’s ground sloth

tapir

horse

half-ass

mastodon

long-nosed peccary

flat-headed peccary

stout-legged llama

helmeted musk-ox

bison

white-tailed deer

caribou

elk (probably not until 15,000 years BP)

giant beaver

black bear

Florida spectacled bear

giant short-faced bear

cougar

jaguar

saber-toothed cat

scimitar-toothed cat

coyote

dire wolf

Here’s a list of additional megafauna species that likely inhabited the park but whose nearest fossil remains are a considerable distance away.

pampathere

stag-moose

Columbian mammoth

woolly mammoth

Columbian mammoth x woolly mammoth hybrids

gompothere (during warm climate cycles)

giant lion

dhole

The Pleistocene Great Smoky Mountains hosted ~31 megafauna species compared to the present day total of 5.  This is a >80% reduction.  How sad.

Reference:

Linzey, Donald

“Mammals of the Great Smoky Mountains National Park: 2016 Revision”

Southeastern Naturalist 15 Monograph (8) 2016

 

Hares (Lepus sp.) in Southeastern North America during the Late Pleistocene?

April 17, 2017

Librarians can be a pain in the ass.  On 1 occasion I attempted to check out a book from the Augusta College library.  The librarian told me I needed to purchase an alumni card for the privilege of borrowing a book from my alma mater.  I shelled out $25 for the card, and the same #!#!en librarian still wouldn’t let me take the book home.  Another time I was seeking an old Alabama Journal of Science article.  The authors of the article were dead or in a nursing home so I couldn’t get a copy from them.  The journal posts new issues online but not ones this old.  I contacted a librarian from the Alabama library system and asked her to loan the journal to my nearest library where I could pick it up or at least send me a Xeroxed copy of the article.  I offered to pay for postage and use of the copy machine.  She refused because I was not affiliated with the University of Alabama library system.  My efforts to obtain this article have been stymied for 8 years, but I recently learned a surprising tidbit of information from this article that was referenced in another paper I recently came across.  A tooth identified as comparing favorably to hare was found at Bogue Chitto Creek in Dallas County, Alabama; a site where subfossil remains of late Pleistocene species are occasionally discovered.  Bones of hares have been excavated from 7 sites in Florida that date from the Miocene to the early and mid-Pleistocene, but hares are otherwise unknown from late Pleistocene sites this far south, making this an unique find.

Scientists can’t identify this specimen to a species level based on just this single tooth. Bjorn Kurten, co-author of Pleistocene Mammals of North America, states it is difficult to distinguish between rabbit (Sylvilagus sp.) and hare (Lepus sp.)  teeth, and discerning the difference between hare species based on teeth is even harder, if not impossible.  The tooth may have been from a white-tailed (Lepus townsendii), black-tailed (L. californicus), antelope (L. alleni), or an unknown extinct species of jackrabbit that occupied a small geographic range during the late Pleistocene.  This site is probably too far south for another species of hare–the snowshoe (L. americanus).  It’s also possible the tooth is incorrectly identified and belonged to a true rabbit.  Cottontails have long been abundant all over the south, and they are well represented in the fossil record here.  When paleontologists designate a specimen as comparing favorably (cf), they are not 100% certain of the identification.

Map of Alabama highlighting Dallas County

Bogue Chitto Creek, flows through Dallas County, Alabama.  Many Pleistocene fossil specimens have been found in this creek, including the tooth discussed in this article.

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Present day range map of the  black-tailed jackrabbit.  Western species of hares lived in the southeast during the early to mid-Pleistocene.  Scant evidence suggests they may have occurred in the Black Prairie region of central Alabama during the late Pleistocene as well.

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Black-tailed jackrabbit.  Hares differ from true rabbits.  Their young are born with their eyes open and able to hop about and flee from predators.

Bogue Chitto Creek flows through the Black Prairie region of central Alabama.  The compact clay soils here favor grass over trees, and the Black Prairie region itself extends into neighboring Mississippi and Georgia.  Western hare species prefer large treeless plains, and the predominance of this environment here may explain why a relic population of hares existed in this region during the late Pleistocene.  Other environments in the southeast often climax into forests where western hare species can’t survive.  Lagomorphs (hares, rabbits, and pikas) are susceptible to disease outbreaks, and relic populations of hares in the southeast could have easily succumbed to pestilence.  Before I learned about this tooth, I wondered why there was no evidence of hares in the southeast during the late Pleistocene when arid climates led to a greater prevalence of open environments.  This evidence suggests they may have had a local distribution in some parts of the south then.

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Snowshoe hares turn white in winter and brown in summer.

Unlike their western relatives, snowshoe hares prefer forested environments.  A leg bone of a snowshoe hare was found in Cave ACb-2 in Colbert County, Alabama.  This is the southernmost known occurrence of this species, although this is not far from its present day range.  There is anecdotal evidence snowshoe hares occurred as far south as the Great Smoky Mountains National Park as recently as the early 20th century where they possibly still exist today.  Snowshoe hare remains dating to the late Pleistocene have also been found in 2 other southern states–Arkansas and Kentucky.  They require areas with snowpack on the ground for at least part of the year.

Reference:

Ebersole, Jon; and Sandy Ebersole

“Late Pleistocene Mammals of Alabama: A Comprehensive Faunal Review with 21 Previously Unreported Taxon”

Alabama Museum of Natural History Bulletin 28 December 2011

 

Pine Martens (Martes americana) Lived in Southeastern North America during the Late Pleistocene

April 13, 2017

If humans didn’t colonize North America, I believe the pine marten would have a much wider range than it does today.  Presently,  this small carnivore is confined to boreal and mixed forests in Canada, the northern Rocky Mountains, and upper Maine.  In historical times they also ranged into New England.  During the late Pleistocene pine martens lived at least as far south as northern Alabama, and they probably ranged into the piedmont.  (The fossil record of the southeastern North American piedmont region is poor.  I rely on educated speculation to imagine the faunal composition there.)  Pine marten remains dating to the late Pleistocene have been excavated from Cave ACb-2 in Colbert County, Alabama, as well as 2 sites in Tennessee and 2 in Virginia–far south of their present day range.  Pine martens live in low densities, hunting small mammals and birds on the forest floor and in tree tops.  Unlike their relative, the fisher (M. pennanti), pine martens don’t readily re-establish populations after they’ve been extirpated from a certain area.  Archaeological evidence suggests fishers ranged as far south as north Georgia until European colonization when their range was greatly reduced by increased fur trapping, and they thrive wherever they are re-introduced.  But pine martens struggle to increase their populations when they are re-introduced.

Native Americans killed pine martens using deadfall traps.  A heavy rock was propped up by a stick attached to a piece of meat with a string.  The rock crushed the pine marten pulling at the bait.  Pine martens often fail to replenish their populations after humans begin trapping them in a certain area.  They’ve been able to survive in Canada because this region is more sparsely inhabited by people.  The denser population of humans in the southeast not only trapped out the pine martens but planted agricultural fields and cleared the deep forest habitat they require.  Humans can be just as detrimental to some species of small animals as they are to megafauna populations.

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Pine marten. They are about the size of a small house cat.

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Present day range map of the pine marten.  Most of this range was under glacial ice during the Ice Age.  However, they lived south of the ice sheet at least as far south as Alabama.

Map of Alabama highlighting Colbert County

Fossil evidence of pine marten was found in Cave Acb2 in Colbert County, Alabama.  This is its southernmost known occurrence.

Some scientists speculate evidence of pine martens in north Alabama during the Ice Age suggests the region was covered with boreal spruce forests because this is the type of environment where pine martens occur today.  As I’ve noted in previous blog entries, the Ice Age forest that existed in the upper south then was likely a mixed forest consisting of an extinct temperate species of spruce (Critchfield’s) and hardwoods such as oak, hickory, walnut, elm, etc.  Temperatures were only slightly cooler in this region then than they are today.  I believe humans, not climate change, are the reason for the pine marten’s range reduction.

Reference:

Ebersole, Jon; and Sandy Ebersole

“Late Pleistocene Mammals of Alabama: A Comprehensive Faunal Review with 21 Previously Unreported Species”

Alabama Museum of Natural History Bulletin 28 December 2011

Ice Age Western Lakes and Altered Bird Migrations

April 9, 2017

I photographed a lesser yellowlegs (Tringa flavipes) at Woodbridge Lake, Evans, Georgia last weekend.  I was thrilled to see this transient species in such an unexpected locality.  Lesser yellowlegs and many other species of sandpipers spend the winter in South America, Florida, and the coasts of Georgia and South Carolina, but they migrate to their summer breeding grounds in western Canada during spring.  The present day breeding grounds of 22 American species of sandpipers, plovers, curlews, and dowitchers were mostly or completely under glacial ice during Ice Ages.  One might ask where these species bred during Ice Age summers.  Weather patterns were much different then.  Today, much of the west is arid desert, but during Ice Ages the region enjoyed a cooler and much wetter climate.  Many large lakes existed in western North America, and they provided beach, reedy marsh, and open water habitats for aquatic birds.  A large prehistoric body of water, known as Pleistocene Lake Manix, covered what today is the Mojave Desert, and Pleistocene Fossil Lake inundated the modern day site of a desert in central Oregon.  Both of these sites yield abundant remains of the aquatic bird species that formerly spent all or part of their lives there.

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Map of western North America during the Ice Age.  More precipitation and cooler weather patterns resulted in large lakes in place of present day arid landscapes.

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Lesser yellowlegs in Evans, Georgia.  This species is a transient here.  It spends winters in South America, Florida, and the southeastern Atlantic Coast, but breeds during summer in western Canada.

Lesser Yellowlegs Range Map

Range map for a lesser yellowlegs.  Many species of sandpipers have similar ranges.  Almost their entire breeding range was under glacial ice during Ice Ages.  They shifted their breeding ranges to the lakes in western North America that no longer exist and are deserts today.

The entire breeding range of the white fronted goose, the blue goose, and 10 species of ducks was also under glacial ice during the late Pleistocene.  The geese and some species of ducks shifted their breeding ranges to these western lakes.  However, harlequin, eider, king eider, and the extinct Labrador duck have/had more easterly distributions and likely bred near the Atlantic coast south of the ice sheet.  Other migratory species of birds that bred on western lakes during Ice Ages include whooping cranes, northern skuas, and arctic loons.

Many species of aquatic birds that breed in western Canada during summer still breed in western states as well wherever wetlands still exist.  Instead of shifting their breeding ground migration north, these species expanded their summer breeding grounds but still also nest within their Pleistocene range.  This list of species includes 2 loons, 2 grebes, white pelicans, 2 swans, 10 ducks, sandhill cranes, Virginia rails, Hudsonian godwits, American avocets, 3 phalaropes, and 3 jaegers.

The abundant large lakes of Pleistocene western North America attracted some species of non-migratory birds that no longer occur in the region.  Anhingas are fish-eating birds confined to southeastern North America today, but fossil evidence shows they lived in Oregon during the Ice Age.  The beautiful scarlet ibis no longer occurs north of Central America but ranged to Oregon then also.

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The scarlet ibis no longer occurs north of Central America but did live as far north as Oregon during Ice Ages.

Western lakes evaporated and turned into desert following the end of the Ice Age.  A number of species failed to adapt by shifting their ranges to newly available Canadian habitat, and they became extinct.  The extinct species include a flamingo, 2 gulls, a jaeger, a cormorant, a grebe, a swan, a goose, and a shelduck.

Breeding colonies of aquatic birds attract predatory species such as bald eagles and great horned owls.  Fossil evidence of both these species is found at most of the sites of these former Pleistocene lakes.

The extinct western lakes would have been a birder’s paradise. Paleo-indians saw the wealth of avifauna as a food source.  Paleo-indians had no television, radio, and little in the way of entertainment, so perhaps bird-watching was a leisure activity for them after they filled their bellies with spit-roasted duck.

Reference:

Jefferson, George

“Remains of the Late Pleistocene Avifauna from Lake Manix, Central Mojave Desert, California”

Bulletin of the Natural History Museum of Los Angeles County June 1985

The Disappearance of the Dickcissel (Spiza americana) from the Mid-Atlantic States

April 4, 2017

The dickcissel is a cyclically abundant grassland bird that spends its summers in North America and flies to South America during winter.  They feed upon grass seeds, though they give their young high protein insects in spring.  Their nests are hidden in tall grass.  Dickcissels are found associated with other grassland species of birds such as meadowlarks, red-winged blackbirds, vesper sparrows, grasshopper sparrows, and savannah sparrows.  Dickcissels prefer clover and alfalfa pastures and old abandoned fields, but they don’t like suburban habitat.  The heart of dickcissel range is the agricultural Midwest.  Migrating stragglers may occur on the Atlantic coast today, but mysteriously, large breeding populations of dickcissels invaded the mid-Atlantic during the middle of the 19th century and just as mysteriously they disappeared from this part of their range by 1900.  Maybe farmers in this region planted more corn and less wheat and clover fields.  Corn rows don’t offer usable habitat for dickcissels.

Summer range map of the dickcissel.  It breeds in the dark red area but vagrants are found within the dotted lines.  They formerly bred in the mid-Atlantic states from South Carolina to Massachusetts.  Stragglers migrate south along the Atlantic coast.

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A pair of dickcissels.  They are a type of finch.

Dickcissels likely were cyclically abundant during the Pleistocene as well with widely changing geographic ranges.  Studies show dickcissels are eliminated from ranges that are burned, and their numbers decline in areas where bison graze.  This suggests they bred on grasslands temporarily abandoned by grazing megafauna herds and left untouched by fire for at least a year.  Lightning-ignited wild fires were less frequent during colder climate phases of Ice Ages.

As far as I can determine, dickcissel remains have been excavated from only 1 Pleistocene-aged fossil site–Little Box Elder Cave in Wyoming, a site just outside the periphery of their modern day range.  (Little Box Elder deserves a blog entry of its own.  Remains of at least 62 mammalian species were recovered here including horse and the only known association of grizzly and short-faced bears south of the former ice sheet.)  Although dickcissels are known from just this 1 fossil site, they may have been common during some climatic stages of the Pleistocene.  I believe they are rare in the fossil records because they inhabit open grassy areas where their remains are not likely to be preserved.

Little is known abut the dickcissel’s past.  Scientists could use genetic analysis to determine historic and pre-historic population dynamics and their evolutionary relationships to other members of the Cardinalidae family which includes cardinals, grosbeaks, finches, and buntings.  Maybe some day, they will be able to explain why the dickcissel disappeared from mid-Atlantic sites.

The Ghost Boundary of the Last Glacial Maximum Ice Margin

March 30, 2017

The southern margin of the Laurentide Ice Sheet is still evident today in the range maps of at least 19 species of eastern trees.  During the most recent Ice Age about 20,000 years ago glaciers advanced to their farthest extent, a time period known as the Last Glacial Maximum (LGM). This giant sheet of ice pushed boulders, obliterated forests, and even blocked and bent major rivers.  After the glacier began retreating many species of plants colonized the nearby deglaciated territory, but 19 species of trees never advanced and remain locked in the same ranges within which they probably occurred during the Ice Age.    Though the ice margin is long gone it still marks the northern limit of these trees, serving as a kind of ghost boundary.

A majority of paleoecologists long thought a boreal forest consisting of spruce and northern species of pine existed for hundreds of miles south of the ice sheet during the LGM. Studies of fossil pollen abundance deceptively support this belief.  Spruce pollen dating to the LGM predominates in sites as far south as north Georgia.  But spruce and pine trees produce more pollen than oak and other hardwood species. Moreover, spruce and pine pollen is more resistant to decay, so oak pollen is likely underrepresented in samples.  The range maps of the below listed 19 species suggests they occurred all the way up to the ice margin during the LGM.  The forest that existed immediately south of the ice sheet during the Ice Age was probably a strange mix of spruce and hardwood trees not found in any extant natural community.  Sweet gum, post oak, and river birch grew side by side with white spruce and fir.    Scientists refer to this unusual plant composition as “non analogue” communities.  Farther south, spruce pollen excavated from fossil sites likely originated from the extinct temperate species–Critchfield’s spruce.

Below is the list of 19 species whose northern range limit reaches the ghost boundary of the Laurentide Glacier.  This list is from the below referenced study.

shortleaf pine (Pinus echinata)

Virginia pine (P. virginiana)

pitch pine (P. rigida)

sourwood (Oxydendrum arboreum)

willow oak (Quercus phyllos)

southern red oak (Q. falcata)

swamp chestnut oak (Q. michauxii)

overcup oak (Q. lyrata)

post oak (Q. stellata)

yellow buckeye (Aescules flava)

river birch (Betula nigra)

persimmon (Diospyros virginiana)

pecan (Carya illinoinensis)

pumpkin ash (Fraxinus profunda)

sugarberry (Celtis laevigata)

winged elm (Ulmus alata)

sweetgum (Liquidamber styraciflua)

white basswood (Tilia heterophylla)

black locust (Robinia pseudoacacia)

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Map of the Laurentide Ice Sheet.  The northern limits of at least 19 species of eastern trees coincides with the ice margin of this glacier where it advanced during the Last Glacial Maximum about 20,000 years ago.

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Range map of shortleaf pine.   The northern limit of this species closely coincides with where the southern lobe of the Laurentide Glacier advanced.

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Sourwood range map.

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Willow oak range map.  Note how it grows to southern New Jersey, just short of where the ice sheet advanced.

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Yellow buckeye range map.

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Sweetgum range map.

When I was researching this blog article, I discovered a 20th species that might be added to this list.  Blackjack oak (Q. marilandica) is a small scrubby oak that grows on poor sandy soils.  The northern limit of this species range also is nearly identical with the ghost boundary of the Laurentide Glacier.  However, there are 2 small disjunct populations of this species in southern Michigan.  Unlike the other 19 species on this list blackjack oak must have temporarily colonized deglaciated territory, thriving on poor gravelly soils recently scoured by glaciers.  After soil improved other species outcompeted blackjack oak over most of the Midwest, but it remains in locally favorable habitat

Reference:

Loehle, C; and H. Iltis

“The Pleistocene Biogeography of Eastern North America: A Nonmigration Scenario for Deciduous Forest”

U.S. Department of Energy Technical Report 1998

https://www.osti.gov/scitech/biblio/564104

The Sourwood-Lettered Sphinx Moth-Black Bear Food Web

March 26, 2017

There are many intricate relationships between different species of plants and animals yet to be discovered.  The interrelationship of sourwood (Oxydendrum arboreum), lettered sphinx moth (Deidami inscripton), and black bear (Ursus americanus) was first noted in the scientific literature just last year.  Sourwood is a small tree, seldom growing to over 6o feet in height, that lives in oak forests and woodlands with acidic soils.  It is the sole species in its genus and a member of the blueberry and azalea family.  The leaves have a sour taste and can be chewed but shouldn’t be swallowed because they are mildly toxic with a high amount of oxalates.  Scientists were studying the occurrence of a major defoliation event of sourwood trees near Unicoi, Tennessee a few years ago.  Here, sourwood trees along with dogwood, summer grape, Virginia creeper, and greenbrier form the understory of a forest composed of red maple, black gum, northern red oak, pitch pine, Virginia pine, chestnut oak, scarlet oak, and striped maple.  They found the sourwood trees were being defoliated by larva of the lettered sphinx moth.

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A sourwood tree in fall foliage.

Lettered Sphinx - Deidamia inscriptum

The lettered sphinx moth.

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The larva of the lettered sphinx moth feeds upon grape, Virginia creeper, and peppervine; but just recently was discovered to have a preference for sourwood over all those plants in the Vitis family.

The lettered sphinx moth is the only species in its genus that lives north of Mexico.  Lettered sphinx moth larva were known to feed upon the leaves of plants in the grape family which also includes Virginia creeper and peppervine.   Lepidopterists refer to these plants as “host species.”  However, when scientists discovered sphinx moth larva defoliating sourwood they conducted an experiment–they put sphinx moth larva in terrariums and offered them grape leaves and sourwood leaves.  The sphinx moth larva preferred the sourwood leaves.  This suggests sphinx moth larva will choose sourwood leaves wherever the ranges of sourwood and species in the grape family overlap.

Scientists hypothesize the oxalates ingested from the sourwood accumulates in the caterpillar, and the toxicity discourages avian predators.  Nevertheless, bears are able to eat the caterpillars.  The authors of the below referenced study found evidence bears were consuming large quantities of sphinx moth caterpillars during the defoliation outbreak.  They saw stem breakage, claw marks on limbs, and bear scat filled with caterpillar remains all around the sourwood trees.  Moth larva provides lots of protein and fat, and the partially digested plant material in their guts likely contains beneficial vitamins for the bears.  The bear scat in turn helps fertilize the soil around the sourwood trees.

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Black bear feeding on forest tent caterpillars.  Caterpillars are nice fatty snacks for the bruins.

The interrelationship between sourwood, sphinx moths, and bears probably began during the Pleistocene or perhaps earlier; but it wasn’t noticed or recorded by people until last year.  There are countless other examples like this, yet to be discovered.

Reference:

Levy, Foster; David Wagner and Elaine Walker

“Deidamia inscripton (Lettered Sphinx Moth) Caterpillars feeding on Oxydendrum arboretum (Sourwood) and their Predation by Black Bears in Northeastern Tennessee”

Southeastern Naturalist 15 (3) 2016