Archive for April, 2017

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

 

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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.