Pleistocene Megafauna Wallows and Southern Appalachian Bogs

The wallowing, trampling, and foraging of Pleistocene megafauna probably maintained the open character of mountain bogs in the southern Appalachians during the Ice Ages.  Bogs were common natural environments during moist interstadials when cool temperatures reduced evapotranspiration rates and total precipitation increased.  Bogs occurred near the headwaters of mountains rivers and upper piedmont streams on flat poorly drained sites.  Boggy communities were “embedded” in mixed forests of pine, spruce, oak, and beech; and they provided a diverse array of habitats for wildlife.  Beavers created some bogs by damming streams.  The backwaters flooded depressions created by the wallowing activities of mastodons, horses, bison, peccaries, and possibly the extinct stag-moose (Cervalces scotti).  Scientists don’t know whether Cervalces scotti wallowed or not–some species of deer such as the present day moose wallow while other species do not.  Abandoned beaver ponds succeed to wet meadow communities consisting of herbs, grass, and sedge; thus attracting additional herds of megafauna that continued to maintain the open nature of the bog.  These vast wet meadows were ideal habitat for the extinct giant beaver (Casteroides sp.); a species that preferred to eat softer vegetation than its present day cousin.  Eventually megafauna herds migrated away and shrubby vegetation took over, creating yet another type of habitat.  Then, the shrubs gave way to trees such as red maple, sweetgum, tulip, black gum, pitch pine, and oak.  Beavers returned, removed trees, made dams, and the cycle began anew.

moose wallow

Moose wallow.

Picture showing Sweetgale Fen community

Sweetgale Fen in Maine.  This is a shrub-dominated fen.  Shrub and grass-dominated bogs may have been common in the upper south during moist but cool interstadials of the Pleistocene.

Bogs are replenished by precipitation.  During really dry cold phases of Ice Ages many of them dried up, but this type of environment never disappeared completely.  Cool temperatures slowed evaporation, allowing bogs to remain in mesic localities.

Bogs are acidic environments where sphagnum moss grows.  They differ from wetlands known as fens that are fed by groundwater.  Fens host neutral or alkali soils.  There are no true fens in Georgia because groundwater seeps through acidic bedrock.  The nutrient poor acidic soils of bogs support many interesting plants such as purple pitcher plant, alder, azalea, mountain laurel, cranberry, and blueberry.  They are all well adapted to poor acidic soils.  Pitcher plants obtain nitrogen from insects they trap in their leaves.  Alders can fix nitrogen from the atmosphere.  Members of the heath family (mountain laurel, azalea, blueberry, cranberry) have a symbiotic relationship with underground fungi that helps them extract nitrogen from soils with low levels of this element.

Mountain bogs are rare in Georgia today because they occurred on flatlands that were soon cultivated by European settlers.  A few still exist in Rabun and Union Counties.  They provide habitat for some bird species presently considered rare in the state including ruffed grouse, woodcock, and willow flycatcher.  This indicates these 3 species were abundant in the southern Appalachians during Ice Ages when bogs were more widespread.

Large mammals wallow in mud to rid themselves of parasites.  After the mud dries they scrape off the dirt by rubbing against trees or large boulders.  They wallow in the same places, creating depressions that alter drainage patterns and plant species composition.

Youtube video of an elephant wallowing.

I assumed all traces of megafauna wallows have disappeared over time, but E. Breck Parkman, a California archaeologist, believes he’s found an old megafauna wallow.  The site is known as the Mammoth Rocks and is located in northern California near the coast.  He’s found a depression next to the rocks.  He thinks this depression was used as a wallow, and the mammoths rubbed the mud off on the adjacent rocks.  He also thinks California’s vernal pools, an environment of mysterious origin, were former megafauna wallows.  Other potential “rubbing rocks” have been found in New Mexico, Texas, Minnesota, and Wisconsin.  It may be possible that Pleistocene-aged megafauna wallows may be present in Georgia.  Unusual depressions next to exposed rocky outcrops may be wallows.  However, paleo-wallows in Georgia are probably difficult to find and decipher.  Most have been filled with organic sediment, and many have been obliterated by agricultural practices.  Moreover, trees were more abundant than rocky outcrops.  Trees rubbed by extinct megafauna have long ago decayed to soil.

Mammoth Rocks

An archaeologist believes mammoths wallowed in this depression and used the rocks to rub off the caked dirt.  This site is known as the “Mammoth Rocks” and is located in northern California.  During the Pleistocene this region was a coastal prairie farther above sea level than it is today. Paleo-wallows like this may exist in southeastern North America but are probably harder to find because megafauna used trees instead of rocks to rub off dried mud.

Reference:

Edwards, Leslie; and Jonathan Ambrose and L. Katherine Kirkman

The Natural Communities of Georgia

The University of Georgia Press 2013

http://www.parks.ca.gov/?page_id=23566

 

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2 Responses to “Pleistocene Megafauna Wallows and Southern Appalachian Bogs”

  1. George Crawford Says:

    Reblogged this on BLACKWATER DRAW LOCALITY 1 and commented:
    Interesting thoughts ahead, or jump to the associated paper here: http://www.parks.ca.gov/?page_id=23566

  2. markgelbart Says:

    Thanks.

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