Posts Tagged ‘white-tailed deer’

Pleistocene Ungulates of Interstadial Oak Woodlands and Forests in Southeastern North America

November 4, 2016

I have long been curious about the wildlife I would encounter, if I could travel in a time machine to a wilderness cabin located in central Georgia 36,000 years ago.  This climatic stage was an interstadial–a relatively warm wet phase of the Ice Age.  It was likely well before people entered the region, so I could experience an ecosystem completely uninfluenced by man.  Pollen evidence from deep ocean cores suggests an expansion of oak woodlands and forests during interstadials, while pine and spruce declined.  (Botanists distinguish the difference between woodland and forest.  A woodland has 50%-80% canopy coverage; a forest has >80% canopy coverage.)  Oak woodlands were probably the most common natural community in the Georgia piedmont during interstadials.  They had an open structure with centuries-old, large diameter trees in the overstory and herbaceous and grassy understories.  Megafauna trampling and foraging along with low intensity fires and occasional windstorms maintained the open structure of the woodlands.  Areas less frequented by megafauna and protected from fire fostered thicker forests.  Oaks dominated the landscape but co-occurred with hickory, chestnut, and pine.  The warmer the climate phase, the greater the variety of trees.

Oak woodlands provided ample food for a large population of animals.  Acorns and plants growing in the understory fed herds of ungulates as well as bears, small game, and birds.  Bison, horses, and mammoths prefer(ed) prairies and meadows, and mastodons foraged alongside streams.  Although these species occasionally wandered into woodlands, they were probably less common than other species of ungulates in this environment.  Instead, ungulates that fed mostly on forest vegetation prevailed in oak woods.  Studies of bone chemistry that determined dietary preference suggest forest denizens included white-tail deer, long-nosed peccary, tapir, and paleollama.  These are the ungulates I would expect to see from a window in my imaginary wilderness cabin.  Fossil remains of paleollama ( Palaeolama mirifica) have not been found north of the coastal plain, but they may have ranged into the piedmont.  Its cousin, the large headed llama ( Hemiauchenia macrocephela ), was more widespread and isotopic studies indicate it could subsist on either prairie or forest vegetation.  The presence of at least 1 species of llama in central Georgia seems likely.  And of course herds of ungulates attracted a whole array of predators.  The woods of today seem so destitute by comparison.

DNR Camera Project

 

 

 

 

 

10 white-tail deer and a turkey.  This species of deer and its immediate ancestor have populated southeastern North America for millions of years.

Long-nosed peccary.  The success of invasive wild hogs shows that forest environments in the south can support a large population of pig-like animals.

Mountain tapir and young

Mountain tapir with a baby.  Tapirs that lived in the upper south during the Pleistocene likely were adapted to temperate climates like this species.  Isotopic studies of tapir bones indicate they preferred the thickest part of the forest.

Paleollamas of the Pleistocene Period in Florida.

Paleollamas.  They occurred in Florida and the coastal plain and may have ranged into the piedmont.  This species of llama also preferred deep forest, but its cousin, the large-headed llama, was more adaptable.

 

Llama and Deer Abundance during the Pleistocene in Southeastern North America

September 16, 2015

Studies of bone chemistry suggest the species of North American llamas that lived in North America during the Pleistocene enjoyed a diet similar to that of the white-tailed deer (Odocoileus virginianus).  The species of llamas that co-existed with deer then were the large-headed (Hemiauchenia macrocephala) and the stout-legged (Paleolama mirifica).  Evidence determined from the below referenced studies suggests the large-headed llama preferred open woodland habitat because it was a mixed feeder capable of grazing grasses and browsing on trees and shrubs.   One scientist thinks they may have grazed on green grass during the summer and browsed on woody vegetation during the winter.  In any case it was a very adaptable species with a wide geographic and temporal range, having existed for over 2 million years.  The stout-legged llama was a denizen of deep forests, dependent upon browsing the plant foods found in shady environments.  White-tailed deer are also browsers that prefer deep forest and forest edge.  I’ve considered the ecological interrelationship between Pleistocene llamas and deer and have reached some hypothetical conclusions about the former abundance and distribution of each species.

Llama, deer | by mezzoblue

Llama and deer on a farmed ranch.  Llama and deer co-existed in southeastern North America during the Pleistocene and consumed many of the same plant foods.  Llamas are closely related to camels.

The large-headed llama was probably far more abundant in Florida during the Pleistocene than white-tailed deer based on the abundance of each in the fossil record.  The former species has been found at over 60 fossil sites in Florida.  Remains of this species have been found off the coast of Georgia (which was above sea level during glacial episodes) as well as the coastal plains of South Carolina and Texas.  The large-headed llama also ranged from southern California north to Washington, Idaho, South Dakota, and southern Canada.  Their range included Oklahoma, Kansas, and Nebraska as well.  Curiously, no certain remains of this species have been found from central Georgia north to Wisconsin and Maine.  Clayton Ray, former curator for the National Museum of Natural History, commented that a partial tooth found at Ladds in Bartow County, Georgia resembled a “camelid” but was not enough evidence to definitely state the presence of llamas there.  Based on the geographical occurrence of this species’ remains and isotopic evidence suggesting it preferred open woodlands, I’ve concluded its Pleistocene range extended from western North America to the southeastern coastal plain and Florida.  Many species of western plants are found on the southeastern coastal plain where they occur as relics, and this is evidence an ecologically similar corridor once connected western prairies to southeastern savannahs.  The large-headed llama likely was a common animal of long-leaf pine savannahs that formerly prevailed on southeastern coastal plains.  Their fossil remains are so common at the Harleyville fossil site in South Carolina that it is known as “camelot.”  This site dates to 400,000 years ago before bison colonized the region.  Llamas had even less competition for food during the middle Pleistocene.

White-tailed deer and long-nosed peccaries (Mylohyus nasatus) were likely the most common hooved animals in north Georgia during the late Pleistocene based on their abundance in the fossil record here.  This is evidence that forests grew more dense to the north of the coastal plain.  There is not enough fossil or pollen evidence to determine where exactly in the piedmont forests began to become more dense.  The latitude where the density of the canopy increased from open woodland to closed forest fluctuated depending upon climatic cycles and other factors.  Despite the lack of fossil evidence, I believe large-headed llamas occasionally ranged into the piedmont and mountain regions of the south whenever habitat became favorable.  They advanced wherever forests became more open.  But deer were probably more common than llamas in the upper south for most of the Pleistocene.

Fossil remains of the stout-legged llama seem to be restricted to Florida and the coastal plain of Texas south to South America.  This suggests the stout-legged llama was not as cold tolerant as its cousin.  Instead, they preferred warm sub-tropical forest.

Both species of North American llamas were 2 to 3 times larger than white-tailed deer.  Large-headed llamas grew to 660 pounds, while stout-legged llamas reached 600 pounds.  Their larger size meant they reproduced more slowly than white-tailed deer and were less able to withstand human hunting pressure.  Changing climatic conditions could not have caused their extinctions because the foods they ate always remained abundant.  White-tailed deer populations, especially in Florida but wherever their ranges overlapped, increased following the extinctions of llamas because they no longer had to share the edible plant material the environment provided.

References:

Kohn, Matthes; and M. McKay

“Dining in the Pleistocene: who’s on the menu”

Geology 33 (8) 2005

Yann, L.; and L. Desantis

“Effects of Pleistocene Climates on Local Environments and Dietary Behavior of Mammals in Florida”

Palaeogeography, Palaeoclimatology,  Palaeoecology 2014