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Wildlife Extinctions, Dwarfing, and Redistribution During the Early Holocene

The profound changes that were occurring in vegetation as the glaciers retreated also impacted wildlife species. Some wildlife species that were part of the southeastern Ice Age landscape became extinct or migrated to other regions, or out of North America entirely.

Faunal extinctions toward the end of the last glacial period (Pleistocene) and continuing into the Holocene were not the first wave of extinctions. According to Pielou (1991), at least six waves of extinctions have occurred during the Earth's history. Many of the extinctions have occurred at the end of glacial periods. The sixth wave ranked second in number of species extinctions and occurred at the end of the Pleistocene (Pielou 1991). Estimates of extinctions of mammals and birds between 20,000 to 7,000 years BP are as high as 17 genera (Hester 1960, Steadman and Martin 1984). The greatest numbers of extinctions occurred between 11,000 to 10,000 years BP (Martin 1967).

A number of paleoecologists have developed environmental models that depict rapidly changing ecosystems at the end of the Pleistocene as the cause of wildlife extinctions (Guilday 1982, Guthrie 1990, King and Saunders 1984). Early theories, developed during the mid-1800s, implicated humans in the extinctions at the end of the Pleistocene. However, it was not until Martin's (1967) "overkill theory" that or part in these extinctions was given serious consideration. However, a number of confounding factors, including changes in climate, habitat, and ecosystems, must have contributed to the demise of many species.

Another issue confounding the human "overkill theory" is humankind's long association in Eurasia with many of the species that became extinct at the end of the Pleistocene. Consider the wooly mammoth. Why didn't it disappear much earlier than it did in Eurasia? Clearly our ancestors were hunting this species well before human entry into the Americas (Graham and Mead 1987, Grayson 1984, Pielou 1991).

Pielou (1991) hypothesized a natural catastrophe that reduced animal populations and from which they never fully recovered. He further contends that the great wave of extinctions at the end of the Pleistocene has not been convincingly explained (Graham and Mead 1987, Lundelius and others 1983, Semken 1983, Steadman and Martin 1984).

Radiocarbon studies suggest that some extinct North American wildlife species may have survived past 10,000 years BP. Semken (1983) proposed that mastodons, sabercats, sloths, dire wolves, horses, peccaries, and mammoths could have existed as late as 6,000 years BP. Support for these later dates came from the discovery of wooly mammoth remains on Wrangel Island north of the Bering Strait in Russia. These remains were radiocarbon dated to 3,700 years BP. A remarkable aspect of these remains was that these mammoths were only 4 feet tall (Vartanyen 1995).

Changing climate and vegetation during the late glacial and early Holocene caused relocation of wildlife. Species that existed in the Southeast during full and late glacial times adjusted to changing habitat. Elk, moose, and grizzly bear, which had migrated into North America about the same time as humans, moved north (Pielou 1991). Caribou migrated north, out of the Southeast, while species such as spectacled bears, llamas, tapirs, capybaras, and flat-headed peccaries migrated south and are now found only in South America. Jaguars may have migrated out of the Southeast much later. Some early colonists from the Carolinas describe a jaguar, in addition to the mountain lion. The use of the word "tyger" can be found in some early literature in the Southeast (Lefler 1967, Logan 1859), and in Latin America the jaguar is known as "el tigre". Porcupines and fishers may have inhabited parts of the Southeast until the 1600s; opossums and armadillos are now expanding their range northward (Semken 1983). The wooly mammoth, the Columbian mammoth, and American mastodon were declining in size prior to extinction. The Pleistocene black bear was the size of a small grizzly (Kurten 1988). Purdue (1989) reported a similar reduction in size for white-tailed deer during the Holocene. Guthrie (1990) documented a decline in the size of bison and also explains the appearance of the modern American bison from the merging of Bison priscus and Bison occidentalis.

Some animals once thought to have become extinct have been discovered living in small populations. The flat-headed peccary, thought extinct and once a resident of the Southeast, is alive in Paraguay. Also, a species of horse from the Pleistocene believed to be extinct has been found near Tibet. Sightings by natives in the Amazon report a sloth nearly 6 feet tall. Could this be a relative of giant sloth (Pearson 1995)?

The declining size of animals during the Holocene brings up an interesting question. Could the giant armadillo, giant beaver, giant sloth and other species of the Pleistocene have diminished in size to become our modern beaver, armadillo, and sloth?

What caused this dwarfing? Part of the answer may be drastic climatic and vegetation change. Guthrie (1990) postulates an increase in mesic species at the end of the Pleistocene. Mesic species are more toxic to herbivores, and the nutritional level of their foliage is lower. Deterioration of available nutrition would be an important change. Xeric plant species contain higher levels of nutrition, are more palatable, and were more ubiquitous during the drier climate of the Ice Age (Guthrie 1990). The small key deer is the same species as the white-tailed deer but is smaller because of limited nutrition.

Stress may have also been a factor in animal size. Rapidly changing ecosystems combined with human predation may have elevated stress levels in wildlife populations. The combination of changing habitats and human predation probably forced them into less favorable habitat, thereby contributing to nutritional deficits and dwarfing.

The extinction and disappearance of some animals apparently left an impression on the natives of the Southeast. Their stories indicate "things were not always as they are now, and in earlier times many of the large animals and beings of the 'Upper World' came down to live in 'This World.' But 'This World' grew progressively less ideal, and one by one the great animals and beings went back into the 'Upper World'" (Hudson 1976). Perhaps this tale, passed down through generations, relates the extinction process.

As vegetative communities shifted, and changes occurred in wildlife communities at the end of the Pleistocene, humans continued to thrive. Their increasing populations and increasing use of cultural tools and personal ornaments throughout this demanding period testify to their adaptability, ingenuity, and knowledge of the environment.

Early Archaic refers to the southeastern native culture during the early Holocene (Hudson 1976). Migratory hunting and gathering cultures continued into this period. However, there was a greater reliance on deer and smaller game. Spear points declined in size and became side notched. In addition, the number of spear points and tools increased in quantity. Smaller spear points signify a change in hunting technology toward deer and other small game. Archaeologists identify different cultures by the characteristics of spear points. Big Sandy spear points appeared early in the Southeast followed by the Kirk, Palmer, and Stanly spear points (Hudson 1976, Walthall 1980).

There is an apparent change in gathering techniques during this period. Large numbers of stone implements and other tools believed to have been used in the processing of nuts and wild vegetables have been uncovered.

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created: 4-OCT-2002
modified: 08-Dec-2013