Posts Tagged ‘bison wallows’

Pleistocene Bison Wallows

September 20, 2011

Prairie Violet (Viola pedatifida).  Laura Ingalls’s little toddler sister wandered off and was found in an old “buffalo” wallow overgrown with violets–probably this species.

I admire the clear and concise prose of Laura Ingalls Wilder, author of the famous Little House series for children.  Her stories offer a glimpse of life on the frontier before most of the conveniences we think we can’t live without were even invented.  In one of her books (I believe By the Shores of Silver Lake) she recounts an incident that probably was based on a true event.  (Her stories were a blend of fiction and nonfiction.)  This traumatic adventure occurred when Laura was in her early teens.  They were living in a house in the middle of the short grass prairie in South Dakota.  They were miles from any neighbors.  Laura was helping her mother and father plant small trees to form a windbreak for the house.  While toiling, they didn’t notice Laura’s baby sister, Carrie, had wandered out of sight.  After congratulating themselves for doing such a good job on the hedgerow, they experienced the bad shock of realizing the toddler was missing.  The whole family scattered in different directions searching in panic.  I endured that awful feeling once when my daughter got on the wrong schoolbus on the first day of middle school.  That was the second worst day of my life even though her whereabouts were unknown for only half an hour.  Laura eventually found her sister some distance away sitting in an old bison wallow overgrown with violets.  Carrie was amongst the flowers, pulling them, and saying “sweet, sweet.”

It occurred to me that bison wallowing must have had a significant impact on the environment, altering the habitat so that it favored some species of plants and inhibited others.  However, I didn’t think anybody had ever studied such an esoteric subject.  Happily, I was wrong and found a recent study about bison wallowing published in The American Midland Naturalist.

Photo of a bison wallowing from google images.

Bison create wallows when they repeatedly roll and kick their legs in the same area to rid themselves of parasites, to scratch insect bites, and to give themselves a dust bath which may help stymie ticks, fleas, and flies.  The wallowing forms circular depressions with compacted soil where water is retained longer than on adjacent prairie land.  Some wallows are larger than 2 acres.  There were millions of wallows across North America before the extirpation of the bison.  Most have been plowed under but some still exist and are known as relic wallows.  Cattle do not wallow, and accordingly, habitats created by wallows are limited to the few area where bison still exist.

Scientists studied plant diversity at the Konza Prairie Biological Station in Kansas which is owned by the Nature Conservancy and managed by Kansas State.  They compared the kinds of plant species found in active and inactive wallows and adjacent prairie.  They counted a total of 153 species of plants of which 10 were found only in adjacent prairie and 25 were found only in wallows.  Overall though, they found lower species diversity in active and relic wallows than in adjacent prairie.  Bison rolling, compacted soil, and excess moisture is evidentally intolerable to many species of plants.  Here’s a list of the 5 most common species of plants found in each type of habitat.

Inside Wallows……………Adjacent Prairie

1. Western Ragweed………..Big Bluestem

2. Sedges……………………….Heath Aster

3. Canada Bluegrass………..Sedges

4. Ridgeseed Spurge………..Western Ragweed

5. Hoary verbena……………Scribner’s rosette grass

Plant species diversity is also greater in grazed areas than in ungrazed areas.

During the Pleistocene there must have been tens of thousands of bison wallows, some abandoned, some active across the southeastern coastal plain and into the piedmont.  As I’ve noted in earlier blog entries (See https://markgelbart.wordpress.com/2010/06/11/were-there-three-species-of-bovine-roaming-southeastern-north-america-during-the-late-pleistocene/ and https://markgelbart.wordpress.com/2011/08/01/a-probable-pre-clovis-bison-butcher-site-in-washington/), I suspect there were 2 species of bison living in the region then.  The two species may have hybridized in some areas, and the long-horned bison is probably ancestral to the shorter-horned variety.  Long-horned bison (Bison latifrons) and northern bison (Bison antiquus) fossils have been found throughout the south, and they overlap geographically and temporally.  Long-horned bison may have been more of an open forest species, while its cousin may have preferred more open grassland.  Their wallowing behavior created habitats favorable for some species of plants and detrimental to others.  The common plants found inside and outside of Pleistocene wallows in the southeast undoubtedly differed from the list of plants found in the modern tall grass praire.  The composition of plants in Pleistocene bison wallows will likely remain a mystery.

Reference:

McMillan, Brock; Kent Pfeiffer, and Donald Kaufman

“Vegetation Response to Animal Generated Disturbance (Bison Wallows) in Tall Grass Prairie”

The American Midland Naturalist Jan 2011

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