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Tuesday, September 6, 2011

Natural Salt Licks: A Glimpse of the Past

The term “lick” is an old name for places where deer and other wildlife come to lick salt.  Such North American sites are typically fed by saltwater springs.  Michigan originally had licks in places such as Saginaw and the appropriately named Saline, but salt licks gained their greatest fame in Kentucky Territory.  The settlers who pushed across the Appalachians into present day Kentucky and Tennessee in the 1770s found numerous licks there, and prized them for the game they attracted and the salt that could be extracted in iron boiling pots.  Salt was almost as important as game on the frontier because of its use in preserving meat and tanning hides. 

These trans-Appalachian licks also became famous for the bones of animals that had gotten mired in the soft soil or been ambushed by predators.  These included the bones of Ice Age species like mastodons and giant ground sloths.  In fact, Kentucky’s Big Bone Lick is commonly described as the birthplace of American vertebrate paleontology because of its importance in understanding extinct ice age fauna.

Nearly all of the natural salt licks that dotted the Eastern United States in pre-settlement times were changed beyond recognition by salt works and other development in the 1800’s.  However, I had an unusual opportunity to visit an unspoiled salt lick that provides an interesting glimpse of an all-but-vanished part of our natural history.

I never imagined seeing a large lick in an unspoiled condition like Daniel Boone and his contemporaries found them until I was fishing in Northern Ontario a few years ago.  One of my Canadian friends had mentioned visiting a remote salt lick during his days as a trapper.  After he described the lick as a large one that was heavily used by wildlife and scattered with animal bones, three of us quickly decided it would be more interesting to visit this lick than go fishing.

The lick that we found in thick boreal forest in the Lake Nipigon region of Ontario consisted of a large patch of clay with salty water percolating through it to the surface.  We visited the lick in heavy rain when it probably had more standing water than usual, but my photograph still provides a sense of how thoroughly the surface was churned by animal tracks.  The photograph also shows the surrounding forest that contained several well-worn animal trails leading to the lick.

While the rain and sticky clay prevented us from conducting a thorough examination, the lick was roughly square and at least 100 by 100 feet in size.  It did not have any vegetation except some scattered clumps of grass.  The salty water appeared to be seeping up to the surface in numerous locations, and there was no sulfuric smell or other distinctive odor.  We did not find any evidence of other human visitors to the site, and did not see any large animals there on a very stormy day.  However, one of my companions saw two moose using the lick when he re-visited it in better weather a few weeks later.

Most of the tracks that literally covered the lick were moose tracks, and most of the bones scattered around it also appeared to come from moose.  However, we also saw wolf, bear, and caribou tracks.  Bone counts could be misleading because moose bones undoubtedly persist much longer than ones from smaller animals.

It is extremely unlikely that this remote lick has ever been studied, but Ontario scientists did examine some similar-looking but more accessible licks in the same Nipigon region in the 1980’s.  Among their findings, the scientists confirmed that these springs were being pushed up to the surface through fractures in the bedrock by hydrostatic pressure and were very salty.  They also tentatively concluded that this salt was being dissolved out of the bedrock instead of coming from ancient seawater.

Our own historical licks in the U.S. functioned in the same basic way, but probably had a few chemical differences from these northern ones.  They also had the potential to hold more fossils because of the timing of the great glacial retreat.  Southern Michigan has produced a large number of Ice Age fossils like mastodons, mammoths, woodland musk oxen, and giant beaver for hundreds of years after the ice front receded northward.  But none of these animals ever slurped salt from the lick that I visited because Northern Ontario was still covered by the Laurentide ice sheet when they mysteriously disappeared about 11,000 to 12,000 years ago.

1 comment:

  1. Maybe this is why birds like to eat bread.