In 1995 the skull of a subadult male bison was recovered from the cutbank of Fawn Creek, Lemhi County, Idaho, by a ranger for the Salmon-Challis National Forest. After slowly drying the skull for about a year it was turned over to the Midwest Archeological Center in order to be stabilized and analyzed for clues to the ecology of Late Holocene bison in the Intermountain West.

A number of analytical techniques were applied to the skull in order to understand its age of deposition and ecology.Radiocarbon dating revealed a recent age of 170 ± 70 yr B.P., which calibrates to about the late eighteenth to early nineteenth century. Identification of macrobotanical remains recovered from the infundibulum of the molars, in association with the analysis of pollen and phytoliths extracted from tooth tartar, indicates this bison subsisted on festucoid grasses and other cool-season grasses in an open forest setting. The stable-carbon-isotope analysis is consistent with the plant data—this particular bison lived its life in the mountainous region of the Salmosn River. There is no indication of long distance migrations into the lower valleys of the Lemhi or Snake rivers.

In addition to the physical analyses, an overview of the historic and archeological literature citing bison is presented. The information from these sources indicates that bison were most abundant in the wide grass-covered valleys of the Lemhi River and Snake River. Archeological data indicate that bison may have become more abundant during the Late Holocene, although the statistical correlation is weak.

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