Observations on Seasonality and Mortality from a Recent Catastrophic Death Assemblage

On 3 November 1991, a group of 150 pronghorn went over a cliff near Green River, Wyoming. This mortality site provides a unique opportunity to examine a number of characteristics of catastrophic death assemblages that may aid in the interpretation of archaeological bonebed sites. In 1993, the mandibles were collected for a study of seasonality and age estimation. Examination of seasonality revealed some variation in estimates by eruption/wear and cementum increments. Six percent of 86 fawn specimens exhibit eruption and wear more advanced than expected for a November third event, and 21% of 28 cementum increment estimates differ from the known November third mortality date by a month or more. These data suggest some degree of error is inherent in seasonality estimates that must be considered when interpreting seasonal distributions. Age estimates by eruption and wear reveal a distribution of pronghorn ages with many more juvenile animals than expected for a known “catastrophic” event. This may be explained by the pattern of seasonal hunting in a modern managed herd, which is likely to be very different than aboriginal hunting patterns. Age estimates by eruption/wear and cementum increment techniques failed to agree within six months in 48% of 29 test cases, with a tendency for cementum ages to be younger in 71% of specimens in which estimates of age differed. In general, the mandible assemblage exhibited more variability than one might expect for a single catastrophic kill event.