DEAD DEER TELL SOME TALES: USING MORTALITY PROFILES TO INTERPRET THE CAUSE OF DEATH FOR DROMOMERYX IN RED BASIN, OR

The Red Basin locality in eastern Oregon records a large population of one of the strangest ungulates to ever live: Dromomeryx. Red Basin is dated to the middle-late Miocene (12.5-14.8 Ma). The beginning of this interval saw uncharacteristic warmth and humidity associated with the Mid-Miocene Climatic Optimum; dromomerycid diversity peaked because of habitat spread and increased plant productivity. The latter half of this interval saw cooling and drying, and dromomerycid diversity and abundance declined as their environments were encroached by grasslands. The population at Red Basin has gone understudied for decades. This thesis uses dental wear to determine the relative ages of Dromomeryx individuals from Red Basin. These ages are combined into mortality profiles, which reflect the pressures that may have killed the population. Mortality profiles are often either catastrophic (where individuals die regardless of fitness) or attritional (where only the weakest members die), though other patterns may occur. This research found that the death assemblage of the Dromomeryx population at Red Basin is dominated by prime-age adults. The prime-dominated assemblage is interpreted as indicating a catastrophic flood, where flood waters killed all members and preferentially washed away younger individuals. This research provides insight into the climatic stresses that led to the deaths of these Dromomeryx at Red Basin.