Relative Abundance of Bison, Elk, and Pronghorn on the Southern Plains, 1806-1857

Abstract

We searched diaries of travels over the Southern Plains from 1806-1857 for reports ofbison, elk, and pronghorn. From these accounts we obtained indexes of abundance by dividing the number of days in which the animals were observed by the total number of days spent by the expeditions in each of the three prairie biomes. Organizedby historical period and biome type, results show that populations of these ungulates were unstable even during the first half of the nineteenth century. The most stable populations throughout the survey period were bison on mixed-grass prairies. Bison and elk disappeared from tall-grass regions by 1833. Bison were exceptionally numerous on short-grass prairies prior to 1821 but dropped off sharply thereafter. Elk abundance was highest on tall-grass prairies during the earliest historical periods. Pronghorn were most abundant on short-grass prairies during 1806-1820 and again during the 1850s, and most abundant on mixed-grass prairies between those periods. Human influences were likely responsible for the paucity of bison on tall-grass prairies. The persistence of all three species on mixed-grass prairies was influenced by that biome’s distance from centers of human populations encroaching from both east and west.