The Holocene history of bighorn sheep (Ovis canadensis) in eastern Washington state, northwestern USA

Historical data are incomplete regarding the presence/absence and distribution of bighorn sheep (Ovis canadensis) in eastern Washington State. Palaeozoological (archaeological and palaeontological) data indicate bighorn were present in many areas there during most of the last 10 000 years. Bighorn occupied the xeric shrub-steppe habitats of the Channeled Scablands, likely because the Scablands provided the steep escape terrain bighorn prefer. The relative abundance of bighorn is greatest during climatically dry intervals and low during a moist period. Bighorn remains tend to increase in relative abundance over the last 6000 years. Bighorn were present in eastern Washington in the nineteenth century, but were largely locally extirpated by the twentieth century. A collection of prehistoric bighorn astragali that likely includes specimens spanning the terminal Pleistocene and the entire Holocene consists of specimens that are, with one exception, the same size as a collection of modem bighorn astragali from Wyoming. The single exceptionally large specimen falls in the middle of the size range of specimens from the late Pleistocene of northern Wyoming, suggesting that Washington's prehistoric bighorn, like those from other areas, were larger than modern bighorn.