On the Holocene History of Some Northern Great Basin Lagomorphs

Abstract

Analysis of vertebrate faunas from archaeological sites in south-central Oregon's Fort Rock Basin supports the hypothesis that the common early Holocene jackrabbit in the northern Great Basin was Lepus townsendii , and that L. californicus did not become abundant in this area until middle Holocene times. The current range expansion of L. californicus at the expense of L. townsendii in the northern Great Basin and adjacent Plateau may, in part, represent the continuation of a process that began several thousand years ago. These faunas also document the presence of pikas ( Ochotona princeps ) in the Fort Rock Basin prior to, but not after, 7,000 years B.P. Pikas are absent from the area today; their disappearance here may have been due to the eruption of Mt. Mazama at, or just before, an episode of climatic change. These data support the argument that the distribution of boreal mammals on mountainous islands within the Great Basin can be accounted for by initial colonization followed by extinctions of geographically intermediate populations.