CLIMATE AND BUNNIES IN THE PLIOCENE OF SOUTHERN IDAHO

The fossil leporid assemblage at Hagerman Fossil Beds National Monument (HAFO), Idaho, is comprised of three extinct species that span about 100 m of exposed Glenns Ferry Formation deposits. During this nearly one million-year interval there is evidence for a pronounced cooling period and subsequent warmth. Response of the leporids to these climatic events is reflected in their diversity, abundance, and dimensions of the lower third premolar (p3). None of the three leporids were present during the coolest interval at HAFO, but all reappear after a long hiatus. This reappearance coincides with a return to warm conditions at HAFO and is additionally marked by a change in the relative abundance of the leporid taxa. All three species exhibit a longer p3 after the hiatus, which suggests that individuals returning to the HAFO area had a larger body size.