Dr. Josh Miller
University of Cincinnati

Topic: Caribou migrations and mammoth extinctions: Contributions from Arctic taphonomy

Academic host: Carl Simpson

Abstract: Bones lying on today’s landscapes provide opportunities to reconstruct historical states of modern ecosystems and offer insight into the biological data captured in fossil records. Accumulations of shed caribou antlers (Rangifer tarandus) can dramatically expand the temporal scope with which we evaluate seasonal landscape use of herds. Today, maintaining access to spring calving grounds and associated migration routes are top conservation and management priorities. But how long have herds used particular calving grounds and how representative are modern patterns of seasonal landscape use to periods that pre-date recent climatic perturbations and increased anthropogenic stresses? I address these questions for the Porcupine Caribou Herd, which uses the Coastal Plain of the Arctic National Wildlife Refuge (AK) as a calving ground. While male caribou shed their antlers after they mate, pregnant females maintain their antlers until shedding them within days of giving birth (in the spring). Using standardized antler surveys across the Coastal Plain, I found that female antlers are highly abundant on the tundra (~1,000/km2) and the majority come from caribou that lived prior to the initiation of modern, standardized biomonitoring studies (early 1980s). This includes antler that were shed thousands of years ago, illustrating that caribou have calved on the Coastal Plain across at least several millennia. The millennial-scale persistence of antlers in the Arctic also has implications for using DNA recovered from sediments (environmental DNA; eDNA) to understand the extinctions of Pleistocene species. For example, mammoth eDNA recovered from Holocene sediments has recently been used as evidence that this species, contrary to the fossil record, survived on mainland Alaska and Siberia until just a few thousand years ago. By evaluating bone persistence globally, I show that rather than indicating survival, mammoth eDNA in Holocene sediments likely came from decaying Pleistocene individuals.