BIOGEOGRAPHY IN THE ANCIENT OCEANS: INITIAL INSIGHT FROM PREHISTORIC WHALE MIGRATIONS

Oxygen isotope profiles collected from modern-day coronulid barnacles reflect the migratory paths of their mysticete whale hosts. Because coronulids have a fossil record that extends to the late Pliocene, they offer a means by which to assess the migratory behaviors of prehistoric mysticetes. We analyzed fossil coronulids from three different Pleistocene-aged deposits. Fossil coronulids from two southern California sites suggest that ancient populations of both the gray whale and humpback whale lineages were undertaking migrations of similar extent to modern-day populations that frequent these areas. Analysis of fossil coronulids from the Burica Peninsula of Panama suggest that ancient humpback lineage whales were migrating to the region, and also imply that some aspects of biogeographic structure have been stable over very long timescales: modern humpbacks that breed in the Gulf of Panama migrate to the Southern Ocean, the Gulf of Alaska, or the California Current system, and our Pleistocene-aged fossil coronulids exhibit highly variable oxygen isotope profiles. Because coronulid shell oxygen isotope ratios are influenced by both the temperature and the isotopic composition of seawater, reconstructing plausible ancient migration routes will necessitate integrating proxy constraints for these variables in the Pleistocene into oceanographic models. Doing so may reveal how different climate states have impacted both mysticete whales and the oceanic food webs on which they rely.