ISOTOPIC ANALYSIS OF FOSSIL CORONULID BARNACLES AS A MEANS OF UNDERSTANDING PREHISTORIC WHALE MIGRATION PATTERNS: PRELIMINARY RESULTS

Migration is a defining feature of modern mysticete whale ecology, but it is difficult to know how long migrations have been taking place and whether migration paths have been stable through time. Such knowledge could yield valuable insights into mysticete evolutionary history and may also have implications for crafting conservation strategies. Isotopic analyses of fossil whale barnacles (coronulids) have the potential to help fill this knowledge gap. Killingley (1980) demonstrated that the oxygen isotope profiles of gray whale barnacles (Cryptolepas rhachianecti) could be used to reconstruct the host whale’s migration. We have shown this to also be true in the common humpback whale barnacle, Coronula diadema. However, to date there have been no isotopic analyses of fossil coronulids. Here we present initial results from ongoing analyses of fossil specimens of both Coronula diadema and Cryptolepas rhachianecti. We examine Plio-Pleistocene specimens from the eastern Pacific rim. Preservation of calcite is in most cases excellent, and diagenetic alteration can be diagnosed by textural and trace metal analysis. Oxygen isotope profiles from well-preserved fossils exhibit coherent trends with amplitudes and periods resembling those of modern barnacles, suggesting that prehistoric whales were undertaking migrations similar to those of today. By combining barnacle profiles with local proxies and oceanographic models, it may ultimately be possible to reconstruct whale migration pathways during past climate states.