Recent dating of extinct Atlantic gray whale fossils, (Eschrichtius robustus), Georgia Bight and Florida, western Atlantic Ocean.

Ervan G Garrison,Gary S Morgan,Alexander Cherkinsky,Krista Mcgrath,Camilla Speller

doi:10.7717/peerj.6381

Abstract

The Atlantic gray whale (Eschrichtius robustus) presents an interesting case study of climate related dispersal and extinction. While (limited) fossil records confirm its presence in the Atlantic up until the 18th Century, its abundance and distribution within the Eastern and Western basins are still not well understood. The discovery of presumed gray whale fossil remains from the Georgia Bight and the Atlantic coast of Florida, from the mid-1980s to late-2000s, provides a new opportunity to recover additional data regarding their chronology within the Western basin. Here, we apply accelerator mass spectrometry radiocarbon techniques to six fossil whale finds, identifying dates within marine isotope stage 3 (59–24 ka) and the late Holocene, ∼2,000 yr BP. We additionally confirm the taxonomic identification of two fossil bone samples as E. robustus using collagen peptide mass fingerprinting (ZooMS). The obtained dates, when combined with a larger corpus of previously published Atlantic gray whale fossil dates, support the hypothesis for the decline of the Atlantic gray whale in the late Pleistocene and the late Holocene. These new data augment the findings of the Eastern Atlantic Basin and better incorporate the Western Atlantic Basin into a pan-ocean understanding for the species.

Highlights

Recent studies have suggested that changes in species distribution during the Late Pleistocene–Early Holocene transition were caused both by habitat tracking as well as by extirpation of populations outside of isolated habitat refugia (Dalén et al, 2007; De Bruyn et al, 2011; Hofreiter et al, 2004; Hofreiter, 2008; Hofreiter & Stewart, 2009; Stewart, 2009)
We compared the two Florida gray whale skulls to descriptions and photographs of modern skulls of E. robustus (True, 1983, 1904; Barnes & McLeod, 1984) and a late Pliocene skull from Japan referred to Eschrichtius sp. (Ichishima et al, 2006)
Characters the Florida skulls share with E. robustus include: triangular-shaped occipital shield with prominent paired occipital tuberosities; large occipital condyles; concave exoccipitals lateral to occipital condyles; Table 1 Cranial measurements of Quaternary gray whale skulls

Summary

Introduction

Recent studies have suggested that changes in species distribution during the Late Pleistocene–Early Holocene transition were caused both by habitat tracking as well as by extirpation of populations outside of isolated habitat refugia (Dalén et al, 2007; De Bruyn et al, 2011; Hofreiter et al, 2004; Hofreiter, 2008; Hofreiter & Stewart, 2009; Stewart, 2009). The gray whale (Eschrichtius robustus) presents an interesting case study by which to study this type of climate-related dispersal and extinction. Both fossil and historical accounts suggest that the Atlantic gray whale was extinct in the North Atlantic by the mid-1700’s (Mead & Mitchell, 1984; Lindquist, 2000), with both climate and anthropogenic factors implicated in its demise. Due to a paucity of fossil data in both the Eastern and Western basins, the diachronic distribution and abundance of gray whales prior to their disappearance is not well understood

Methods

Results

Discussion

Conclusion