Sea turtle shells in the Netherlands: Zooarchaeology by mass spectrometry and stable isotope analysis identify species and provenance

Sea turtles (Cheloniidae) are extremely rare in the Northern European archaeological record; however, sporadic finds have occurred. Here we used bioarchaeological tools to investigate two archaeological sea turtle specimens found in the Netherlands. The aim of this study is to investigate whether these represented stranded or imported specimens. The first specimen was excavated in Schagen, a city in the north-west of the country, and has an approximate age predating AD 1500. The second specimen was excavated in Leeuwarden, Friesland, from an early-modern deposit spanning AD 1650–1850. We employed a combination of zooarchaeology by mass spectrometry (ZooMS) and δ13C and δ15N stable isotope analysis. ZooMS analysis identified the Schagen and Leeuwarden specimens as a loggerhead turtle (Caretta caretta) and a green turtle (Chelonia mydas), respectively. Isotope provenancing based on modern samples from different global regions indicated the Leeuwarden specimen was most likely imported during a period when sea turtle soup, a high-status meal, was at the height of popularity. This approach demonstrates how bioarchaeological methods, combined with ecological insights, can shed light into the history of sea turtle occurrences and trade.