Sample collection:
Fossil seal samples were collected during the austral summers of 2005/06, 2006/07, 2012/13, and 2013/14 in Antarctica in the Dry Valleys and along the Victoria Land Coast (especially Inexpressible Island on Terra Nova Bay), Antarctica. Since this region experiences unusually dry and cold conditions, carcasses and bones are well-preserved, potentially for several thousand years, and therefore have unchanged isotopic compositions in most cases. The sampled species were crabeater, Weddell, leopard, and southern elephant seals. Latitude and longitude of each specimen was recorded and several photographs were taken of each specimen. Bone and carcass weathering states were determined. Several samples were gathered from the specimens. Most commonly, bone was collected, followed by skin and fur; nails, teeth, and whiskers were not frequently available for sampling, but taken when possible. Samples were collected with ethanol-cleaned tools, stored in Whirl-Pak bags, and refrigerated (~4 °C) when we returned from the field.

Species identification and radiocarbon analysis:
When possible, species identification of each specimen was conducted in the field via examination of teeth or bones with features unique to the four pinniped species. Additionally, the team at the University of Durham in the United Kingdom extracted and analyzed DNA from many specimens (described in Fossil Seal Bulk Isotopes 14C) to confirm or establish the species identification. Full details on radiocarbon dating are supplied in that sheet as well.

Most skeletal measurement were made in the field with a steel tape measure or calipers (for tooth row length). In many cases, parts of bones were obscured by tissue, so measurements are approximate. Refer to the Bone Measurment Guide (PDF).