Reconstruction of travel history using coupled δ18O and 87Sr/86Sr measurements of hair

RATIONALE: Oxygen isotope ratios (delta O-18 values) of hair largely reflect features of regional hydrology while strontium isotope ratios (Sr-87/Sr-86) are thought to reflect bedrock geology; combination of both isotope signatures may provide greater capacity for determining provenance and reconstructing travel history of an organism. To test this hypothesis, we compared the O-Sr isotope profiles of hair from domestic horses with known residency histories. METHODS: Tail hairs were collected from a pair of horses pastured together for a period of 16 months, one of which lived in a different location for the 8 months prior. Hair samples were washed with solvents to remove external contaminants prior to sequential sampling for delta O-18 and Sr-87/Sr-86 analysis via TC/EA-IRMS and MC-ICP-MS, respectively. Hair digests were concentrated and analyzed employing low-flow natural aspiration to measure 87Sr/86Sr. RESULTS: Tail hair from the control and transported horses had mean delta O-18 values of 11.25 +/- 1.62% and 10.96 +/- 1.53%, and mean Sr-87/Sr-86 of 0.7101 +/- 0.0006 and 0.7109 +/- 0.0020, respectively. The d delta O-18 and Sr-87/Sr-86 profiles for the control and transported horses were indistinguishable when they were pastured together. The Sr-87/Sr-86 profiles were significantly different during the period that the horses were living apart, while the delta O-18 values were indistinguishable during that period. CONCLUSIONS: By comparing the O-Sr isotope profiles of a control and transported horse, we investigated isotopic signal(s) potentially useful for reconstructing travel histories via high-resolution sequential sampling along single strands of tail hair. Improved analytical capabilities allowed for extremely low Sr abundance samples to be analyzed for Sr-87/Sr-86 and proved capable of resolving a horse's movement between distinct regions. Copyright (C) 2017 John Wiley & Sons, Ltd.