Reconstruction of Travel History Using Coupled delta18O and 87Sr/86Sr Measurements of Hair

This study compared the O-Sr isotope profiles of hair from domestic horses with known residency histories. 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 delta18O and 87Sr/86Sr 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. The study found that tail hair from the control and transported horses had mean δ18O values of 11.25 +/- 1.62 ‰ and 10.96 +/- 1.53 ‰, and mean 87Sr/86Sr of 0.7101 +/- 0.0006 and 0.7109 +/- 0.0020, respectively. The delta18O and 87Sr/86Sr profiles for the control and transported horses were indistinguishable when they were pastured together. The 87Sr/86Sr profiles were significantly different during the period that the horses were living apart, and the delta18O values were indistinguishable during that period. By comparing the O-Sr isotope profiles of a control and transported horse, researchers 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 87Sr/86Sr and proved capable of resolving a horse's movement between distinct regions. (Publisher abstract modified)