Bring your animals: provenance and diet from the Iron Age mass animal sacrifice at Casas del Turuñuelo (Guareña, Spain)

• A new strontium (87Sr/86Sr) isoscape of the Iberian Peninsula is provided with an open-access R script. • supplementary material Strontium data reveal diverse geographic origins and complex mobility patterns for equids at Casas del Turuñuelo. • Carbon and oxygen isotopes show horses received fodder, while caprines relied on local grazing resources. • Multi-isotopic analysis offers new insights into Tartessian livestock management and animal husbandry (5th c. BCE). • Findings illuminate the scale and cultural significance of mass animal sacrifice in Iron Age Iberia. The excavations at the Tartessian monumental building of Casas del Turuñuelo (Guareña, Spain) uncovered the remains of a special event that took place before the intentional closure and burial of the building under an earth mound at the end of the 5th century BCE. During this event, a banquet was held inside the building, and at least 52 animals – mainly equids – were sacrificed in different stages in the courtyard. Sequential multi-isotopic analyses ( 87 Sr/ 86 Sr, δ 13 C, and δ 18 O) from enamel carbonate from a total of 23 teeth were analysed to assess the geographic origin and potential mobility patterns of 4 cattle, 3 sheep and 12 equid individuals recovered both from the courtyard and from the interior of the building. The strontium results reveal a diversity of origins and movement behaviours: some individuals showed intra-tooth isotopic variability, while others display very stable 87 Sr/ 86 Sr ratios throughout enamel mineralisation. Carbon and oxygen data suggest that horses were supplemented with fodder whenever necessary and had access to a stable water source to maximise their well-being during growth time. In contrast, caprines (sheep/goats) mainly relied on locally available pastures and water. This constitutes the most comprehensive study of equid provenance and diet in the south-western Iberia to date, and provides the first isotopic evidence for caprine mobility in Spanish Extremadura. Finally, the results provide new insights into animal management strategies and the cultural significance of Tartessian sacrificial rites.