Non-exchangeable hydrogen (δ2H) stable isotope ratios in fauna provide enhanced dietary, isotopic niche and home range reconstruction at Aqaba Castle, Jordan

Bone collagen of terrestrial and marine animals (n = 218) recovered from Ottoman period contexts at Aqaba Castle, Jordan (16th-19th centuries CE), were analyzed for delta 13C, delta 15N, and delta 2H isotope ratios. While delta 13C and delta 15N values showed considerable overlap among species in the hyperarid environment, delta 2H values exhibited less overlap, enhancing stable isotopic niche differentiation. In domesticates, delta 2H values show trophic enrichments of +18.4 parts per thousand from herbivores to omnivores (dogs), and +26 parts per thousand to cats which had the highest delta 2H values. Fish delta 2H values show a positive relationship with increasing trophic level but also moderately correlate with body size (r = 0.61, R2 = 0.37). The offset between collagen delta 2H and rainfall (delta 2Hmw) values is smaller for camels (-1.4 parts per thousand), sheep (-4.5 parts per thousand), and goats (+6.8%), than for chickens (-18.5 parts per thousand) and cattle (-27.0 parts per thousand) due to more frequent consumption of 2H-depleted groundwater by the latter species, because of their higher water requirements. Similarities between local precipitation and bone collagen delta 2H values for most terrestrial herbivores suggest the utility of delta 2H values for geographic provenancing. This is explored by overlapping gazelle and chukar collagen delta 2H values over a regional delta 2Hmw isoscape, tentatively suggesting these species inhabited the water-stressed highland environments surrounding Aqaba Castle. This study demonstrates the advantages of incorporating bone collagen delta 2H values alongside delta 13C and delta 15N values as a useful environmental proxy, enhancing interpretations of animal dietary behaviour, trophic levels, water sources, and wild animal home ranges.