Abstract
Rock hyrax middens are important palaeoenvironmental archives in southern Africa. Carbon and nitrogen isotope measurements on middens (hyraceum) are key components of climate reconstructions, but their interpretations require refinement. Although d 15 N in hyraceum often correlates with independent proxies for palaeo-aridity, the impacts of dietary and physiological controls on hyraceum d 15 N remain to be resolved. We analyse d 13 C and d 15 N in plant foliage, hyrax faecal pellets and hyraceum from 21 sites across southern Africa. Faeces are generally depleted in 13 C (d 13 C typically < À20‰), suggesting significant browsing. Grazing is rarely dominant and probably occurs only when palatable grass is available. Variability in faecal and foliar d 15 N is large, but foliar d 15 N is positively correlated with faecal d 15 N. The diet-faeces d 15 N offset is uncorrelated with climate (aridity), but is correlated with %N in faeces. Faecal d 15 N is positively correlated with modern hyraceum d 15 N, and the relationships with aridity index for foliar and faecal (body tissue) d 15 N are comparable. These observations implicate diet as a significant control on hyraceum d 15 N and we observe no strong evidence for metabolic controls on hyraceum d 15 N. More data are required to refine these relationships, but these observations are consistent with current palaeoenvironmental interpretations of midden d 15 N and d 13 C.