Size variation in the Cape dune molerat (Bathyergus suillus) and late Quaternary climatic change in the southwestern Cape Province, South Africa

Within their historic range at the southwestern tip of Africa, Cape dune molerats (Bathyergus suillus) tend to be significantly larger in areas of higher rainfall. They also tend to be large in late Quaternary fossil samples associated with independent evidence for relatively moist climate and small in samples associated with evidence for relatively dry conditions. Together with sedimentologic/geomorphic and other faunal observations, fluctuations in fossil dune molerat size imply that the regional climate was very moist during an early late Quaternary interval corresponding to marine isotope stage 4 (74,000 to 59,000 yr B.P.) or perhaps to substage 5b or 5d (centered on 110,000 and 90,000 yr B.P., respectively.) It was comparably moist again from roughly 14,000 to 8,000 yr B.P., somewhat drier than at present from about 8000 until 4000 yr B.P., and mainly near the modern average after 4000 yr B.P. Together, the modern and fossil data suggest that dune molerat size is a reliable index of past precipitation, but it may not be useful for revealing extremely arid conditions because these seem to be associated with depositional/occupational gaps in most local paleontological/archeological sites.