Evidence for environmental conditions during the last 20 000 years in Southern Africa from C-13 in fossil hyrax dung

C-13/C-12 ratios in plants depend on factors Like temperature, evaporation or seasonal moisture distribution. Fluctuations of C-13/C-12 in Procavia ca pensis (hyrax) dung samples from different vegetation zones and various age s over the last 20 000 years indicate variations in the amounts of C4 and C AM, or C3 plants consumed by these herbivores. Potentially they also indica te vegetation changes that may have occurred. C-13/C-12 values for a series of hyrax middens of Late Pleistocene/Holocene age, from a variety of biome s across Southern Africa, show that hyraxes favour mainly C3 plants in thei r diets but they do incorporate CAM or C4 plants under certain circumstance s. In the eastern mountainous summer-rain area around Clarens with C3 woodl and and unpalatable "sour" grassland consisting mainly of C4 grasses and fe wer of the C3 type, hyraxes seem to avoid at least the C4 component of gras s and rely mainly on leaves of the woody plants. Isotopic data for hyrax du ng in the western Cape Cederberg region indicate diets composed almost excl usively of C3 plants during the last 20 000 years. Slight shifts towards mo re enriched values occur, e.g., around 420 and 2100 years ago, which may in dicate slight increase in CAM or C4 plants. Interestingly no enrichment occ urs during the Last Glacial Maximum when a shortage of atmospheric CO, may have favoured C4 plants. During the late Holocene some CAM and/or C4-plant ingestion by hyraxes is suggested in the dry western and southern areas whi ch receive more summer rains, probably reflecting the availability of some palatable (or "sweet") summer grasses. Although slight, a comparable patter n of isotope change is observed in three areas viz., the Cederberg, the Kar oo and the Namib Desert, suggesting that plant cover is responding to regio nal climate mechanism ca. 2100 years BP. This does not necessarily imply si milar seasonal rainfall shifts over the whole of this wide area, (C) 2000 E lsevier Science B.V. All rights reserved.