The potential of palynology in fossil bat-dung from Arnhem Cave, Namibia

Abstract

Modern and fossil pollen grains extracted from bat guano in Arnhem Cave are evaluated for their potential as a palynological archive and the possible influence of insectivorous bat behaviour on the pollen contents of their dung. Four out of seven fossil guano samples from this cave were productive. The inconsistent preservation of pollen in bat guano layers may be due to deterioration through various mechanisms, including combustion. The samples that did contain pollen support previous conclusions, derived from pollen in spring deposits, about Holocene palaeoenvironmental changes in central Namibia. Two samples of modern bat dung yielded pollen spectra with a greater proportion of woody plant pollen than grass pollen in comparison with the fossil guano material, indicating denser tree cover than in the past, which may be due to the possible effect of modern farming practices. Differences in the pollen composition in dung of different bat species foraging in a relatively homogenous African savanna suggest that the behaviour of likely bat populations should be accounted for when using bat guano as a palynology source for environmental reconstruction.

Keywords:

• pollen
• bat guano
• cave sediments
• Holocene
• African savannah

ACKNOWLEDGEMENTS

Research in Arnhem Cave was facilitated by Jannie and Elmarie Bekker and initiated by John Irish.

DISCLOSURE STATEMENT

Any opinions, findings and conclusions are those of the authors and the National Research Foundation does not accept any liability in regard thereto.

Additional information

Funding

The Director of the Geological Survey of Namibia (R. McG. Miller) funded the radiocarbon dating by the late Dr J.C. Vogel, then Director of the Quaternary Dating Research Unit, CSIR, in Pretoria. The National Research Foundation funded the palynological research.