Department of Animal Sciences

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Browsing Department of Animal Sciences by browse.metadata.advisor "Avery, D. M."

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    Past and present climates : owl pellet composition as an indicator of local climatic change
    (Stellenbosch : Stellenbosch University, 2001-03) Van Niekerk, Christiaan Hermanus; Nel, J. A. J.; Avery, D. M.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: During Holocene times a considerable deposit of barn owl pellet material accumulated in the Hot Pot Cave at De Hoop Nature Reserve on the southern coast of the Western Cape Province, South Africa. An excavation of this accumulation has yielded information on barn owl prey species over the past some two millennia. Four distinct layers were excavated and radiocarbon-dated to AD 381, AD 615, AD 991 and AD 1417. The micromammalian cranial contents of these layers were compared to material from two pellet collections that represent modem bam owl predation at De Hoop (AD 2000). Comparisons were made from three perspectives: (1) physical size measurements of certain cranial parameters, (2) micromammal community species composition and (3) community structure indices, such as the Shannon-Wiener diversity index, Simpson's diversity index and the species equitability index. By extrapolating from known ecological distribution information of the relevant prey species, these data were used to recreate the local climate at the time of the accumulation of the layers. The results were compared to other palaeoclimate models for the region as a test of validity. It was found that the lower two layers of the sequence represented mild conditions with possibly more grass than in recent times, while the upper layers represented cool weather with a possible increase in scrub. AD 381 was found to be somewhat dry and mild, AD 615 to be the wettest level and possibly milder than AD 381, AD 991 to be the coolest of all the levels and dryest of the ancient levels, AD 1417 to be somewhat cool and probably drier than AD 615, but wetter than AD 381, and AD 2000 to be the mildest and dryest of all levels, with the artificial influence of nearby agricultural activities evident.