Past and present climates : owl pellet composition as an indicator of local climatic change

[摘要] ENGLISH ABSTRACT:During Holocene times a considerable deposit of barn owl pellet material accumulated in theHot Pot Cave at De Hoop Nature Reserve on the southern coast of the Western CapeProvince, South Africa. An excavation of this accumulation has yielded information on barnowl prey species over the past some two millennia.Four distinct layers were excavated and radiocarbon-dated to AD 381, AD 615, AD 991 andAD 1417. The micromammalian cranial contents of these layers were compared to materialfrom 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 certaincranial parameters, (2) micromammal community species composition and (3) communitystructure indices, such as the Shannon-Wiener diversity index, Simpson's diversity index andthe 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 withpossibly more grass than in recent times, while the upper layers represented cool weather witha possible increase in scrub. AD 381 was found to be somewhat dry and mild, AD 615 to bethe wettest level and possibly milder than AD 381, AD 991 to be the coolest of all the levelsand dryest of the ancient levels, AD 1417 to be somewhat cool and probably drier than AD615, but wetter than AD 381, and AD 2000 to be the mildest and dryest of all levels, with theartificial influence of nearby agricultural activities evident.

[发布机构] Stellenbosch University