Browsing by Author "Avery, Margaret"

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    Avian fauna, palaeoenvironments and palaeoecology in the late quaternary of the Western and Southern Cape, South Africa
    (1990) Avery, Graham; Parkington, John; Van der Merwe, Nick; Avery, Margaret
    Avian remains in coastal archaeological samples from Eland's Bay Cave, Die Kelders Cave 1 and Nelson Bay Cave in the Cape Province, South Africa, cover the periods between 80 000 and 40 000 B.P. and 18 000 and 300 B.P. Results of modern comparative surveys indicate that beached birds provide a predictable food supply. Kolmogorov-Smirnov two-sample nonparametric tests confirmed the close resemblance between the relative proportions of seabirds in archaeological and beached assemblages and earlier assumptions that the composition of seabird samples in archaeological sites could not otherwise have been achieved. It is shown that this simple but effective practice has a history going well into the Middle Stone Age. Kolmogorov-Smirnov tests for differences between the relative proportions of skeletal elements of Cape cormorants preserved in archaeological and modern jackal accumulations provided a useful means of drawing attention to possible activity of jackals and/or domesticated dogs. Recognition that diagenesis in some earlier samples may mimic the characteristics of modern jackal samples has established the need to extend the comparison of skeletal elements to additional species and to study the relative durability of avian skeletal elements. Similar comparison with the proportions of modern mammalian and avian predator prey species and size (mass) categories provided no indication that black or martial eagles might have contributed to the samples. Similarly, present knowledge of Cape eagle owls argues against their being likely inhabitants of caves suitable for occupation by people. It is concluded that people were the primary accumulators of the assemblages studied and that the role of small food items in prehistoric subsistence can be addressed with greater confidence. Correspondence analysis was used to determine the existence of seasonality in the modern beached seabird samples. The profiles of the archaeological samples are plotted in relation to months in which they were most likely to have been collected. Seasonal evidence from species not subjected to the correspondence analysis supported these results. The results obtained closely supported the hypothesis for seasonal exploitation of the coast. It was also possible to indicate that visits were probably of short duration and that their timing varied. Exploitation of seabirds did not coincide with the period of maximum availability of beached birds. Comparison of the avian evidence with that from seals, Cape dune mole rats and steenbok/grysbok suggested that small food items comprised part of a seasonal strategy that made maximum use of a range of seasonal resources. Evidence for significant local environmental change in addition to, and in support of, existing information has been obtained. Fluctuations in marine, freshwater and terrestrial birds at Eland's Bay Cave have been related to evidence for changes in terminal Pleistocene and Holocene sea levels and the position of the coast, and in the morphology of Verlorenvlei. At Die Kelders Cave 1 between 80 000 and 40 000 B.P., previously drier conditions were ameliorating and mixed scrub and grass and freshwater existed on the coastal foreland in the vicinity of the cave. Fluctuations in frequencies of seabirds indicate that the sea level rose slightly and then receded during the period of deposition. At Nelson Bay Cave samples indicate the approach of the coast after the Last Glacial Maximum, the disappearance of grassland and its replacement by scrub and bush as significant elements of the vegetation. Freshwater birds did not respond as expected, however, indicating that their interpretation at Nelson Bay Cave is complex and not consistent with evidence for wetter or drier conditions. A possible link has been shown to exist between fluctuations of albatrosses, petrels and shearwaters at Nelson Bay Cave and the intensity of wind patterns which are related to oceanic and atmospheric circulation. Further investigation should establish whether seabirds would provide an index of climatic conditions without support from other sources.
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    A taphonomic investigation of the agency of microfaunal accumulation at Elands Bay Cave
    (1998) Matthews, Thalassa; Parkington, John; Avery, Margaret
    Up until the present, analyses of micromammal assemblages in South Africa have been based upon the premise that the agent responsible for the accumulation of these assemblages was the Barn owl. These micromammal assemblages were used to make extrapolations of past changes in vegetation and climate. It was assumed that the agent of accumulation, the Barn owl, remained constant. This thesis used taphonomy to analyse the micromammal bones from Elands Bay Cave in order to question the traditional assumption of the Barn owl as predator arid to ascertain which predator/s had been responsible for the accumulation of the microfaunal assemblages. The methods used to identify the accumulator of the microfaunal assemblages from Elands Bay Cave were based on those used by Andrews (1990a) in his investigation of the bone contents of pellets and scats of several species of owl, diurnal birds of prey and small carnivores. The results from Andrew's(1990a) analyses provided comparative information on breakage patterns of the cranial and postcranial bones and on the acid etching (produced during digestion) on micromammal bones and teeth, caused by the various species of predator. Information on the habits of various predators was collected. This information was used in combination with the results obtained from the analysis of the breakage patterns of the mandibles, maxillae and long bones, and from the acid etching on the incisors, in order to ascertain the agent of accumulation of the micromammal bones from Elands Bay Cave. The breakage patterns of the long bones and the acid etching on the incisors of the micromammals indicated that a variety of predators had contributed to the micromammal assemblages in the Holocene packages of the site. The Terminal Pleistocene packages appeared to have been deposited by a Bamowl but there was some circumstantial evidence that people may have also been responsible for the accumulation of some of the micromarnmal remains in these packages. The results from this thesis indicate that taphonomy should be used to ascertain the predator of micromammal assemblages prior to using the assemblages to trace palaeoenvironmental change. The use of taphonomy at Elands Bay Cave highlighted some of the problems that may arise when dealing with small samples and also raised the issue of the affect that the period of deposition of an archaeological assemblage could have on the micromammal population represented. This thesis found evidence that contradicts the traditional assumption, usually made in the analysis of micromammal assemblages in South Africa, that short-term fluctuations in rodent communities may be safely ignored during analysis.