Browsing by Author "Sponheimer, Matt"

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    The ecological and evolutionary significance of browsing and grazing in savanna ungulates
    (2006) Codron, Daryl; Lee-Thorp, Julia A; Sealy, Judith; Sponheimer, Matt
    Includes bibliographical references (leaves 175-208).
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    Open Access
    Stable carbon isotope reconstruction of ungulate diet changes through the seasonal cycle
    (Southern African Wildlife Management Association, 2007) Codron, Daryl; Lee-Thorp, Julia A; Sponheimer, Matt; Codron, Jacqui
    We analysed stable carbon isotope ratios (ð13C) in faeces of 11 African ungulate species from three South African savanna environments to determine whether this approach is sufficiently sensitive to record short-term seasonal diet changes in browsers (BR), mixed-feeders (IM), and grazers (GR). At monthly intervals, faecal ð13C revealed variations in proportions of C3 (browse) to C4 (grass) biomass consumed that were not detected by broader dry versus wet season comparisons, including subtle diet shifts amongst BR and GR. However, trends in faeces were influenced by changes in C3 and C4 plant isotope composition of up to 3‰. Nonetheless, faeces and plants showed strongly similar patterns of variation through the seasonal cycle, so that small diet shifts can be reliably inferred, provided that the variations in plants are controlled for. Faecal ð13C of BR may be further influenced by consumption of isotopically different plant parts such as foliage versus fruit and flowers, and GR faeces may reflect differential utilization of grass following different photosynthetic sub-pathways. Future studies will need to incorporate data that capture isotopic variations in herbivore food sources, and if this is achieved, the approach may well become adopted as a routine addition to traditional methods for assessing diet, habitat use, and habitat condition.
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    Using carbon isotope data of fossil bovid communities for palaeoenvironmental reconstruction
    (2003) Sponheimer, Matt; Lee-Thorp, Julia A
    Reconstructing palaeoenvironments is a major focus of palaeoanthropological research. While many techniques are now available for exploring past environments, fossil bovids remain amongst the most widely utilized sources of environmental information. Most studies of fossil bovids, however, assume implicitly that bovid ecology is the same now as it was in the distant past. Because such uniformitarianist assumptions are not always valid, we have developed a method to provide palaeoenvironmental information from fossil bovids that requires no ecological assumptions. Here, we show that the percentages of C3 and C4 vegetation-consuming bovids in modern environments generally vary according to the amount of woody vegetation present. Application of this C3 / C4 index to the fossil bovid assemblage at Makapansgat shows that, based on carbon isotope data, the percentage of C3-consuming bovids is high, suggesting a great deal of woody vegetation in this vicinity about 3 million years ago.
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    Utilization of savanna-based resources by Plio-Pleistocene baboons
    (2005) Codron, Daryl; Luyt, Julie; Lee-Thorp, Julia A; Sponheimer, Matt; DeRuiter, Darryl; Codron, Jacqui
    We have determined the tooth enamel carbonate 13C values of five cercopithecoid taxa from the Plio-Pleistocene deposits of Swartkrans Members 1 and 2 and Sterkfontein Member 4. These data were used to determine the relative proportions of C3 and C4 biomass consumed by extinct baboons and contemporary non-human primates. We compared these results with data on modern Papio hamadryas ursinus from different savanna areas in South Africa, as well as with published isotopic data and dietary interpretations based on molar morphology of these taxa. The data reveal little evidence for use of grasses or grass-based foods by modern South African baboons. The fossil papionins Papio hamadryas robinsoni, Papio (Dinopithecus) ingens, and Parapapio spp., however, utilized more savanna-based C4 resources than previously predicted (particularly in the case of P. (D.) ingens). Theropithecus oswaldi had 13C values depicting, as expected, a largely grass-based diet, and we confirm earlier conclusions that this species incorporated a wider range of food items into its diet than do modern T. gelada, as reported in the literature. The colobine monkey, Cercopithecoides williamsi, made extensive use of savanna-.based C4 foods, confirming some degree of terrestrial foraging by the species.