Carbon-Isotope Shifts Recorded in Megafaunal Dietary Niches of C3 and C4 Plants in the Late Pleistocene of South Australia: Correlation with Palaeofloral Reconstructions

Darren R. Gröcke VIEPS Department of Earth Sciences, Monash University, Clayton, VIC 3168, Australia


Stable carbon-isotope analyses (expressed as a 13C / 12C ratio in per mil; d13C”) have been completed on fossilised collagen in megafaunal bones from Cooper Creek, Henschke's Cave, Baldina Creek, Dempsey's Lake and Rocky River in South Australia, Australia. d13C values of collagen can provide information regarding the palaeodietary niche of these animals, for example, C3 (predominantly woody shrubs and trees) and C4 plants (predominantly grasses). The majority of isotope analyses were performed on collagen extracted from Sthenurus sp., Diprotodon sp. and Macropus sp..


Cooper Creek. TL and uranium series dating at Cooper Creek have produced an age range from 132 to 108 ka and AAR dates and abundance of bivalves and gastropods indicate that Lake Eyre was full at ~110 ka (Belperio, 1995). The environment at this time consisted of abundant rivers and lakes supporting dense vegetation with increasing grassland from these water sources. Sthenurus sp. and Macropus sp. indicate diets of C3 plants and a browsing dietary niche, while Diprotodon sp. indicates a mixed dietary niche of
C3 / C4 plants.

Henschke's Cave (36š59'S, 140š45'E). Although no accurate dates have been determined for this locality, an age greater than 100 ka has been estimated (Tedford and Wells, 1990). All herbivores analysed at this locality exhibit a dietary niche of C3 plants, while the omnivore, Bettongia sp. also exhibits a C3 diet, but exhibits an enriched nitrogen-isotope signature (relating to its carnivorous input).

Baldina Creek (33š41'S, 139š04'E). Based on C14 dates and biostratigraphy an approximate age of 30 ka has been assigned to this locality (Williams, 1982). The environment at this time, the onset of the last glacial maximum (LGM), would have primarily consisted of open grasslands with sparse tree vegetation. Sthenurus sp. and Macropus sp. also indicate this change by exhibiting a grazing diet of C4 plants.

Dempsey's Lake (32š28'S, 137š42'E). This locality has been dated to be between 36 - 25 ka (Williams, 1982) . The vegetation was predominantly C4 plants during the LGM, and this is also reflected in the dietary niche of herbivores. However, Macropus sp. and Sthenurus sp. are on the upper limits of the C4 range, indicating that these animals also consumed some C3 plants.

Rocky River (35š55'S, 136š47'E). C14 dates at this locality indicate an age of the lowest section of the pit at 19 ka, however, bones selected for this research were from the uppermost section with an estimated age of 10 - 13 ka (concordant with the uppermost Seton Rock Shelter age of 10 ka). Therefore, Kangaroo Island, at the time of fossil deposition, was separated from the Australian continent by a shallow sea (Gröcke and Bocherens, 1995). The environment was becoming progressively wetter and pollen analysis from Rocky River indicates an open grassland around a swamp with sparse Eucalyptus trees (Hope et al., 1977). Macropus sp. indicates a dietary niche of C4 plants, while Diprotodon sp. and Sthenurus sp. indicate a mixed diet of C3 / C4 plants (Gröcke and Bocherens, 1995).


This type of research approach highlights another
means by which to extract palaeoecological information. The potential for using fossilised collagen in vertebrate remains as indicators of dietary preference can provide an insight into the floral community on a large scale. In addition, correlation with palaeofloral data is significant and suggests that
herbivores shifted their dietary niches with respect to major floristic changes. These shifts in dietary niche are not
indicated by evolutionary changes, such as dental morphology. It is advised that the reconstruction of palaeoecologies in the future requires detailed investigations of sedimentological and spore / pollen records to determine the interrelationships between the flora, fauna and environment.


Belperio, A.P., Geology of South Australia, Volume II, p. 219-280 (1995).

Gröcke, D.R. & Bocherens, H., C. R. Acad. Sci. Series II (1995; in review).

Hope, G.S. et al., J. Biogeogr. 4, 363-385 (1977).

Tedford, R.H. & Wells, R.T., Mem. Qd. Mus. 28, 263-284 (1990).

Williams, D.L.G., Doctorate Thesis, Flinders University, School of Biological Sciences (1982).