Dietary resource partitioning among three coeval proboscidean taxa (Anancus capensis, Mammuthus subplanifrons, Loxodonta cookei) from the South African Early Pliocene locality of Langebaanweg E Quarry

The co-existence of megaherbivores in present-day ecosystems is uncommon. During the Early Pliocene, three large proboscidean taxa (Anancus capensis, Mammuthus subplanifrons and Loxodonta cookei) co-existed in the strongly C₃-dominated Langebaanweg (LBW) environment, on the southwestern coast of South Africa. It is expected that this would have required at least some resource partitioning. To investigate whether/how dietary resources were partitioned, we have measured δ¹³C and δ¹⁸O in tooth enamel from the molars of A. capensis (n = 13), M. subplanifrons (n = 3) and L. cookei (n = 20). δ¹³C values for A. capensis are more tightly clustered and the mean more negative than for L. cookei and M. subplanifrons. Anancus capensis probably favoured shady, wooded parts of the LBW environment, where it mainly browsed. Loxodonta cookei and M. subplanifrons spent more time in open habitats and were dietarily flexible. The preference for browse of A. capensis may have contributed to its extinction, whereas the dietary flexibility of the genus Loxodonta meant it was able to survive to the present. We did not find significant differences in δ¹⁸O values between the three taxa, which suggests that they drank from the same water sources as expected if they were all resident in the LBW palaeoenvironment. Our study shows that the carrying capacity of the C₃- dominated LBW environment was high.