Dietary stability inferred from dental mesowear analysis in large ungulates from Rancho La Brea and opportunistic feeding during the late Pleistocene

The Rancho La Brea locality is world famous for asphaltic deposits that trapped and preserved late Pleistocene megafauna over the last 50,000 years. This wealth of paleontological data allows for detailed investigation into paleoecological changes through the last glacial maximum into the Holocene. Here, we used dental mesowear analyses to infer dietary behavior in Bison antiquus, Equus occidentalis, and Camelops hesternus from five deposits (“pits”) spanning the latest Pleistocene: pits 77, 91, 13, 3, and 61/67. Mesowear was compared among pits for each taxon and discriminant function and posterior probability analyses were conducted using a modern dataset to predict dietary categories at Rancho La Brea. Published mesowear scores from late Pleistocene Bison, Equus and Camelops from other localities were included in the discriminant function and posterior probability analyses to assess dietary variability among regions. Mesowear for each taxon did not differ among pits. Posterior probabilities and discriminant function analyses recovered E. occidentalis as a strict grazer with B. antiquus and C. hesternus recovered as mixed feeders. The stability of mesowear scores through the latest Pleistocene suggests average diets of these herbivores did not significantly change at Rancho La Brea. This is in contrast to documented changes in climate and flora proxies of southern California. However, it is unclear whether these proxies are representative of climate and floral changes at Rancho La Brea. Mesowear scores from late Pleistocene populations of Equus, Bison, and Camelops indicate little variability in diet in Equus, modest variability in Bison, and high variability in Camelops. These analyses suggest large ungulates may have been more opportunistic in their feeding strategies and highlights the need for using multiple proxies to clarify dietary behavior of herbivores •Average dental mesowear did not change in Bison, Camelops, and Equus at the Rancho La Brea.•Deciduous fourth premolar mesowear scores are similar to adult cheek teeth, so can be used together.•Published mesowear data plus our dataset suggest opportunistic feeding in Pleistocene ungulates.