Tracing the ecophysiology of ungulates and predator–prey relationships in an early Pleistocene large mammal community

Abstract

Research into the reconstruction of ancient communities in terms of dietary regimes, habitat preferences and ecological interactions of species has focused predominantly on biogeochemistry or ecomorphology alone and not in combination. The Venta Micena site (Orce, Guadix–Baza basin, SE Spain) has an early Pleistocene vertebrate assemblage with exceptional biomolecular preservation. Collagen was successfully extracted from 77 bone samples of 18 species of large mammals, which allowed analyses of carbon- and nitrogen-isotopes. δ13C, δ15N and δ18O ratios combined with ecomorphological indexes provide interesting clues on the autecology and palaeophysiology of extinct species, which help in deciphering aspects of community trophic structure and predator–prey interactions. Specifically, morphometric ratios (e.g., hypsodonty index and relative length of the lower premolar tooth row; [Palmqvist, P., Gröcke, D.R., Arribas, A., Fariña, R. 2003. Paleoecological reconstruction of a lower Pleistocene large mammals community using biogeochemical (δ13C, δ15N, δ18O, Sr:Zn) and ecomorphological approaches. Paleobiology 29, 204–228.]) allow classifying the ungulates among grazers (Equus altidens, Bison sp., Praeovibos sp., Hemitragus albus, Hippopotamus antiquus, and Mammuthus meridionalis), mized-feeders (Soergelia minor and Pseudodama sp.) and browsers (Stephanorhinus sp. and Praemegaceros cf. verticornis). However, δ13C values reveal that these ungulates consumed exclusively C3 plants and significant differences in isotopic values between perissodactyls (monogastric, hindgut fermenters) and ruminants (foregut fermenters) must reflect physiological differences related to their rates of methane production and digestive efficiency. δ18O ratios allow the interpretation of the dietary water source of these species, suggesting that fallow deer Pseudodama sp., goat H. albus and ovibovine S. minor obtained a significant fraction of their metabolic water from the vegetation consumed. Carnivore species have higher δ15N values than herbivores, which records the isotopic enrichment expected with an increase in trophic level. However, the unexpectedly high δ15N values of hippo H. antiquus and muskoxen Praeovibos sp. suggest that these ungulates predominantly consumed aquatic plants and lichens, respectively. Inferences on predator–prey relationships within this ancient community, derived from the dual linear mixing model, indicate resource partitioning among sympatric predators, suggesting that sabre-tooth Megantereon whitei and jaguar Panthera cf. gombaszoegensis were ambushers of forest environments while sabre-tooth Homotherium latidens and wild dog Lycaon lycaonoides were coursing predators in open habitat. The giant, short-faced hyena Pachycrocuta brevirostris scavenged the prey of these hypercarnivores.