Niche overlap and competition potential among tigers (Panthera tigris), sabertoothed cats (Homotherium ultimum, Hemimachairodus zwierzyckii) and Merriam's Dog (Megacyon merriami) in the Pleistocene of Java

Abstract

On Java during the Pleistocene, tigers of more than 300kg occurred, but these are restricted to a single Late Pleistocene faunal unit, while Early and Middle Pleistocene tigers possessed body masses comparable to those of historic Javanese and extant Sumatran tigers. However, former studies have excluded carnivores from the Middle Pleistocene site of Sangiran where tigers co-occurred with machairodonts (Hemimachairodus zwierzyckii and Homotherium ultimum) and the large Merriam's Dog (Megacyon merriami). The aim of this study is to test if large tiger individuals occurred already in Early and/or Middle Pleistocene sites in Java and evaluate competition potential among carnivores from Sangiran and its consequences.We calculated body masses and prey mass spectrum for tigers and potential competitors using linear regressions. Niche overlap was then estimated based on the prey mass spectrum after which niche-overlaps were used as indicators for competition potentials. Reconstructed body mass for H. ultimum, H. zwierzyckii, M. merriami are 154kg (comparable to Homotherium from Untermassfeld), 130kg and 52kg, respectively. The niche overlap between tigers and Merriam's Dog is highest (100%) while it is comparatively low (60%) between tigers and H. ultimum. Tigers have not increased body mass before Ngandong faunal level, but competitors like Merriam's Dog seem to have decreased body mass to avoid competition with tigers. The sabertoothed cats on the other hand seem to have been unable to adapt to competition and went extinct.