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 300 kg 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. The aim of this study is to test if competition for prey with other hypercarnivorous taxa such as sabertoothed cats and the large Merriam's Dog was the driver for the increase in body mass of tigers. 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 Homotherium ultimum, Hemimachairodus zwierzyckii, Megacyon merriami are 154 kg (comparable to Homotherium from Untermassfeld), 130 kg and 52 kg, respectively. The niche overlap between tigers and Merriam's Dog is highest (100%) while it is comparatively low (60 %) between tigers and Homotherium ultimum. In order to reduce competition, tigers seem to have increased body mass to avoid competition especially with Merriam's Dog whereas Merriam's Dog on its turn seems to have decreased body mass to avoid competition with tigers. The sabertoothed cats on the other hand seem to have been unable to adapt and went extinct.