Life history of middle Pleistocene endemic ruminants (Axis lydekkeri and Duboisia santeng) of Java (Indonesia)

Shifts in life-history traits may accompany other evolutionary changes in mammals during climate oscillations or long-term isolation or in response to predator pressure among other factors. Here, we studied two extinct endemic ruminant species from Java (Indonesia), the deer Axis lydekkeri and the antelope Duboisia santeng. These two species are part of the Middle Pleistocene Stegodon-Homo erectus fauna. Mortality profiles based on their fossil remains were reconstructed to address the life-history strategies of these two species. Individual age was estimated from mandibular and isolated teeth using the Quadratic Crown Height Method. We found that the mortality profiles for both species are L-shaped with both a high juvenile mortality but also a substantial survival after senescence. These results correspond with what is known thus far about life-history traits of medium-sized continental ungulates with perhaps an indication of a shift toward a slower life, with maximum survivability around 70–80% of potential ecological longevity. We further discuss differences in the shapes of the profiles of the two ruminants in light of the presence of Homo erectus hunter-gatherers.