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

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

Multi-scale agent-based simulation of long-term dispersal processes : challenges in modeling hominin biogeography and expansion

The Out-of-Africa-Theory, as a model of the early migration of anatomically modern humans, describes Africa as geographical source of dispersal processes to Eurasia. However, there is no scientific consensus on the reason or the exact route of the migration. In this paper key challenges for modeling hominin biogeography and expansion using agent-based approaches are being proposed

Diversity, population structure and palaeoecology of the Pleistocene large cervids from the Padang Highlands, Sumatra

This chapter deals with the dentognathic remains of the Late Pleistocene large cervids from the Padang Highlands caves in Sumatra. We used linear and geometric morphometric techniques to investigate variation, taxonomic position and body size trends in a dataset of upper and lower molars. Dental mesowear was used to assess dietary preference in a subsample. The results suggest the Padang Highlands cervids belonged to multiple populations of an early stock of Rusa deer the size of sambar (Rusa unicolor), but morphologically reminiscent of Javan rusa (Rusa timorensis). The Rusa sp. of Sumatra was reconstructed as a mixed feeder with an increase in the grazing component with age

Dietary strategies of Pleistocene Pongo sp. and Homo erectus on Java (Indonesia)

During the Early to Middle Pleistocene, Java was inhabited by hominid taxa of great diversity. However, their seasonal dietary strategies have never been explored. We undertook geochemical analyses of orangutan (Pongo sp.), Homo erectus and other mammalian Pleistocene teeth from Sangiran. We reconstructed past dietary strategies at subweekly resolution and inferred seasonal ecological patterns. Histologically controlled spatially resolved elemental analyses by laser-based plasma mass spectrometry confirmed the preservation of authentic biogenic signals despite the effect of spatially restricted diagenetic overprint. The Sr/Ca record of faunal remains is in line with expected trophic positions, contextualizing fossil hominid diet. Pongo sp. displays marked seasonal cycles with ~3 month-long strongly elevated Sr/Ca peaks, reflecting contrasting plant food consumption presumably during the monsoon season, while lower Sr/Ca ratios suggest different food availability during the dry season. In contrast, omnivorous H. erectus shows low and less accentuated intra-annual Sr/Ca variability compared to Pongo sp., with δ13C data of one individual indicating a dietary shift from C4 to a mix of C3 and C4 plants. Our data suggest that H. erectus on Java was maximizing the resources available in more open mosaic habitats and was less dependent on variations in seasonal resource availability. While still influenced by seasonal food availability, we infer that H. erectus was affected to a lesser degree than Pongo sp., which inhabited monsoonal rain forests on Java. We suggest that H. erectus maintained a greater degree of nutritional independence by exploiting the regional diversity of food resources across the seasons

Écologie alimentaire de <i>Muntiacus muntjak</i> au Pléistocène Terminal dans les Highlands de Padang (Sumatra)

La collection Dubois comporte environ 1000 dents fossiles isolées de Muntiacus muntjak, en provenance des Highlands de Padang à Sumatra. La majorité ont été récoltées dans trois grottes, Lida Ajer, Sibrambang et Jambu. Lida Ajer est la seule grotte dont on connaisse la localisation exacte, la géologie ainsi que l’âge des dépôts fossilifères. En utilisant la méthode de denture « Mesowear », on tente de trouver des différences dans le signal alimentaire de Muntiacus muntjak, et ainsi dans les paléoenvironnements des trois grottes. Muntiacus muntjak ne se distingue de façon significative d’aucun individu issu des autres grottes dans la composition de sa nourriture, se révélant ainsi un mangeur de nourriture mixte. Les échantillons de Lida Ajer et Sibrambang illustrent l’augmentation de composants d’alimentation mixte, qui pourrait résulter d’un plus net caractère saisonnier de la nourriture.The Dubois Collectie comprises around 1000 isolated fossil teeth of Muntiacus muntjak from the Padang Highlands in Sumatra. The majority were retrieved from one of the three fossil cave sites Lida Ajer, Sibrambang or Jambu. Lida Ajer is the only cave, for which exact location, geology as well as the age of the fossiliferous deposits are known. Using the mesowear method, we searched for differences in the dietary signal of Muntiacus muntjak and thus in the paleoenvironments of the three caves. Muntiacus muntjak from either one of the caves does not differ significantly in the composition of its diet, showing a mixed feeder signal. The samples of Lida Ajer and Sibrambang illustrate an increase of the mixed feeding component, which could be the result of higher seasonality.</p

Multi-scale agent-based simulation of long-term dispersal processes : challenges in modeling hominin biogeography and expansion

The Out-of-Africa-Theory, as a model of the early migration of anatomically modern humans, describes Africa as geographical source of dispersal processes to Eurasia. However, there is no scientific consensus on the reason or the exact route of the migration. In this paper key challenges for modeling hominin biogeography and expansion using agent-based approaches are being proposed

Discovering the opposite shore: how did hominins cross sea straits?

Understanding hominin expansions requires the comprehension of movement processes at different scales. In many models of hominin expansion these processes are viewed as being determined by large-scale effects, such as changes in climate and vegetation spanning continents and thousands or even millions of years. However, these large-scale patterns of expansions also need to be considered as possibly resulting from the accumulation of small-scale decisions of individual hominins. Moving on a continental scale may for instance involve crossing a water barrier. We present a generalized agent-based model for simulating the crossing of a water barrier where the agents represent the hominin individuals. The model can be configured to represent a variety of movement modes across water. Here, we compare four different behavioral scenarios in conjunction with a set of water barrier configurations, in which agents move in water by either paddling, drifting, swimming or rafting. We introduce the crossing-success-rate (CSR) to quantify the performance in water crossing. Our study suggests that more focus should be directed towards the exploration of behavioral models for hominins, as directionality may be a more powerful factor for crossing a barrier than environmental opportunities alone. A prerequisite for this is to perceive the opposite shore. Furthermore, to provide a comprehensive understanding of hominin expansions, the CSR allows for the integration of results obtained from small-scale simulations into large-scale models for hominin expansion