Content area
Full Text
ABSTRACT-Arctotherium angustidens Gervais and Ameghino, 1880 (the South American giant short-faced bear) is known for being the earliest (Ensenadan Age, early to middle Pleistocene) and largest (body mass over 1 ton) of five described Arctotherium species endemic to South America. Here we assess the diet of this bear from multiple proxies: morphology, biomechanics, dental pathology, stable isotopes and a previous study using geometric morphometric methodology. Results favor the idea of animal matter consumption, probably from large vertebrates in addition to vegetable matter consumption. Most probably, active hunting was not the unique strategy of this bear for feeding, since its large size and great power may have allowed him to fight for the prey hunted by other Pleistocene carnivores. However, scavenging over mega mammal carcasses was probably another frequent way of feeding. South American short-faced bears adjusted their size and modified their diet through Pleistocene times, probably as a response to the diversification of the carnivore guild (from the few precursory taxa that crossed the Panamanian Isthmus during the Great American Biotic Interchange).
INTRODUCTION
South American short-faced bears (Ursidae.Tremarctinae) were represented by one genus (Arctotherium Burmeister 1879) and five species: A. angustidens Gervais and Ameghino 1880; A. wingei Ameghino 1902; A. vetustum Ameghino 1885; A. bonariense (Gervais 1848-1852) and A. tarijense Ameghino 1902 (Soibelzon, 2004), Of these, A. angustidens (the giant short-faced bear, hereafter "giant SFB") is the only species recorded in the early to middle Pleistocene (Ensenadan) of Argentina and in Pleistocene (?) sediments of Bolivia (Soibelzon et al., 2005), the other four species are recorded from the middle Pleistocene to the latest Pleistocene (Bonaerian and Lujanian) in Chile, Bolivia, Uruguay, Venezuela, Brazil, and Argentina (Soibelzon et al., 2005; Soibelzon and Rincón, 2007; Rodrigues et al., 2012). The only living representative of the Tremarctinae subfamily is the spectacled or Andean bear, Tremarctos ornatus (Cuvier, 1825).
Short-faced bears arrived in South America from North America through the Panamanian Isthmus during the Great American Biotic Interchange (Marshall et al., 1982) like all eutherian carnivores (Soibelzon and Prevosti, 2007, 2012; Prevosti and Soibelzon, 2012). By the early Pleistocene, there were only two very large mammalian predators (i.e., body mass over 200 kg) in South American ecosystems: the giant SFB, a gigantic carnivore-omnivore (body mass as high as...