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<p>The trophic structure of South American Late Pleistocene mammal communities has long posed an apparent energetic paradox: exceptionally high herbivore biomass combined with a scarcity of large carnivores and seemingly limited primary productivity. Here, this issue is re-examined using the Arroyo del Vizcaíno Local Fauna (Uruguay), an unusually rich and minimally time-averaged Lujanian assemblage dated to the end of Marine Isotope Stage 3. Population densities, standing crop biomass and energetic demands were estimated using established allometric relationships, with explicit treatment of uncertainty through sensitivity and Monte Carlo analyses. Under baseline assumptions of strict herbivory, herbivore energetic demand approaches the upper bounds of plausible primary productivity for Late Pleistocene southeastern South America, while prey biomass exceeds the energetic requirements of the sole large carnivore, <i>Smilodon populator</i>. Sensitivity analyses show that absolute energetic estimates depend strongly on physiological parameters, but the qualitative imbalance is robust across a wide parameter space. Introducing partial omnivory in ground sloths produces a marked reduction in herbivore demand for primary productivity and substantially narrows the apparent mismatch between herbivore biomass and carnivore demand. Even modest proportions of animal-derived energy (10–30%) are sufficient to reconcile energetic requirements with conservative estimates of primary productivity and secondary production. These results support the hypothesis that some ground sloths were at least opportunistic consumers of animal matter, a strategy with disproportionate consequences for community-level energy flow. More broadly, they highlight the importance of dietary flexibility and non-analogue ecological interactions in shaping the trophic structure of South American Pleistocene megafaunas.</p>

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Trophic relationships among Lujanian mammals 30 years later: brief review and the example of the Arroyo del Vizcaíno local fauna

  • 期刊论文

  • 发表日期：

    2026年2月16日

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  • Richard A. Fariña

摘要

The trophic structure of South American Late Pleistocene mammal communities has long posed an apparent energetic paradox: exceptionally high herbivore biomass combined with a scarcity of large carnivores and seemingly limited primary productivity. Here, this issue is re-examined using the Arroyo del Vizcaíno Local Fauna (Uruguay), an unusually rich and minimally time-averaged Lujanian assemblage dated to the end of Marine Isotope Stage 3. Population densities, standing crop biomass and energetic demands were estimated using established allometric relationships, with explicit treatment of uncertainty through sensitivity and Monte Carlo analyses. Under baseline assumptions of strict herbivory, herbivore energetic demand approaches the upper bounds of plausible primary productivity for Late Pleistocene southeastern South America, while prey biomass exceeds the energetic requirements of the sole large carnivore, Smilodon populator. Sensitivity analyses show that absolute energetic estimates depend strongly on physiological parameters, but the qualitative imbalance is robust across a wide parameter space. Introducing partial omnivory in ground sloths produces a marked reduction in herbivore demand for primary productivity and substantially narrows the apparent mismatch between herbivore biomass and carnivore demand. Even modest proportions of animal-derived energy (10–30%) are sufficient to reconcile energetic requirements with conservative estimates of primary productivity and secondary production. These results support the hypothesis that some ground sloths were at least opportunistic consumers of animal matter, a strategy with disproportionate consequences for community-level energy flow. More broadly, they highlight the importance of dietary flexibility and non-analogue ecological interactions in shaping the trophic structure of South American Pleistocene megafaunas.