Testing the hypothesis of an impoverished predator guild in the Early Miocene ecosystems of Patagonia: An analysis of meat availability and competition intensity among carnivores

Authors

Rodríguez-Gómez, G; Cassini, GH; Palmqvist, P; Bargo, MS; Toledo, N; Martín-González, JA; Muñoz, NA; Kay, RF; Vizcaíno, SF

Abstract

The lower Miocene Santa Cruz Formation (dated to ~18–16 Ma) of Southern Patagonia, Argentina, preserves rich vertebrate faunas, which are representative of communities that existed prior to the Great American Biotic Interchange (GABI). Some previous researchers have hypothesized that these pre-GABI faunas had a low richness of mammalian carnivores (an impoverished predator guild), while others argue for a predator/prey ratio similar to those of recent communities. In this paper, we analyze faunas from the lower part of the Santa Cruz Formation (FL 1–7) using a methodology that allows us to quantify (i) the meat resources that were available to the secondary consumers of the palaeocommunity; and (ii) the competition intensity for these resources. In our modeling, we considered different scenarios related to meat consumption, including the possibility that several taxa had a scavenging behavior, and also differences in mortality rates between young and adult prey. Our results provide estimates of the nutritional requirements from the predator/scavenger guild under maximum and minimum quantities of meat offered by the prey community, which indicate the presence of a well-balanced palaeocommunity. Moreover, the competition indices point to a relatively high level of competition for prey of small-to-medium size, although competition for resources from large mammal prey was rather low. This suggests that the predator/scavenger guild was not impoverished, although there were insufficient carnivore species to fully consume the megaherbivore biomass.

Citation

Rodríguez-Gómez, G., G. H. Cassini, P. Palmqvist, M. S. Bargo, N. Toledo, J. A. Martín-González, N. A. Muñoz, R. F. Kay, and S. F. Vizcaíno. “Testing the hypothesis of an impoverished predator guild in the Early Miocene ecosystems of Patagonia: An analysis of meat availability and competition intensity among carnivores.” Palaeogeography, Palaeoclimatology, Palaeoecology 554 (September 15, 2020). https://doi.org/10.1016/j.palaeo.2020.109805.