Late-Holocene small mammals in the Humid Chaco of northern Argentina: Evidence of environmental stability in fluvial contexts inhabited by hunter-gatherer-fishers

Abstract

The small mammal assemblages from seven open-air archeological sites in the Argentinean Humid Chaco are analyzed from taphonomic, biogeographic and paleoenvironmental perspectives. The study employs standard taxonomic and taphonomic methodologies, complemented by Temporal Niche of Occurrence (NOO3D) analysis, diversity indices, and multivariate statistical techniques. Small mammal remains were accumulated at the archeological sites through both anthropogenic activities and natural in situ deaths. Despite good preservation due to rapid burial, the specimens exhibit evidence of trampling and root activity. With the specimens studied here, we expand the known Late-Holocene small mammal record in the Humid Chaco from four to seven taxa, reflecting the typical present day composition of this biome between 1,6 and 0,6 ka cal BP. The identified species are typical of flooded environments (Lutreolina crassicaudata, Holochilus brasiliensis, H. chacarius), open grasslands and sandy areas (Cavia aperea, Ctenomys sp.), hydrophytic vegetation (Scapteromys aquaticus), and gallery forests (Sooretamys angouya). The record of Sooretamys represents one of the few known fossil occurrences in South America, the second in Argentina, and the first in the Humid Chaco. Ecological niche models for this rodent support the persistence of the region’s fluvial system and gallery forests since the Pleistocene–Holocene boundary. Human groups inhabiting the Humid Chaco over the past 1600 years likely adapted their gathering, fishing, and hunting practices—including the exploitation of large, medium, and small vertebrates such as Cavia and Holochilus—along with their settlement strategies, to optimize resource use and reduce transportation costs in response to climatic cycles, including phases of increased rainfall.