Esteban Soibelzon

ANNUAL DIET OF THE LITTLE HAIRY ARMADILLO, CHAETOPHRACTUS VELLEROSUS (MAMMALIA, DASYPODIDAE), IN BUENOS AIRES PROVINCE, ARGENTINA

Abstract Analysis of the stomach contents of 28 little hairy armadillos (Chaetophractus vellerosus), collected during a 14-month period at Pipinas, Argentina, showed that about 63.6% of the weight of prey items was composed of animal remains, 18% was plant material, and the remaining 18.4% was undetermined organic remains. Insects were the most frequent diet item, followed by plant material, amphibians, reptiles, and lastly birds and mammals in similar proportion. During autumn, plant material was the most abundant item, followed by vertebrates and invertebrates. During winter invertebrates prevailed, followed by a lower percentage of vertebrates and scarce plant remains. Invertebrates also were predominant during spring, whereas plant material and vertebrates composed very low percentages.

Continental Vertebrates During the Marine Isotope Stage 3 (MIS 3) in Argentina

Paleontological sites in Argentina with continental vertebrates corresponding to the Marine Isotope Stage 3 (MIS 3) interval are scarce or poorly known. This situation is mainly due to the lack of absolute ages for Pleistocene fossil remains or their bearing sediments that would allow the verification of the chronology established for this interval. However, a few isolated evidences show that continental vertebrates responded to the abrupt temperature changes that characterized the MIS 3 (Heinrich colder events and Dansgaard–Oeschger warmer events). Up to date, continental vertebrate remains of this age have been found mainly in Buenos Aires province, but also in a few sites of northeastern Argentina (such as Entre Rios, Corrientes, Formosa and Chaco provinces). In Buenos Aires province: (1) Paso Otero, in the Rio Quequen Grande valley, evidence of warmer and more humid conditions were found in sediments dated in 37,800 ± 2300 radiocarbon years before present (RCYBP); (2) Mar del Sur, General Alvarado County, coastal marine sediments with continental mammals were dated in 25,700 ± 800 and 33,780 ± 1200 RCYBP; (3) Balneario Saldungaray, in the Rio Sauce Grande valley, Tornquist County, gastropods associated with mammal remains were dated in 32,300 ± 1800 and 27,500 ± 670 RCYBP; (4) Los Pozos, Marcos Paz County, sediments dated between 29,000 and 33,000 RCYBP are associated with remains of mammals , birds, reptiles and amphibians; (5) San Pedro, San Pedro County, sediments bearing vertebrate fauna have two OSL datings of 37,626 ± 4198 and 41,554 ± 3756 years B.P. (YBP). In Entre Rios province, Rio Ensenada valley, Diamante Department, some levels of the Tezanos Pinto Formation with OSL datings between 9000 and 35,000 YBP yielded remains of grazer megamammals and other taxa characteristic of the modern Patagonian Domain. In the province of Corrientes, Arroyo Toropi, Bella Vista, vertebrate remains dated with OSL from 36,000 to 52,000 YBP show a clear taxonomic change in response to climatic fluctuations. In Formosa province, Rio Bermejo, Villa Escolar sediments of the Fortin Tres Pozos Formation, bearing vertebrate fauna have an OSL age of 58,160 ± 4390 YBP. In the province of Chaco, Charata locality, gastropods associated with mammal remains were dated between 22,000 and 27,000 RCYBP. A larger amount of absolute datings of the bearing sediments and especially taxon dates are needed to determine more accurately the response of the fauna to the climate changes characteristic of MIS 3.

The GABI in Southern South America

The Great American Biotic Interchange (GABI) between North and South America is one of the most important events in the history of land mammals. The interchange occurred in several phases during more than nine million years. We here analyze the chronology and dynamics of the GABI, the evolution of some South American mammalian groups through time, and the Quaternary mammalian extinctions. As the GABI was a complex process, we divide it into ProtoGABI and GABI 1 to 4. In our concept, the extinction of the megafauna by the gatherer/hunters that entered South American during the latest Pleistocene is a part of the GABI. The putative scarce frequency of extinct mammals in archeological sites is discussed. The evolutive relevance of the GABI is reflected in that half of the species living in South America had a North American ancestry. A final process, not included in the GABI, is the remarkable alteration of ecosystems by modern man. Presently, the composition and distribution of almost all autochthonous land mammal faunas are changing dramatically. Moreover, frequently they are replaced with domesticated and/or wild exotic species.

Continental Relationships, Chronostratigraphy, Climates, and Mammalian Biogeography of Southern South America Since Late Miocene

The biotic interchange between the Americas occurred in several phases during more than nine million years. In this book, we focus on mammals of southern South America, where the most important and richest localities with fossil vertebrates of Late Miocene–Holocene Age were reported. We here provide basic information about taxonomic composition, biostratigraphy, climate evolution, continental tectonics, and biogeography for better understanding the GABI. Furthermore, we analyze the chronology and dynamics of the GABI, the evolution of some South American mammalian groups through time, and the Quaternary mammalian extinctions. As the GABI was a complex process, we divide it into ProtoGABI and GABI 1 to 4.

Aggregation of mummified adult crabeater seals (Pinnipedia: Phocidae) in the eastern Antarctic Peninsula: age and sex structure, taphonomy and cause of death

Abstract In Antarctica, crabeater seals tend to strand as immature animals with disorientation, due to their inexperience, given as the probable cause. In 2012 and 2013, we examined a group of 80 mummified crabeater seals on Seymour Island (Marambio). The age and gender of 28 seals was determined, and virology and stomach content analyses were performed in order to determine the cause of stranding. Around 82% of the seals examined were adults and 79% were females, some of which were pregnant. All of the seals sampled tested negative for Morbillivirus, suggesting that the stranding was not related to the mass mortality event reported in the 1950s in the region. Most seals had empty stomachs and thin blubber suggesting that they died from starvation. The state of the carcasses suggests multiple stranding events. Most of the seals were located along an ice-covered stream, suggesting that this may act as a ‘natural trap’, isolating the seals from the open ocean. This is exceptional as it is the first report of mostly adult female seals to strand in Antarctica and refutes the theory that only young animals are prone to stranding.