Keyword: Rodentia

Eating like a girl: sex differences in the diet of the lesser grison (Galictis cuja) in southern Brazil

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The lesser grison is a hypercarnivore mustelid that is widespread in South America, inhabiting a large variety of habitats, including steppes, deserts, grasslands, forests, and swamps. However, there are few scientific data on the ecology of the species. In our study, we investigate the feeding habits of the Galictis cuja in the Brazilian Pampas by analyzing the stomach contents of road-killed individuals collected from 2013 to 2023. We identify a high consumption of mammals found in 80% of the samples, comprising 75% of the prey  consumed. Amphibians, reptiles, and birds are consumed in smaller proportions. Regarding mammals, only rodents were consumed, among which Cavia sp., Holochilus brasiliensis, and Rattus sp. stand out, corresponding to 62% of biomass intake. Although there was no sexual difference in the prey consumed, we found a difference in predation rate, with males consuming more Rattus and females consuming more Cavia. As a result, males are consuming prey that is proportionally smaller (equivalent to 1/6 of their own weight) than that of females (1/3 of their own weight). This is contrary to what is expected due to the sexual dimorphism of the species; in other mustelids, males consume the larger prey.

Comendo como uma menina: diferenças sexuais na dieta do furão (Galictis cuja) no sul do Brasil. O furão-pequeno é um mustelídeo hipercarnívoro amplamente distribuído na América do Sul, ocorrendo em uma variedade de habitats, incluindo estepes, desertos, campos, florestas e áreas úmidas. Todavia, há poucos dados científicos sobre a ecologia da espécie. Nesse estudo investigamos os hábitos alimentares de Galictis cuja na região do Pampa brasileiro, pela análise de conteúdo estomacais de indivíduos encontrados atropelados entre os anos de 2013 e 2023. Identificamos um alto consumo de mamíferos, encontrados em 80% das amostras e compreendendo 75% das presas consumidas. Anfíbios, répteis e aves são consumidos em baixas proporções. No que se refere aos mamíferos, apenas roedores foram encontrados, dentre os quais Cavia sp., Holochilus brasiliensis e Rattus sp. se destacam, correspondendo a 62% da biomassa ingerida. Apesar de não terem sido encontradas diferenças nas presas consumidas por machos e fêmeas, foram encontradas diferenças nos padrões de predação, com machos consumindo mais Rattus e fêmeas consumindo mais Cavia. Como resultado, machos consomem presas proporcionalmente menores (equivalentes a 1/6 de seu peso) do que as fêmeas (com presas equivalentes a 1/3 de seu peso). Isso é contrário ao esperado dado o dimorfismo sexual de tamanho existente nessa espécie e ao observado em outros mustelídeos, em que os machos consomem presas maiores.

Graphical abstract for the article “Eating like a girl: sex differences in the diet of the lesser grison (Galictis cuja) in southern Brazil” (B.M. Rodrigues et al., 2024)

Anthropogenic changes in land use and their consequences on rodent populations reservoirs of zoonotic viruses

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The ecology of animal host species can be altered when their habitats are modified, affecting the transmission of their pathogens and the probability of disease risk in the human population. Predicting how zoonotic diseases emerge and spread in response to anthropogenic land use changes requires an understanding of how these changes influence hosts and pathogens. The objective of this paper is to analyze how urbanization, agricultural intensification, and invasive species have favored the increase in population abundance of host species and the transmission of zoonotic viruses. This work seeks to synthetize research conducted from the 1990s to the present day in different regions of Argentina on species of rodent reservoirs of the viruses that cause Argentine Hemorrhagic Fever, Lymphocytic Choriomeningitis and Hantavirus Pulmonary Syndrome. The data collected link the ecology of their host species, Calomys musculinus, Mus musculus, and Oligoryzomys longicaudatus, to anthropogenic processes in different types of environments (rural, urban, peri-urban, semi-natural, and natural).

Cambios antropogénicos en el uso de la tierra y sus consecuencias en poblaciones de roedores reservorios de virus zoonóticos. La ecología de especies animales hospedadoras puede alterarse cuando se modifican sus hábitats, y se afectan la transmisión de sus patógenos y la probabilidad de riesgo de enfermedad en la población humana. Predecir cómo surgen y se propagan las enfermedades zoonóticas en respuesta a los cambios antropogénicos del uso de la tierra requiere una comprensión de cómo estos cambios influyen en los hospedadores y patógenos. El objetivo del presente estudio es analizar cómo la urbanización, la intensificación agrícola y la introducción de especies exóticas han favorecido el aumento de la abundancia poblacional de especies hospedadoras y la transmisión de virus zoonóticos. Este estudio busca realizar una síntesis de las investigaciones desarrolladas desde la década de 1990 hasta la actualidad en diferentes regiones de Argentina sobre especies de roedores reservorios de los virus que producen fiebre hemorrágica argentina, coriomeningitis linfocitaria y síndrome pulmonar por hantavirus. Los datos relevados vinculan la ecología de sus especies hospedadoras Calomys musculinus, Mus musculus y Oligoryzomys longicaudatus, y su relación con los procesos antropogénicos en diferentes tipos de ambientes (rurales, urbanos, periurbanos, seminaturales y naturales).

Graphical abstract for the article “Anthropogenic changes in land use and their consequences on rodent populations reservoirs of zoonotic viruses” (Gomez et al., 2024)

Review of tick species in two small synanthropic mammals, Didelphis albiventris (Lund, 1840) and Rattus rattus (Linnaeus, 1758)

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The present study aims to make a literature review, for the years between 1960 and 2022, of tick species that affect two species of small synanthropic mammals. A scientific literature review was carried out on the ticks that affect the species Didelphis albiventris (Lund, 1840) and Rattus rattus (Linnaeus, 1758), covering the years 1960 to 2022. The main countries that contributed to studies on the subject were: Brazil (N = 48), corresponding to 84% of the articles found, then Argentina, Angola, Madagascar, Sri Lanka, Australia, Italy, Singapore, the United States, and Taiwan, each contributing with one article (N = 1), representing 2% each of the articles found, totaling 16% remaining. We also observed differences between the percentages of studies on the small mammal species surveyed, with 77% carried out with the species D. albiventris, and 23% referring to R. rattus. Considering only the studies carried out in Brazil, which corresponded to 84%, Atlantic Forest and Cerrado seem to be the biomes with the most published studies, with ticks for both host species (N = 34) 47% and (N = 30) 42%, respectively. 7% (N = 5) of the studies were found for the Caatinga biome and 4% (N = 3) for the Pampa biome.

Espécies de carrapatos em dois pequenos mamíferos sinantrópicos. O presente estudo tem como objetivo fazer uma revisão de literatura, para os anos de 1960 a 2022, das espécies de carrapatos que acometem duas espécies de pequenos mamíferos sinantrópicos. Foi realizada revisão da literatura científica sobre os carrapatos que acometem as espécies Didelphis albiventris (Lund, 1840) e Rattus rattus (Linnaeus, 1758), abrangendo os anos de 1960 a 2022. Os principais países que contribuíram com estudos sobre o tema foram: Brasil (N = 48), correspondendo a 84% dos artigos encontrados; depois por Argentina, Angola, Madagascar, Sri Lanka, Austrália, Itália, Cingapura, Estados Unidos e Taiwan, cada um contribuindo com um artigo (N = 1), representando 2% cada um dos artigos encontrados, totalizando 16% restantes. Também observamos diferenças entre os percentuais de estudos sobre as espécies de pequenos mamíferos pesquisadas, com 77% realizados com a espécie D. albiventris, e 23% referentes a R. rattus. Considerando apenas os estudos realizados no Brasil, que corresponderam a 84%, Mata Atlântica e Cerrado parecem ser os biomas com mais estudos publicados, com carrapatos para ambas as espécies hospedeiras (N = 34) 47% e (N = 30) 42%, respectivamente. 7% (N = 5) dos estudos foram encontrados para o bioma Caatinga e 4% (N = 3) para o bioma Pampa.

Graphical abstract for the article “Review of tick species in two small synanthropic mammals, Didelphis albiventris (Lund, 1840) and Rattus rattus (Linnaeus, 1758)” (Oliveira et al., 2024)

Los análisis de egagrópilas y su impacto en el conocimiento de los micromamíferos de la Patagonia

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Los micromamíferos representan uno de los componentes más importantes de las comunidades de vertebrados terrestres neotropicales. Una metodología muy utilizada para analizar la composición de sus ensambles y los parámetros que los caracterizan (i.e. riqueza, diversidad) es el análisis de egagrópilas de aves rapaces. En Argentina, uno de los pioneros en utilizar esta metodología fue Elio Massoia en la década de 1960. Desde entonces, los trabajos basados en el estudio de egagrópilas para obtener información sobre micromamíferos fueron en aumento. El objetivo de este trabajo es documentar cómo esta metodología cambió nuestro conocimiento sobre los micromamíferos patagónicos. Se revisó la bibliografía publicada sobre análisis de egagrópilas y estudios enfocados en micromamíferos para la Patagonia argentina. El material recuperado de las egagrópilas ha permitido analizar la variabilidad intraespecífica de especies poco representadas en colecciones de museos o difíciles de capturar mediante trampas. Esta herramienta cambió de forma extraordinaria nuestra percepción sobre la biogeografía y distribuciones geográficas de muchas especies patagónicas (e.g. Calomys musculinus, Galea leucoblephara, Graomys griseoflavus, Lestodelphys halli, Loxodontomys micropus, Microcavia australis, Notiomys edwardsii, Paynomys macronyx, Thylamys pallidior). Asimismo, permitió reconsiderar las categorías de conservación de algunas especies que se creían raras y que demostraron solamente estar subrepresentadas en los muestreos tradicionales (i.e. N. edwardsii, L. halli, Euneomys chinchilloides e Irenomys tarsalis). Finalmente, también nos ha permitido reconstruir la estructura de los ensambles y los cambios que han atravesado desde al menos el Pleistoceno Tardío, documentando retracciones regionales, variaciones dramáticas en las frecuencias relativas y cambios en la dominancia de especies en los conjuntos actuales como consecuencia del impacto antrópico. El análisis de egagrópilas de aves rapaces representa una herramienta poderosa, especialmente en áreas extensas que serían difíciles de prospectar mediante otros métodos.

The analysis of owl pellets and their impact on knowledge of micromammals from Patagonia. Micromammals represent one of the most important components of the Neotropical terrestrial vertebrate communities. A widely used methodology to analyze the composition of their assemblages and the parameters that characterize them (i.e., richness, diversity) is the analysis of pellets produced by birds of prey. In Argentina, one of the pioneers in using this methodology was Elio Massoia. From that moment on, the studies based on the study of pellets to obtain information on small mammals were on the rise. The objective of this work is to document how this methodology changed our knowledge about Patagonian micromammals. We reviewed the published bibliography on pellet analysis and studies focused on small mammals for Argentinian Patagonia. The material recovered from pellets has made it possible to analyze the intraspecific variability of species poorly represented in museum collections or diffcult to capture using traps. This tool also dramatically changed our perception of the biogeography and geographical distributions of many Patagonian species (e.g., Calomys musculinus, Galea leucoblephara, Graomys griseoflavus, Lestodelphys halli, Loxodontomys micropus, Microcavia australis, Notiomys edwardsii, Paynomys macronyx, Thylamys pallidior). Likewise, it allowed reconsidering the conservation categories of some species that were believed to be rare (i.e., N. edwardsii, L. halli, Euneomys chinchilloides, and Irenomys tarsalis). Finally, it has also allowed us to reconstruct the structure of the assemblages and the changes on them since at least the Late Pleistocene, documenting regional retractions, dramatic variations in relative frequencies, and changes in the dominance of species in recent assemblages as a consequence of the anthropic impact. Pellet analysis of birds of prey represents a powerful tool, especially in large areas that would be diffcult to survey by other methods.

Drawings and notes by Elio Massoia. Photo collage by Damián Voglino.

Reply to: Teta et al. (2020): on the distinction and availability of the new taxa proposed by Agnolin et al. 2019

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In a recent work Teta and collaborators conclude that all taxonomic decisions and new taxa established by Agnolin et al. should be considered invalid. It is not our aim to analyze point by point the critics and observations made by Teta et al., some of which we recognize are correct. In the present contribution we emphasize on the epistemological and philosophical flaws made by those authors. Teta et al. sustain their critics almost on authority criterion, acting as judge and jury on what works and what does not in mammalogy.We are convinced that without discussion there is a danger that any scientific discipline can be transformed in a dogma.

Respuesta a: Teta et al. (2020): Sobre la distinción y disponibilidad de los nuevos taxones propuestos por Agnolin et al. 2019. En una contribución reciente Teta y colaboradores concluyen que la totalidad de las decisiones taxonómicas y los nuevos taxones establecidos por Agnolin et al. deben ser considerados inválidos. No es nuestro fin analizar punto por punto las críticas y observaciones hechas por Teta et al., algunas de las cuales reconocemos son correctas. En la presente contribución enfatizamos en los errores epistemológicos y filosóficos cometidos por esos autores. Estamos convencidos de que sin discusión existe el peligro de que cualquier disciplina científica pueda ser transformada en un dogma.

Efecto de la condición social de alojamiento en cautiverio sobre comportamientos individuales: Calomys musculinus como especie modelo ecológico

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Numerosos estudios experimentales realizados en varias especies de mamíferos, pero principalmente en ratones y ratas de laboratorio, demostraron que el aislamiento social afecta profundamente los comportamientos individuales. Este estudio fue diseñado para comprender cómo los comportamientos agresivos y exploratorios de machos de Calomys musculinus, sexualmente maduros, podrían verse afectados por las condiciones de alojamiento. El estudio se realizó en bioterio durante marzo y mayo de 2018. Durante una semana, 35 machos fueron alojados en condición solitaria y 30 en condición agrupada (3 individuos por caja). Para estudiar el comportamiento de exploración se utilizó una cámara de desplazamiento. Para el estudio de agresividad, en una arena circular se realizaron enfrentamientos diádicos de 5 minutos de duración cada uno de ellos, entre individuos provenientes del mismo tratamiento. Los resultados obtenidos en este estudio experimental apoyaron la hipótesis planteada: los machos de C. musculinus alojados individualmente fueron más exploradores y menos agresivos que los provenientes de la condición agrupada. La mayor agresividad de los machos de C. musculinus alojados en grupo se vio reflejada por la intensidad de las aproximaciones ofensivas, ataques o persecuciones exhibidos durante los enfrentamientos intrasexuales. Nuestros resultados constituyen un aporte importante para la interpretación de futuros estudios en C. musculinus que requieran tanto del alojamiento transitorio de individuos, como del establecimiento de colonias fundadoras de breve permanencia en bioterio, de la conformación de una colonia bioterio o de la constitución de grupos experimentales.

Effect of the social status of housing in captivity on individual behaviors: Calomys musculinus as species ecological model. Several experimental studies conducted in various mammalian species, but mainly in laboratory mice and rats, demonstrated that social isolation deeply affects individual behaviors. This study was designed to understand how aggressive and exploratory behaviors of sexually mature Calomys musculinus males could be affected by housing conditions. The study was conducted in laboratory during March and May 2018. During one week, 35 males were housed in solitary condition and 30 in grouped condition (3 individuals per box). A displacement camera was used to study the scanning behavior. For the study of aggressiveness, dyadic confrontations of 5 minutes each were carried out in a circular arena, between individuals from the same treatment. The results obtained in this experimental study supported our hypothesis: C. musculinus males housed alone were more exploratory and less aggressive than those from the grouped condition. The greater aggressiveness of the C. musculinus males housed in a group was reflected by the intensity of the offensive approaches, attacks or persecutions exhibited during intra-sexual trials. Our results constitute an important contribution for the interpretation of future studies in C. musculinus that require both the transitory accommodation of individuals, the establishment of founder colonies of short stay in the bioterium, the formation of a bioterium colony, or the constitution of experimental groups.

Graphical abstract for the article “Efecto de la condición social de alojamiento en cautiverio sobre comportamientos individuales: Calomys musculinus como especie modelo ecológico” (Battistini et al., 2021)

Small mammals in restinga areas of north-eastern Brazil

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The restingas are an important component of the Atlantic Forest, affected by anthropic impacts along the Brazilian coast. The mastofauna that occurs in these environments is little known, especially in the north-east of the country. This study characterized the richness, abundance and composition of small mammal species in arboreal restinga areas in the state of Sergipe, north-eastern Brazil. Sampling was performed monthly, from September 2017 to August 2018. An effort composed of 8188 trap-nights with Sherman traps and 1782 trap-nights with pitfall traps resulted in the capture of 120 individuals from 10 species: four marsupials (Didelphis albiventris, Marmosa demerarae, Marmosa murina, and Marmosops incanus) and six rodents (Calomys sp., Cerradomys vivoi, Oligoryzomys sp., Phyllomys blainvilii, Rhipidomys mastacalis, and Trinomys sp.). Phyllomys blainvilii is a new record for the state. The observed richness corresponds to 73% of that estimated by Jackknife 1 (13.6 ± 1.5 species). Marmosops incanus and R. mastacalis were the most abundant, corresponding to 84% of the individuals captured. The community composition differs from the restingas of other regions of Brazil, but the majority of the species correspond to a subset of those found in the Atlantic Forest of the region. The locality presented the greatest richness of small mammals in areas of the Atlantic Forest of Sergipe, reinforcing the importance of the preservation of these areas and contributing to understanding the mastofauna in the restingas. This study also presents an updated list for this group in the state.

Pequenos mamíferos em áreas de restinga no nordeste do Brasil. As restingas são um componente importante da Mata Atlântica, sendo afetadas por impactos antrópicos ao longo da costa brasileira. A mastofauna que ocorre nesses ambientes ainda é pouco conhecida, principalmente no nordeste do país. O presente estudo caracterizou a riqueza, abundância e composição de pequenos mamíferos em uma fitofisionomia de restinga arbórea em Sergipe, nordeste do Brasil. A amostragem foi realizada mensalmente de setembro de 2017 a agosto de 2018. O esforço de 8188 armadilhas-noite e 1782 pitfalls-noite resultou na captura de 120 indivíduos pertencentes a 10 espécies: quatro marsupiais (Didelphis albiventris, Marmosa demerarae, Marmosa murina e Marmosops incanus) e seis roedores (Calomys sp., Cerradomys vivoi, Oligoryzomys sp., Phyllomys blainvilii, Rhipidomys mastacalis e Trinomys sp.). O registro de P. blainvilii é inédito para o estado. A riqueza observada corresponde a 73% da estimada por Jackknife 1 (13.6 ± 1.5 espécies). Marmosops incanus e R. mastacalis foram as espécies mais abundantes, correspondendo a 84% dos indivíduos capturados. A composição da comunidade difere das restingas de outras regiões do Brasil, mas a maioria das espécies corresponde a um subconjunto das encontradas nas áreas de Mata Atlântica da região. A localidade apresentou a maior riqueza de pequenos mamíferos em áreas da Mata Atlântica de Sergipe, reforçando a importância da preservação dessas áreas e contribuindo para o entendimento sobre a mastofauna que ocorre nas restingas. Este estudo apresenta assim uma lista atualizada de pequenos mamíferos para o estado.

On the distinction and availability of the new taxa proposed by Agnolin et al. 2019

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Recently, Agnolin et al. (2019) described 14 new species of mammals, including 12 rodents, one bat, and one carnivore, and one new subspecies of rodent. In addition, these authors proposed several other nomenclatorial acts: some nominal forms were removed from synonymies and hypothesized as distinct species, at the time that three new genera, one subtribe, and one tribe of mammals were also named. We reviewed the merits of all nomenclatorial acts proposed by Agnolin at al. (2019) and concluded that all 14 new species and the new subspecies, as well as those forms removed from synonymies, should be treated as synonyms of already known species. We suggest the same regarding the three new supraspecific taxa presented by Agnolin et al., two of which are not available as they fail to comply with the provisions of the International Code of Zoological Nomenclature. We end this contribution criticizing the way that mammal taxonomy was approached by Agnolin et al. (2019).

Sobre la distinción y disponibilidad de los nuevos taxones propuestos por Agnolin et al. 2019. Recientemente, Agnolin et al. (2019) describieron 14 especies nuevas de mamíferos, incluyendo 12 roedores, un murciélago y un carnívoro, y una nueva subespecie de roedor. Además, estos autores propusieron varios otros actos nomenclatoriales: algunas formas nominales se eliminaron de las sinonimias y se hipotetizaron como especies distintas; se nombraron tres nuevos géneros, una subtribu y una tribu de mamíferos. Revisamos todos los actos nomenclatoriales propuestos por Agnolin et al. (2019) y concluimos que las 14 nuevas especies y la nueva subespecie, así como las formas eliminadas de las sinonimias, deben tratarse como sinónimos de especies ya conocidas. Sugerimos lo mismo con respecto a los tres nuevos taxones supraespecíficos presentados por Agnolin et al. (2019), de los cuales dos no están disponibles ya que no cumplen con las disposiciones del Código Internacional de Nomenclatura Zoológica. Terminamos esta contribución criticando la forma en que Agnolin et al. (2019) realizaron su abordaje taxonómico.

Use of forest fragments and agricultural matrices by small mammals in southeastern Brazil

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The use of matrix by species that naturally inhabit forest fragments can be an important instrument to restore connectivity in fragmented landscapes. The type and structure of the matrix are determinant for this connectivity, however, few studies have explored this theme. In this study, we evaluated the community of small mammals within forest remnants and within two types of matrices (coffee plantation and pasture). In all, 11 species of small mammals were captured, being Akodon montensis, Oligoryzomys nigripes and Calomys cerqueirai the most abundant in fragments, coffee plantation and pasture, respectively. The results show that the composition and structure of the community in the two matrix types are distinct from those found in fragments, and the coffee plantation matrix has greater abundance and greater richness of small mammals than the pasture matrix.

Uso de fragmentos florestais e matrizes agrícolas por pequenos mamíferos no sudeste do Brasil. O uso da matriz por espécies que naturalmente habitam manchas florestais pode ser um instrumento importante para restaurar a conectividade em paisagens fragmentadas. O tipo e a estrutura da matriz são determinantes para esta conectividade, porém, poucos estudos exploram este tema. Neste estudo, nós avaliamos a comunidade de pequenos mamíferos dentro de fragmentos florestais e também dentro de dois tipos de matrizes (plantação de café e pasto). No total foram capturadas 11 espécies de pequenos mamíferos, sendo Akodon montensis, Oligoryzomys nigripes e Calomys cerqueirai as mais abundantes nos fragmentos, plantação de café e pasto, respectivamente. Os resultados mostram que a composição e a estrutura da comunidade nos dois tipos de matrizes foram diferentes daquelas encontradas nos fragmentos, e que a matriz de café possui maior abundância e riqueza de espécies que a matriz de pasto.

Richness, endemism and conservation of sigmodontine rodents in Argentina

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Sigmodontine rodents, with 86 genera and ~430 living species, constitute one of the most successful radiations of Neotropical mammals. In this contribution, we studied the distributional ranges of 108 sigmodontine species in Argentina. Our objectives were (i) to establish geographical patterns of species richness and endemism, and (ii) to evaluate the regional conservation status of these taxa. We constructed a minimum convex polygon for each species, using information from literature and biological collections. Individual maps were superimposed on a map of Argentina divided into cells of 25 km on each side. For each cell, we calculated the species richness, which varied between 1 and 21 species, and its degree of endemism, which fluctuated between 0.001 and 3.28. There were 30 species of sigmodontine rodents distributed almost exclusively in Argentina, most of them restricted to forested areas (Southern Andean Yungas) or to arid and semiarid environments (High and Low Monte and Patagonian Steppe). Areas with high species richness and endemism scores corresponded grossly with the Southern Andean Yungas, the Humid Chaco plus the Paraná flooded savannas, the Alto Paraná Atlantic forests plus the Araucaria moist forests, the High Monte and the ecotone between the Patagonian steppe and the Valdivian temperate forests. A reassessment of the conservation status of sigmodontine rodents distributed in Argentina retrieved 2 extinct species, 7 endangered, 7 vulnerable, 6 near threatened and 13 data deficient. These numbers suggest a much more serious situation than the expressed by previous evaluations, highlighting the urgent need to establish conservation measures for the protection of this group.

Riqueza, endemismo y conservación de roedores sigmodontinos en Argentina. Los roedores sigmodontinos, con 86 géneros y ~430 especies vivientes, constituyen una de las radiaciones más exitosas de mamíferos neotropicales. En esta contribución estudiamos los rangos de distribución de 108 especies de sigmodontinos en Argentina. Nuestros objetivos fueron (i) establecer patrones geográficos de riqueza de especies y endemismo y (ii) evaluar el estado de conservación regional de estos taxones. Construimos un polígono convexo mínimo para cada especie, utilizando información de la literatura y colecciones biológicas. Los mapas individuales fueron superpuestos en un mapa de Argentina dividido en celdas de 25 km de lado. Para cada celda calculamos la riqueza de especies, que varió entre 1 y 21, y su grado de endemismo, que fluctuó entre 0.001 y 3.28. Hubo 30 especies de roedores sigmodontinos distribuidos casi exclusivamente en Argentina, la mayoría de ellos restringidos a áreas boscosas (Yungas andinas del sur) o a ambientes áridos y semiáridos (Monte alto y bajo y Estepa Patagónica). Las áreas con mayor riqueza de especies y valores más altos de endemismo se correspondieron groseramente con las Yungas andinas del sur, el Chaco húmedo más las Sabanas inundadas de Paraná, el Bosque Atlántico del Alto Paraná más los Bosques húmedos de araucaria, el Monte alto y el ecotono entre la Estepa Patagónica y los Bosques templados valdivianos. Una reevaluación del estado de conservación de los roedores sigmodontinos distribuidos en Argentina recuperó 2 especies extintas, 7 en peligro, 7 vulnerables, 6 casi amenazadas y 13 con datos deficientes. Estas cifras sugieren una situación mucho más grave que la expresada en evaluaciones anteriores, destacando la necesidad urgente de establecer medidas de conservación para la protección de este grupo.