Volumen y Número: Vol. 1

Camélidos silvestres y mortalidad por tormentas de nieve en la cordillera frontal de la provincia de San Juan, Argentina

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Se discute el efecto de eventos climáticos, tal como los temporales de nieve, sobre poblaciones de camélidos silvestres. Las tormentas de nieve del año 1984 causaron la mortandad, directa e indirecta, de 181 camélidos: 148 vicuñas (Vicugna vicugna) y 33 guanacos (Lama guanicoe) en un área bajo estudio de la Reserva de la Biósfera de San Guillermo, Provincia de San Juan, Argentina. Analizando la mortandad en vicuñas, no se encontró diferencias significativas por sexo, pero si mayor mortalidad (P < 0.001) en los juveniles (< 1 año de edad). El hábitat de quebradas mostró una marcada vulnerabilidad (P < 0.001) en comparación con llanos y vegas para ambas especies. Los números de camélidos muertos representaron el doble de lo encontrado en la misma área en seis años anteriores, aunque en términos poblacionales constituyen el 4.5% (vicuña) y el 1% (guanaco) de la población censada previamente.

This study deals with the effects of snowstorms on the population structure of wild camelids. The severe winter storms of 1984 influenced the mortality (direct and indirect) of 184 camelids: 148 vicuñas (Vicugna vicugna) and 33 guanacos (Lama guanicoe) in the San Guillermo Biosphere Reserve, San Juan Province, Argentina. Considering vicuña mortality, no significant differences were found in mortality by sex; juveniles (< 1 year old) were significantly affected (P < 0.001). Considering both species, more dead animals were found in gullies (P < 0.001) than in other habitats (plains and marshes). The number of deaths in 1984 was twice that found in the same area during the previous six years, representing 4.5% and 1% of the censused vicuña and guanaco populations respectively.

Patrones reproductivos y alimenticios de dos especies simpátricas del género Sturnira (Chiroptera, Phyllostomidae)

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Reproductive patterns and feeding habits are reported for two sympatric species of bats in the genus Sturnira (Chiroptera, Phyllostomidae). Reproductive patterns of S. lilium and S. erythromos, in the southern portion of their distribution, are not coincident with data reported by other authors for the species in other latitudes. In general, feeding habits are poorly known. Diet selection in Río Las Piedras, Horco Molle, Province of Tucumán is related to patterns of reproduction.

Las homologías en los diseños oclusales de los roedores Caviomorpha: un modelo alternativo

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The problem of loph homologies among the upper cheek teeth of the caviomorph rodents and the polarity of some of the observed changes are reanalyzed. This analysis is made upon the evidences provided by both living and fossil representatives. It is concluded that pentalophodonty is an homology for the caviomorphs. There is only one pentalophodont pattern, while there are two different tetralophodont configurations. In all of them, the third loph is a mesoloph. The tetralophodont patterns represent successive steps of a general process of loph reduction. In brachyodont molars, this reduction is part of the adaptation to open environments, such as the development of hypsodonty is. The scarcity of pentalophodont genera in the fossil record and their present restriction to the Brazilian subregion are related to the early development of open environments in the southern part of South America.

Nuevos aportes para el conocimiento de la mastofauna del Parque Nacional Calilegua (Provincia de Jujuy, Argentina)

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Seventy-four species of mammals are cited after two surveys trips to Calilegua National Park, Ledesma and Valle Grande Departaments, Province of Jujuy, Argentina. The information was completed with a deep bibliography research and personal comments. The mammal community presents differences in its composition in relation with the altitude and the phytogeographical structure. In the transition forest (500 m altitude) occurs the majority of the species (62%), with an important chacoan fauna ingression. Excepting Rodentia, all the orders show decreased values to higher altitudes. Systematic and taxonomic information of the species are analyzed.

Feeding habits of Calomys musculinus in the crop fields and its borders

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The aim of this study was to investigate the diet of Calomys musculinus in crop fields and their borders, and its relationship to availability in these habitat types. Vegetation censuses were carried out, and microhistological analysis of the stomach contents of captured animals. C. musculinus presented a granivore diet, with oligophagous behaviour, basing its consumption mainly on two seed species: Chenopodium sp. and Amaranthus sp. A marked correlation between plant availability and the items consumed by C. musculinus was not shown, although it was found that the weeds of the habitat were important food sources.

El objetivo de nuestro trabajo fue estudiar la dieta de Calomys musculinus en el ambiente de cultivo y sus bordes en relación a la disponibilidad vegetal de estos ambientes. Para ello se realizaron censos vegetales y se utilizó el análisis microhistológico de los contenidos estomacales. C. musculinus presentó una dieta granívora, con un comportamiento oligófago, basando su consumo principalmente en dos especies de semillas: Chenopodium sp. y Amaranthus sp. No se encontró una marcada correlación entre la disponibilidad vegetal y los items consumidos, siendo las malezas del hábitat importantes como fuente de alimento.

Conservación de la fauna de tetrápodos II: estado de conservación de los mamíferos del Parque y Reserva Nacional Nahuel Huapi

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The conservation status of the fauna of mammals of the Nahuel Huapi National Park and Reserve is evaluated in the present work. All 32 resident and 5 marginal mammals in the study area were considered in the methodology which consists in assessing the degree of conservation of each species through an index made up by 12 survival-related variables. A list of species ordered according to their conservation indices for Argentina was obtained. The addition of two variables accounting for the particular situation of the species within the study area, allowed the elaboration of another list showing the conservation requirements for the Park and Reserve. Both ordinations were similar. The species in most critical conservation situation are the «huemul patagónico» (Hippocamelus bisulcus), the «huillín» (Lutra provocax), the «tuco-tuco colonial» (Ctenomys sociabilis) and the «gato huiña» (Felis guigna). The variables of the greatest influence upon the value of the index are those related to distribution and space-use plasticity. The results were compared with conservation evaluations of the same species made by other researchers and institutions. Differences and similitudes between evaluations were detected. Both the index value and its component variables provide an useful tool in making decisions for conservation and management.

Conservación de la fauna de tetrápodos I: un índice para su evaluación

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This paper presents a methodology for ranking species according to conservation priorities, based on explicit, quantifiable criteria. Species are ranked through an index which is a sum of values assigned to 12 factors relevant to their survival: continental distribution, national distribution, extent of the use of habitat, extent of the use of vertical space, body size, reproductive potential, trophic amplitude, abundance, taxonomic singularity, singularity, extractive action and degree of protection of the species. The method was applied to 141 autochthonous tetrapod species of the Argentine Nothofagus forests. Results were compared to other qualifications by international and national organizations. The method is objective, and therefore repeatable and verifiable. It can be updated as new information becomes available. It is a useful guide for conservation and management, and because of its simplicity can expeditiously respond to concrete requirements. If the circumstances under which the method was calculated persist, it may become predictive.

Estudios paleoneurológicos en marsupiales «carnívoros» extinguidos de América del Sur: neuromorfología y encefalización

The South American marsupials exhibited a great diversity of forms during the major part of the Cenozoic. The marsupials which played the ecological role of terrestrial carnivores are found in the extinct families Borhyaenidae and Thylacosmilidae. Endocranial casts reflecting the brains of Borhyaena tuberata and Thylacosmilus atrox are studied. These endocasts show a well developed neocortex with a complex sulcal pattern. The inferred encephalic complexity is sufficient to include these brains in one of the three basic neuroanatomical morphologies which characterize living Australian marsupials: the Diprotodonta (exclusive of Macropodidae) type. The relative brain sizes of B. tuberata and T. atrox are large for polyprotodonts, being its encephalization quotients and progression indices the same or slightly aboye the average values for living diprotodonts. It is proposed here that during the Cenozoic in South America certain polyprotodont marsupials developed brains with similar patterns to those found in most living Australian diprotodont marsupials. It is congruent with the high specializations of the Borhyaenoidea during the Tertiary.