Visón americano: un nuevo invasor del Río Negro, Patagonia argentina

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El visón americano (Neovison vison) es el carnívoro exótico invasor de mayor distribución en Patagonia. Basados en relevamientos de campo y archivos históricos se presenta información detallada sobre su actual distribución en 180 km del Río Negro. Este foco representa la distribución más noreste, un nuevo ambiente invadido (Monte Oriental) y una nueva provincia con poblaciones silvestres (Buenos Aires). Documentamos la existencia de un criadero en las ciudades de Carmen de Patagones y Viedma (1965–1974), que podría ser el origen de este foco. Recomendamos diseñar e implementar planes de monitoreo y control de manera urgente.


American mink: a new invader of Rio Negro, Argentine Patagonia. American mink (Neovison vison) is the most widespread invasive carnivore in Patagonia. Based on field surveys and historical records, we present novel and detailed information of the American Mink present distribution along 180 km of the Río Negro. This invasion nucleus represents the most northeastern area recorded for the species, a new invaded ecoregion (Monte Oriental) and a new province with wild populations (Buenos Aires). We document the existence of a fur farm located in Carmen de Patagones and Viedma cities (1965–1974) that may have originated this focus. We recommend the prompt design and implementation of a control plan.

Armadillos as natural pests control? Food habits of five armadillo species in Argentina

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Armadillos are among the most common mammals in agroecosystems in Argentina. Their insectivorous/omnivorous food habits raise the question about their putative role as pest controllers. The aim of this study is to describe the prey items of five armadillo species and evaluate their possible role as natural pest controllers. The stomach contents of 12 Dasypus hybridus, 10 Chaetophractus vellerosus, 14 Chaetophractus villosus, 4 Tolypeutes matacus and 9 Zaedyus pichiy were analyzed. We described the diet and identified prey items to family level, whenever possible, and computed the frequency of occurrence (FO) and relative abundance of prey items. With these values, the Item Categorization Index (ICI) was calculated to classify the items in order of importance (primary, secondary and tertiary items). Shannon diversity index was also computed. The armadillos studied here consumed arthropod species belonging to families of phytosanitary importance such as Acrididae, Scarabaeidae, Tenebrionidae, Lepidoptera, Formicidae, and Termitidae. Only two armadillos showed primary items in their diet; Z. pichiy (ants and tenebrionids) and T. matacus (termites and scarabid larvae). Important pest arthropods had FO values close to or greater than 50% in the diet of all armadillos. Armadillos consumed arthropods that are important pests for agriculture, forestry, and wood construction. Even though this study was mainly focused on armadillos’ diet, we suggest that the presence of these native species could benefit the productivity and health of agroecosystems by reducing the need for harmful agrochemicals.


¿Son los armadillos controladores naturales de plagas? Hábitos alimentarios de cinco especies de armadillos en la Argentina. Los armadillos son algunos de los mamíferos más comunes en los agroecosistemas de Argentina. Sus hábitos alimentarios omnívoro/insectívoros sugirieron la pregunta acerca de su rol como presuntos controladores de plagas. El objetivo de este trabajo es describir la dieta de cinco armadillos y evaluar su posible rol como controladores de plagas. Se analizaron los estómagos de 12 Dasypus hybridus, 10 Chaetophractus vellerosus, 14 Chaetophractus villosus, 4 Tolypeutes matacus y 9 Zaedyus pichiy. Se identificaron los ítems presa hasta el nivel de familia cuando fue posible. Se estimó la frecuencia de ocurrencia (FO) y la abundancia relativa. Con estos valores se calculó el Índice de Categorización de Ítems (ICI) para clasificar las presas siguiendo un orden e importancia (primarias, secundarias y terciarias). También se calculó el índice de diversidad de Shannon. Los armadillos consumieron especies de artrópodos pertenecientes a familias de importancia fitosanitaria como Acrididae, Scarabaeidae, Tenebrionidae, Lepidoptera, Formicidae y Termitidae. Solo dos armadillos mostraron ítems primarios en su dieta: Z. pichiy (hormigas y tenebriónidos) y T. matacus (termitas y larvas de escarábidos). Los artrópodos plaga encontrados en la dieta de los armadillos tuvieron una FO cercana o superior al 50%. Los armadillos consumieron especies de artrópodos que son plagas importantes para la agricultura, la industria forestal y la construcción maderera. Aunque este estudio estuvo enfocado principalmente a la dieta de armadillos, sugerimos que la presencia de estas especies nativas podría beneficiar la productividad y salud de los agroecosistemas, reduciendo la necesidad de de utlizar agroquímicos perjudiciales.

Variabilidad genética de visones americanos Neovison vison asilvestrados en la provincia de Santa Cruz: ¿se cumple la paradoja genética de las especies invasoras?

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Las especies invasoras constituyen una amenaza para la biodiversidad nativa. El éxito de las especies invasoras pese a su baja variabilidad genética se conoce como «paradoja genética». El visón americano (Neovison vison) fue introducido en varias regiones del planeta como Europa, Asia y América del Sur con fines peleteros. En Argentina fue introducido en la década de 1930 y, como resultado de la liberación de individuos en la naturaleza, lograron establecerse poblaciones silvestres en la región patagónica. El objetivo del presente trabajo es estudiar la diversidad genética de una población asilvestrada de la provincia de Santa Cruz y compararla con la de una población en cautiverio. Analizamos un fragmento de 359 pb de la región control de ADN mitocondrial y encontramos índices de variabilidad similares entre la población silvestre y la población cautiva. Al igual que en poblaciones asilvestradas de otras regiones del planeta, no se observa una reducción en la variabilidad genética en la población silvestre de Santa Cruz, probablemente como consecuencia de liberaciones y escapes recurrentes desde diversas fuentes de cautiverio.


Genetic variation of wild American mink (Neovison vison) in the Province of Santa Cruz. Is the genetic paradox of invasive species met? Alien species represent a threat to native biodiversity. The success of invasive species despite their reduced genetic diversity is known as “the genetic paradox”. The American mink (Neovison vison) was introduced in several regions of the world, like Europe, Asia and South America. In Argentina, they were introduced in the 1930s by the fur industry and wild populations were established in Patagonia due to liberations and escapes. In this study, we analyzed the genetic diversity of a wild American mink population of northern Santa Cruz Province and compared it with a captive population. We sequenced a 359-bp fragment of the mtDNA control region and found that genetic variability was similar between both groups. Like in other wild invasive populations, genetic variability was not reduced in the population of Santa Cruz, probably as a consequence of frequent releases and escapes from different sources of captive minks.

Origin and history of the beaver introduction in South America

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The introduction of the North American beaver (Castor canadensis) to Tierra del Fuego is a widely known example of a successful biological invasion. However, the origin and history of this introduction bears closer scrutiny. Using historical documentation we provide evidence that beaver introduction occurred as a single release event of 20 beavers from northern Manitoba, Canada. This not only clarifies the origin of the invasion, but also suggests that the beaver population of Patagonia descends from a smaller number of individuals than previously assumed.


Origen e historia de la introducción del castor en América del Sur. La introducción del castor norteamericano (Castor canadensis) en Tierra del Fuego es un ejemplo ampliamente conocido de una invasión biológica exitosa. Sin embargo, el origen y la historia de su introducción merecen mayor análisis. Usando documentación histórica, presentamos evidencia de que la introducción del castor se originó en un único evento de liberación de 20 castores que arribaron desde el norte de Manitoba en Canadá. Esto no solo aclara el origen de la invasión, sino que sugiere que la población de castores en Patagonia deriva de un número de individuos menor que el que se asumía hasta el momento.

Expansión poblacional de una especie introducida en la Argentina: la ardilla de vientre rojo Callosciurus erythraeus

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Population expansion of an exotic mammal in Argentina: the Red-Bellied Squirrel Callosciurus erythraeus. Biological invasions are one of the major threats to biodiversity and ecosystem functioning, and they provoke economic losses to productive systems. A wild population of the Red-Bellied Squirrel Callosciurus erythraeus, native to South-east Asia, has established in the Province of Buenos Aires (Argentina) since 1973. The objective of this study is to assess the spatial distribution of the Red-Bellied Squirrel and describe the opinion of local inhabitants regarding the presence of this exotic species. We conducted 312 interviews in the district of Luján (original release site of this species) and other neighbouring districts, between August 2003 and March 2004. The area of the range distribution of squirrels was calculated using the minimum convex polygon method in a geographical information system. The present distribution of the Red-Bellied Squirrels (the only squirrel species present in this region) covers an area of approximately 680 km2. The increment of the radial distribution of squirrels was larger during the last five years (1999–2004: 1.6 km/year) than in a previous period (1973–1999: 0.3 km/year). While some inhabitants and local producers reported that the squirrels caused economic damages (e.g. in fruit plantations, afforestations, electric and irrigation systems), other inhabitants enjoy the presence of this species given its ornamental value, as a pet and even as a tourist attraction. The latter may encourage the transport of squirrels creating new invasive points, as has already occurred in the province of Córdoba (Argentina), and generating one of the major difficulties to prevent further expansion of this species.

Uso de trampas de pelo y caracterización de los pelos de la ardilla de vientre rojo Callosciurus erythraeus

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Use of hair tubes and hair characterization of the Red-Bellied Squirrel Callosciurus erythraeus. The Asiatic Red-Bellied Squirrel has been introduced into the Pampas Region, where a wild population has now been established and is colonizing new areas. Hair tubes have been successfully used to assess the presence/absence of other species of squirrel through the identification of the collected hairs. The objectives of this study were to characterize the hairs of the Red-Bellied Squirrel and to test the use of hair tubes to detect the presence of this species. The study was conducted in the province of Buenos Aires, Argentina, from January to July 2004. Hairs from the back, head and tail have dark and light stripes while hairs from the belly are uniformly reddish brown. A multi-seriated medullar pattern was observed in the hairs of the back, head and belly, while the tail’s hairs showed a different medullar pattern that can be described as overlapped dark rings. Cuticle scales patterns corresponded to the normal mosaic type in the hairs of the tail, back, head and belly, and for the last three regions a different pattern was observed next to the hair bulb. Hair tubes were made of PVC tubes (25 × 6 cm) opened at both extremes. The tubes had an adhesive tape attached at both extremes and bait (peanuts and nuts) was offered in the centre. Given the arboreal habits of this squirrel, traps were placed on tree branches and inspected weekly. The hair tubes were successful in collecting hairs of the Red-Bellied Squirrel that can be distinguished from those of other mammals inhabiting the same area. Because this is quite a simple and inexpensive technique, we consider it an appropriate method to evaluate the presence of this alien species in the region.