Autor: Marcelo Bello

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.