Short perceptual range and yet successful invasion of a fragmented landscape: The case of the red-bellied tree squirrel (Callosciurus erythraeus) in Argentina

Dispersal is a key element of the invasion process for introduced species, and is influenced by landscape connectivity. The red-bellied squirrel (Callosciurus erythraeus) was introduced to Argentina in 1970. Suitable forest habitat for this arboreal species is highly fragmented in a rural-urban matrix, but despite this, the squirrel population has spread. Squirrels disperse into new habitat patches using connective features such as forest corridors. They may also cross gaps but up to what extent is not known. Gap crossing success is influenced by perceptual range, which is the distance from which animals can perceive suitable habitat. Perceptual range has been previously estimated for vulnerable species, but not for introduced species. We used a model relating perceptual range to body mass to predict the perceptual range of the red-bellied tree squirrel in Argentina. We then tested our prediction of 202-221 m by releasing squirrels in an unfamiliar arable field at different distances (300, 200, 100 and 20 m) from woodland habitat. We assumed that if woodland could be perceived, squirrels would orientate toward it. We estimated perceptual range to be between 20 and 100 m, considerably lower than predicted. Our results indicate that squirrels can potentially cross small habitat gaps, but dispersal over greater distances lacking connectivity is less likely. Incorporating this information when modelling the spread of exotic squirrels in the Pampas Region can yield more accurate prediction of the invasion process and guide management practices to minimise their expansion. © 2012 Springer Science+Business Media B.V.Fil: Bridgman, Lucy J.. The University of Waikato; Nueva ZelandaFil: Benitez, Verónica Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Graña Grilli, Maricel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Mufato, Natalia. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Acosta, Daniela. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Guichon, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentin

Feeding habits of coypu (Myocastor coypus Molina 1978) in the wetlands of the Southern region of Brazil

The aim of this study was to determine the diet of coypu (Myocastor coypus) in two areas (Santa Isabel do Sul wetlands – Area 1, and Santa Marta Farm – Area 2) in the Southern region of Brazil, using microhistological analyses of feces. Twenty-four plant species were identified from collected feces samples. Among the identified species, nine are common in the animals’ diet in both areas; the presence of Oriza sativa was not detected in any of the samples. Among the identified species, 84% and 54% of the coypu’s diet from Areas 1 and 2, respectively, are aquatic plants. Poaceae family was most common, being found in 82% of the samples from both areas. Paspalum disthichum (Area 1) and Panicum tricholaenoides (Area 2) were the most frequent species on the coypu’s diet. The diet comparison for both areas indicates that feeding habits vary depending on the type of habitat, environmental conditions and food availability. The absence of rice in our analysis may be an indication for the preservation of native areas around watercourses, so as to prevent coypu from invading irrigated crops.O objetivo deste estudo foi determinar a dieta do ratão-dobanhado (Myocastor coypus), em duas regiões (áreas alagadas em Santa Isabel do Sul – área 1 e Fazenda Santa Marta – área 2), na região sul do Brasil, utilizando microhistological análises de fezes. Foram identificadas 24 espécies de plantas nas amostras de fezes coletadas. Entre as espécies identificadas, nove são comuns a dieta dos animais de ambas as áreas, não sendo detectada a presença de Oriza sativa em nenhuma das amostras. Entre as espécies identificadas, 84% e 54% da dieta do ratão-do-banhado, nas áreas 1 e 2 respectivamente, são plantas aquáticas. A família Poaceae foi a mais abundante, sendo encontrada em 82% das amostras de ambas as áreas. Paspalum disthichum (área 1) e Panicum tricholaenoides (área 2), foram as espécies mais frequentes na dieta do ratão-do-banhado. A comparação da dieta de ambas as áreas mostrou que a alimentação varia dependendo do tipo de habitat, condições ambientais e de disponibilidade alimentar. A ausência de arroz na nossa análise pode ser um indicativo de que a preservação de áreas nativas ao redor de cursos d’água, evita que o ratão-do-banhado utilize as culturas de arroz