Small mammals can be used as environmental indicators and have been intensively studied in fragmented landscapes of Atlantic Forest, with a wide range of field methods. Our aim in this study was two-fold: we tested for the effects of methods and for the effects of the main environmental variables on observed small mammal richness in fragments of Atlantic Forest. We gathered information on small mammal richness, methods and environmental variables from 122 fragments of Atlantic Forest through literature review. These data were analysed using linear models and model selection based on AIC values along with a regression tree analysis. We found that studies will record more species with bigger trapping effort, using pitfall traps and sampling all forest strata. We also confirmed two important ecological assumptions: fragments at lower latitudes and bigger fragments were the ones with higher species richness. Methodological and environmental variables were analysed together on a regression tree, where trapping effort was the most important variable, surpassing any environmental effect. Considering that a significant number of the studies on Atlantic Forest fragments did not use pitfall traps or sample all forest strata, their results on forest fragmentation were affected by sampling bias.
Natural resources are depleted in fragmented landscapes that have their vegetation also altered. As a result, the microhabitat diversity and the composition and distribution of local species are affected. In this study, we evaluated the small mammals' community diversity, composition and microhabitat selection in two Atlantic Forest fragments, in an ecotone area with the Pampa biome, southern Brazil. We recorded five rodents (Akodon montensis, Oligoryzomys nigripes, Sooretamys angouya, Juliomys pictipes and the exotic Rattus rattus) and one marsupial (Didelphis albiventris). Both fragments were dominated by the generalist rodent A. montensis. Akodon montensis and O. nigripes showed similar habitat preferences: ground covered by rocks and higher values of vegetation obstruction. Sooretamys angouya preferred places with higher abundance of trees. Fruit availability was important for A. montensis and D. albiventris, highlighting the importance of this food resource for local wildlife, and the potential role of these species as seed predators and dispersers. Small species richness, the presence of an exotic species and high dominance level suggest that the study area is highly degraded.
Animal movement has an important role in individual performance, species reproduction, population demography, and conservation, especially in fragmented landscapes. The distance moved by an individual may vary depending on individual needs, such as the search for food resources and sexual partners. Here we investigated which factors affect the distances between successive captures (hereafter DSC) for Akodon montensis, Oligoryzomys nigripes, Sooretamys angouya, and Didelphis albiventris. This study was conducted from April 2015 to October 2016 in two fragments in the south of Atlantic Forest biome through capture, mark and recapture technique. DSC was analyzed using Generalized Linear Models with Poisson distribution where the independent variables were sex, whether the animal was active or not in terms of reproduction, body weight, and climatic season. The mean DSC was greater for D. albiventris (44.6 ± 28.8 m), followed by S. angouya (31.9 ± 25.7 m), O. nigripes (25.8 ± 22.5 m) and A. montensis (18.9 ± 22.0 m). Males of all species moved larger DSC than females. Considering the rodents, reproductive animals also moved larger DSC than non-reproductive animals. Sex may have masked the effect of body weight, as males tend to be larger than females. Climatic effects were tested for A. montensis and O. nigripes, however, with diverse effects.
Oligoryzomys nigripes is a generalist rodent widely distributed in South America. The present study aims to present information on abundance, reproduction, and litter size for O. nigripes in the south of Atlantic Forest biome. This study was conducted at two forest fragments in Cerro Largo, RS, between April 2015 and October 2016, with 5,320 trap-nights. We captured most of the individuals captured during winter and spring, corroborating previous researches that indicated higher abundance during the coldest months on the southern portion of O. nigripes distribution. Reproductive animals were found during all seasons, however, males had greater chances to be reproductive during spring. During autumn of 2015, through handling and identification, one reproductive female had three young; this was a rare record of litter size for a Neotropical rodent.
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