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Atualmente a ordem Didelphimorphia apresenta uma única família, denominada Didelphidae, distribuída ao longo do continente americano (Emmons & Feer, 1997). No Brasil, são conhecidos pelo menos 15 gêneros e 65 espécies (Fonseca et al., 1996). Esse número ultrapassa 70 espécies quando considerada toda a Região Neotropical (Emmons & Feer, 1997). Os marsupiais neotropicais ocorrem desde as florestas austrais e habitats arbustivos da Patagônia, passando pelos Andes e toda extensão das florestas de planície subtropicais e tropicais, cerrados e chaco, até as regiões áridas de caatinga. Estendem-se ainda, representados por uma única espécie de gambá (Didelphis virginiana), até as regiões temperadas da América do Norte (Emmons & Feer, 1997). Os marsupiais didelfídeos ocupam uma grande variedade de nichos, sendo a maior parte dos gêneros de marsupiais neotropicais arborícolas ou ao menos escansoriais (Fonseca et al., 1996; Emmons & Feer, 1997). Podem ocupar um gradiente desde as espécies mais frugívoras, onívoras até as mais carnívoras (Santori & Astúa de Moraes, 2005). Essas diferenças entre as espécies nos nichos que ocupam podem permitir a coexistência de um maior número de espécies na comunidade, e devem implicar em especializações da morfologia diretamente ligadas à locomoção e à alimentação (Vieira, 2005). Estes marsupiais são remanescentes de um grupo ancestral da fauna de mamíferos terrestres que viveu durante a maior parte do Cenozóico, alcançando alta diversidade de espécies na América do Sul (Marshall & Cifelli, 1990). Os gambás e as cuícas neotropicais estão entre os mamíferos contemporâneos mais diversificados, sendo considerados um grupo de evolução mais recente (Mioceno) dentre os marsupiais (Oliveira & Goin, 2005). Os marsupiais atuais são mais arborícolas e onívoros, e isso pode ser atribuído à invasão de espécies de mamíferos placentários provenientes dos continentes do norte durante o Plioceno, o que foi chamado de 'Grande Intercâmbio Americano'. Essas espécies invasoras foram melhores competitivamente, conduzindo as espécies mais especializadas à extinção, entre elas alguns grandes marsupiais carnívoros, e colaborando para que as espécies mais arborícolas e/ou mais onívoras sobrevivessem (Webb & Rancy, 1996). Entre os gêneros conhecidos para a região neotropical, nove são compostos por espécies que usam o estrato arbóreo, mesmo que esporadicamente (Didelphis, Philander, Marmosa, Gracilinanus, Micoureus, Marmosops, Caluromys, Caluromysiops e Glironia), quatro usam exclusivamente o solo (Criptonanus, Thylamys, Monodelphis e Metachirus), ao passo que outros dois são associados a ambientes aquáticos (Lutreolina e Chironectes) (Fonseca et al., 1996; Emmons & Feer, 1997). Uma das vantagens que a vida arbórea traz é a possibilidade de se ter acesso a frutos antes que esses caiam e fiquem disponíveis no solo para outros organismos (Miranda & Passos, 2004). Para mamíferos não voadores, parece haver uma relação estreita entre a dieta do animal e o estrato vertical ocupado (Malcom, 1995; Vieira & Astúa de Moraes, 2003). Sendo assim, as espécies com maior atividade arbórea (e.g. Caluromys e Micoureus) seriam também aquelas para as quais os frutos são mais importantes na dieta (Charles Dominique, 1983; Santori & Astúa de Moraes, 2005). Devido à ampla distribuição geográfica dos marsupiais didelfídeos no Brasil, o conhecimento sobre ecologia dos membros desta família vem sendo acrescido também de informações sobre os hábitos alimentares. Os primeiros estudos no Brasil tiveram início na década de 40; contudo desde essa época até o momento, os mais variados estudos sobre dieta tratam de apenas uma pequena parcela dos marsupiais neotropicais, sendo que os biomas são pouco explorados em função de produção e disponibilidade de alimento aos marsupiais. O presente estudo aborda no primeiro capítulo, a dieta de Didelphis aurita, Micoureus paraguayanus e de Caluromys lanatus, e a relação da dieta como uso do estrato vertical e partição de recursos entre essas espécies. Após a caracterização das dietas, as relações entre disponibilidade de alimento no ambiente, amplitude alimentar e ciclo reprodutivo de D. aurita são tratados no segundo capítulo. Nestes dois capítulos, são enfocados também o oportunismo, a frugivoria e a capacidade de dispersão de sementes por estes animais. This study has the aim to analyse the diet of didelphid marsupials, namely the black-eared opossum Didelphis aurita, the woolly mouse opossum Micoureus paraguayanus and the western woolly opossum Caluromys lanatus, besides the effects of resource partitioning among these sympatric species, in a seasonal forest of southern Brazil. For this purpose, 100 live traps were set in the forest canopy (20 m apart; above 10 m in height) and other 50 (40 m apart) on the ground from August 2004 to July 2005. Species of opossums captured were identified and separated by sex, age and by their reproductive condition in order to compare diets among these classes. Their faeces were collected on the trap floor and analyzed after being washed with a 1 mm mesh. After 8,500 trap-nights, 41 faecal samples of D. aurita, eight of M. paraguayanus and two of C. lanatus were sampled. The three species of opossum studied were heterogeneous in relation to thein diet composition, being significantly different from each other. When compared, individuals of D. aurita trapped in the canopy vs. those trapped in the floor level, or even regarding age and sex classes, did not differ in diet composition. Nevertheless, all individuals of D. aurita trapped at the canopy were young, which corroborates an observed trend to young have a larger dietary niche not a young canopy was captured while the ones on the floor were captured as young individuals as adult individuals. All species presented insects in their diets, but with a to consume fruits (both species) or vertebrates (D. aurita). Hence, D. aurita was more omnivorous, and M. paraguayanus, regarding its little faecal samples, revealed several fruit species in their diet, such as Cecropia pachystachia and Piper sp. The role of these marsupials as opportunistic consumers as well as the role of body size and habitat differences determining trends in diet are discussed.Seasonal forests have marked periods of rains and drought, and animals living there are thought to be adapted to this condition. This study aims to obtain information about relationships between availability of food resources (fruits) and biotic parameters of didelphid marsupials, such as reproduction level and fruit consumption, in a seasonal semideciduous forest of southern Brazil. This study was developed with Micoureus paraguayanus and Didelphis aurita, focusing mainly the similarities in the rhythms of consumption rather than their main differences in foraging. For this purpose, 100 live traps were set in the forest canopy (20 m apart; above 10 m in height) and other 50 (40 m apart) on the ground from August 2004 to July 2005. Their faeces were collected on a trap floor and seeds from them were identified and counted. The fruit availability in the area was quantified monthly through the collection of flesh fruits and flowers available on the ground, at 10 transect lines of 1 m in width. Because fruits of Piper do not detach usually from stems, this shrub species was sampled by counting fruiting individuals in the same 10 transect lines. Results were analyzed based on 33 faecal samples of D. aurita and eight of M. paraguayanus. Regarding fruits, diversity indexes of Shannon observed for the environment and for the marsupials species usually matched, being higher during the rainy months (November to March). Hence, rhythms of fructification of Piper sp. correlated to their consumption by marsupials (rs = 1.00, P = 0.04, for D. aurita and rs = 0.40, P = 0.60, for M. paraguayanus). There were trends to the major proportion of independent young and lactant females of D. aurita correlate to the peaks of fruit availability in the environment, mainly in November and January. Thus, the availability of resources had an important role in the reproduction and foraging behavior of the marsupial species. Marsupials are also adapted to reproduce and release young during favourable times, which matched with the warmer and rainy season at the seasonal semideciduous forest of southern Brazil.

We collected small mammals in two hydrographic basins in central Brazil, namely the Paraná and Araguaia basins, with the aim of examining the composition of forest dwelling small mammal species and to compare their geographic distributions. Fourteen sites were sampled, eight in the Paraná basin and six in the Araguaia basin. A total of 20 species of small mammals was registered (8 marsupials and 12 rodents), 16 of them in live traps (5,253 trap-nights) and eight in pitfalls (224 trap-nights), adding to a total of 161 captures of 139 individuals. The Paraná basin showed 16 species (trap-nights: 3,115 and 104 respectively) and the Araguaia basin 11 species (trap-nights: 2,138 and 120 respectively), being both richness similar when the rarefaction method was applied. Seven (35%) out of the 20 species recorded occurred in both basins. The marsupial Didelphis albiventris Lund, 1840 was the most abundant species. The marsupials species recorded were D. albiventris, Caluromys philander (Linnaeus, 1758), Cryptonanus cf. agricolai Voss, Lunde & Jansa, 2005, Gracilinanus agilis (Burmeister, 1854), G. microtarsus (Wagner, 1842), Lutreolina crassicaudata (Desmarest, 1804), Marmosa murina (Linnaeus, 1758), and Philander opossum (Linnaeus, 1758). The rodent species recorded were Akodon gr. cursor, Calomys tener (Winge, 1887), Nectomys rattus (Pelzen, 1883), N. squamipes (Brants, 1827), Oecomys bicolor (Tomes, 1860), Oryzomys maracajuensis Langguth & Bonvicino, 2002, Oryzomys cf. marinhus, O. megacephalus (Fischer, 1814), Oligoryzomys fornesi (Massoia, 1973), Oligoryzomys sp., Proechimys longicaudatus (Rengger, 1830) and P. roberti (Thomas, 1901). The range extension of some species is discussed, in addition to biogeographic considerations. The Caiapós Mountains may have been a geographic barrier for some small mammal species in the face of the retraction and expansion of forests in the past.