Helminth community structure of Didelphis marsupialis (Didelphimorphia, Didelphidae) in a transition area between the Brazilian Amazon and the Cerrado / Estrutura da comunidade de helmintos de Didelphis marsupialis (Didelphimorphia, Didelphidae) em uma área de transição entre a Amazônia brasileira e o Cerrado

Although the common opossum, Didelphis marsupialis (Didelphimorphia: Didelphidae) is a species widely distributed in South America, knowledge about their helminth parasites and helminth community structure is scarce. The aims of this study were to describe the species composition and analyze the structure of the helminth community of the common opossum in an area of the Amazonian Arc in northern Mato Grosso. The helminths were recovered, counted, and identified in 32 individuals. Overall, 10,198 specimens were categorized into 9 helminths taxa (seven nematodes, one cestode, and one acanthocephalan). The most abundant species were Aspidodera raillieti, Viannaia hamata, and Travassostrongylus orloffi. No statistically significant differences in helminth abundance and prevalence were observed between host sexes. However, young hosts had higher abundance and prevalence of Didelphonema longispiculata, whereas Oligacanthorhynchus microcephalus had higher abundance and prevalence in adult hosts. This was the first study to analyze the helminth fauna and helminth community structure of D. marsupialis in the Amazonian Arc. This is the first report of the presence of A. raillieti, D. longispiculata, T. orloffi, T. minuta, V. hamata, and O. microcephalus in the state of Mato Grosso, Brazil.(AU)

Embora o gambá comum, Didelphis marsupialis (Didelphimorphia: Didelphidae) seja uma espécie amplamente distribuída na América do Sul, o conhecimento sobre seus helmintos parasitos e a estrutura da comunidade de helmintos são escassos. Os objetivos deste estudo foram descrever a composição de espécies e analisar a estrutura da comunidade helmíntica do gambá comum em uma área do Arco Amazônico, no norte de Mato Grosso. Os helmintos foram recuperados, contados e identificados em 32 indivíduos. Ao todo, 10.198 espécimes foram categorizados em 9 táxons de helmintos (sete nematoides, um cestoide e um acantocéfalo). As espécies mais abundantes foram Aspidodera raillieti, Viannaia hamata e Travassostrongylus orloffi. Não foram observadas diferenças estatisticamente significativas na abundância e prevalência de helmintos entre os sexos dos hospedeiros. No entanto, hospedeiros jovens apresentaram maior abundância e prevalência de Didelphonema longispiculata, enquanto Oligacanthorhynchus microcephalus apresentou maior abundância e prevalência em hospedeiros adultos. Este foi o primeiro estudo a analisar a helmintofauna e a estrutura da comunidade helmíntica de D. marsupialis no Arco Amazônico. Este é o primeiro relato da presença de A. raillieti, D. longispiculata, T. orloffi, T. minuta, V. hamata e O. microcephalus no estado de Mato Grosso, Brasil.(AU)

First study on the helminth community structure of the neotropical marsupial Metachirus myosuros (Didelphimorphia, Didelphidae) / Primeiro estudo sobre a estrutura da comunidade de helmintos do marsupial neotropical Metachirus myosuros (Didelphimorphia, Didelphidae)

Metachirus myosuros is a marsupial species widely distributed in South America. Despite this, there is a lack of knowledge about its helminth parasites and helminth community structure. The aims of this study were to describe the species composition and determine the parasitological parameters of helminth communities of M. myosuros in preserved areas of the Atlantic Forest, Igrapiúna, Bahia state, northeastern Brazil. Parasites were searched from 19 specimens of this marsupial (18 were infected with at least one species), counted and identified. Ten species of helminth parasites were obtained: 7 nematodes, 2 platyhelminths and 1 acanthocephalan. The most abundant species were Aspidodera raillieti, Cruzia tentaculata, Physaloptera mirandai and Viannaia conspicua (Nematoda). These species were also the only dominant ones in the component community. Male hosts had higher prevalence of P. mirandai and greater abundance of V. conspicua. We observed a relationship between host body size and helminth abundance in both male and female hosts, and between host body size and helminth species richness in female hosts. This was the first study to analyze the helminth fauna and helminth community structure of M. myosuros. This was the first report of occurrences of A. raillieti and Didelphonema longispiculata in M. myosuros.(AU)

Metachirus myosuros é uma espécie de marsupial amplamente distribuída na América do Sul. Apesar disso, existe pouca informação sobre seus helmintos parasitos e estrutura da comunidade de helmintos. Os objetivos deste estudo foram descrever a composição e determinar os parâmetros parasitológicos em comunidades de helmintos de M. myosuros, em áreas preservadas de Mata Atlântica, Igrapiúna, Bahia, Nordeste do Brasil. Os parasitos foram procurados em 19 espécimes desse marsupial (18 estavam infectados com pelo menos uma espécie), contados e identificados. Dez espécies de helmintos foram coletadas: 7 nematoides, 2 platelmintos e 1 acantocéfalo. As espécies mais abundantes foram Aspidodera raillieti, Cruzia tentaculata, Physaloptera mirandai e Viannaia conspicua (Nematoda). Estas espécies também foram as únicas dominantes na comunidade componente. Os hospedeiros machos tiveram maior prevalência de P. mirandai e maior abundância de V. conspicua. Foi observada uma relação significativa entre o tamanho do corpo do hospedeiro e a abundância de helmintos em hospedeiros machos e fêmeas, e entre o tamanho do corpo do hospedeiro e a riqueza de espécies de helmintos em fêmeas. Este foi o primeiro estudo a analisar a helmintofauna e a estrutura da comunidade de helmintos de M. myosuros. E também foi o primeiro relato da ocorrência de A. raillieti e Didelphonema longispiculata em M. myosuros.(AU)

First report of the intestinal helminth community in the broad-headed spiny-rat Clyomys laticeps (Rodentia, Echimyidae) / Primeiro registro da comunidade de helmintos intestinais do rato de espinho Clyomys laticeps (Rodentia, Echymyidae)

The broad-headed spiny rat, Clyomys laticeps, is an echimyid rodent found in open areas of Cerrado and Pantanal biomes in central Brazil and Paraguay. Little is known about the parasites associated with this semi-fossorial species, as no previous studies have been conducted on their helminth fauna. The aim of this study was to report the helminth community structure of C. laticeps inhabiting Serra de Caldas Novas State Park, a Cerrado area in central Brazil. Trappings were carried out in dry grasslands from January to October 2016, and the large and small intestines of 14 C. laticeps individuals were examined for the presence of helminths. Three nematode species were found: Fuellebornema almeidai, Pterygodermatites (Paucipectines) sp., and Subulura forcipata, and 85.7% of the studied species were infected with at least one of these helminths. F. almeidai was the most prevalent species among hosts, and S. forcipata was the most abundant. This study is the first report on helminth community structure in C. laticeps. We report a new host species and increase the known geographical range of F. almeidai, and provide the first record of Pterygodermatites (Paucipectines) sp. infecting echimyids. This is also the first report of S. forcipata in a mammal host.(AU)

Clyomys laticeps é um roedor equimídeo encontrado em áreas abertas dos biomas Cerrado e Pantanal, ao longo do Brasil central e Paraguai. Essa espécie apresenta hábitos semi-fossoriais e atividade noturna. Até o momento, não existem estudos sobre seus parasitas. O objetivo deste trabalho foi descrever a comunidade de helmintos encontrados em C. laticeps, capturados no Parque Estadual da Serra de Caldas Novas, uma área de Cerrado no Brasil Central. Os indivíduos foram capturados em área de campo sujo entre janeiro e outubro de 2016. Os intestinos delgado e grosso de 14 roedores foram examinados quanto à presença de helmintos. Três espécies de nematoides foram encontradas: Fuellebornema almeidai, Pterygodermatites (Paucipectines) sp. e Subulura forcipata. Considerando-se as três espécies, 85,7% dos roedores apresentaram pelo menos um helminto. F. almeidai foi a espécie mais prevalente, enquanto Subulura forcipata foi a mais abundante. Este estudo é o primeiro registro da estrutura da comunidade de helmintos para C. laticeps. Como resultado, foi registrado um novo hospedeiro e o aumento da área de distribuição geográfica para o nematódeo F. almeidai e o primeiro caso de Pterygodermatites (Paucipectines) sp. infectando um roedor equimídeo. Além disso, este estudo também traz o primeiro registro de S. forcipata infectando um mamífero.(AU)

Community structure and population dynamics of small mammals in an urban-sylvatic interface area in Rio de Janeiro, Brazil

The Atlantic Forest is one of the most disturbed Brazilian biomes, with 183 out of 298 species of mammals occurring in the state of Rio de Janeiro. In this study, we aimed to characterize the diversity, community structure, and habitat use of small mammals in the FIOCRUZ Atlantic Forest Campus (CFMA), including areas of Pedra Branca State Park (PBSP, subunit Pau da Fome), state of Rio de Janeiro. We also compared species diversity and composition between two moments 15 years apart (2001 and 2012-2015) and analyzed the population dynamics of the marsupial Didelphis aurita (Wied-Neuwied, 1826). Small mammal captures were made in different habitats: sylvatic-urban interface areas near human dwellings, disturbed forest, and preserved forest areas. Five marsupial species and four rodent species were captured in both periods. There was a reduction in species richness and β diversity between the two periods, indicating that disturbances in the environment over the years may have affected the small mammal community structure. The most altered environment showed the greatest species richness and abundance, while the forest areas showed the smallest values, which may be explained by the loss of mammal species, mainly specialist species in forested areas. We identified three groups of species according to habitat preferences: one related to environments with a higher density of vegetation in upper strata - Marmosa paraguayana (Tate, 1931) and Monodelphis americana (Müller, 1776), another related to a higher density in lower forest strata - Akodon cursor (Winge, 1887), and another with no association with the investigated habitat variables - D. aurita and Oligoryzomys nigripes (Olfers, 1818). The small mammal community structure showed a low level of nestedness in both sampling periods.[...](AU)

Community structure and population dynamics of small mammals in an urban-sylvatic interface area in Rio de Janeiro, Brazil

The Atlantic Forest is one of the most disturbed Brazilian biomes, with 183 out of 298 species of mammals occurring in the state of Rio de Janeiro. In this study, we aimed to characterize the diversity, community structure, and habitat use of small mammals in the FIOCRUZ Atlantic Forest Campus (CFMA), including areas of Pedra Branca State Park (PBSP, subunit Pau da Fome), state of Rio de Janeiro. We also compared species diversity and composition between two moments 15 years apart (2001 and 2012-2015) and analyzed the population dynamics of the marsupial Didelphis aurita (Wied-Neuwied, 1826). Small mammal captures were made in different habitats: sylvatic-urban interface areas near human dwellings, disturbed forest, and preserved forest areas. Five marsupial species and four rodent species were captured in both periods. There was a reduction in species richness and β diversity between the two periods, indicating that disturbances in the environment over the years may have affected the small mammal community structure. The most altered environment showed the greatest species richness and abundance, while the forest areas showed the smallest values, which may be explained by the loss of mammal species, mainly specialist species in forested areas. We identified three groups of species according to habitat preferences: one related to environments with a higher density of vegetation in upper strata - Marmosa paraguayana (Tate, 1931) and Monodelphis americana (Müller, 1776), another related to a higher density in lower forest strata - Akodon cursor (Winge, 1887), and another with no association with the investigated habitat variables - D. aurita and Oligoryzomys nigripes (Olfers, 1818). The small mammal community structure showed a low level of nestedness in both sampling periods.[...]

Ticks parasitizing wild mammals in Atlantic Forest areas in the state of Rio de Janeiro, Brazil / Carrapatos parasitando mamíferos silvestres em áreas da Floresta Atlântica no estado do Rio de Janeiro, Brasil

Mammals captured in the Serra dos Órgãos National Park (PARNASO) and the Pedra Branca State Park (PBSP) between 2012 and 2015 were examined for the presence of ticks. In total, 140 mammals were examined, and 34 specimens were found to be parasitized by ticks. Didelphis aurita, Akodon montensis and Oligoryzomys nigripes were the species most parasitized. From these specimens, 146 ticks were collected, including 10 larvae. The ticks belonged to eight species: one in the genus Ixodes and seven in the genus Amblyomma. This study reports new associations of ticks and wild mammals in Brazil.(AU)

Mamíferos capturados no Parque Nacional da Serra dos Órgãos (PARNASO) e no Parque Estadual Pedra Branca (PBSP) entre 2012 e 2015 foram examinados quanto à presença de carrapatos. No total, 140 mamíferos foram examinados, e 34 espécimes foram parasitados por carrapatos. Didelphis aurita, Akodon montensis e Oligoryzomys nigripes foram as espécies mais parasitadas. A partir desses espécimes, 146 carrapatos foram coletados, incluindo 10 larvas. Os carrapatos pertenciam a oito espécies: uma no gênero Ixodes e sete no gênero Amblyomma. Este estudo relata novas associações de carrapatos e mamíferos silvestres no Brasil.(AU)

Helminth metacommunity structure of wild rodents in a preserved area of the Atlantic Forest, Southeast Brazil / Estrutura da metacomunidade de helmintos de roedores silvestres em uma área preservada da Floresta Atlântica, sudeste do Brasil

The helminth fauna and metacommunity structure of eight sympatric sigmodontine rodents were investigated at the Serra dos Órgãos National Park, an Atlantic Forest reserve located in the State of Rio de Janeiro, southeast Brazil. Rodents of the species Abrawayaomys ruschii, Akodon montensis, Blarinomys breviceps , Delomys dorsalis, Oligoryzomys flavescens, Oligoryzomys nigripes, Oxymycterus quaestor and Thaptomys nigrita were found infected with helminths. Akodon montensis presented the highest total helminth species richness, with six different species of helminths. The nematode Stilestrongylus lanfrediae was the most abundant and prevalent helminth species observed. The host-parasite network analysis showed little interactions among host species. Akodon montensis seems to act as a keystone-species in the rodent community. This species shared the nematodes Stilestrongylus aculeata with A. ruschii and Protospirura numidica criceticola with T. nigrita, and the cestode Rodentolepis akodontis with D. dorsalis. The congeners host species O. flavescens and O. nigripes shared the nematodes Guerrerostrongylus zetta and S. lanfrediae. The rodents B. breviceps and O. quaestor did not share any helminths with other hosts. The helminth metacommunity showed a random pattern on both infracommunity and component community levels, indicating different responses by each helminth species to the environmental gradient.(AU)

Foram investigadas a helmintofauna e suas estruturas da metacomunidade em oito roedores sigmodontíneos simpátricos ao longo do Parque Nacional da Serra dos Órgãos, uma reserva de Mata Atlântica no estado do Rio de Janeiro, Brasil. Roedores das espécies Abrawayaomys ruschii, Akodon montensis, Blarinomys breviceps, Delomys dorsalis, Oligoryzomys flavescens, Oligoryzomys nigripes, Oxymycterus quaestor e Thaptomys nigrita foram infectados por helmintos. Akodon montensis apresentou a maior riqueza total de espécies de helmintos, com seis espécies. O nematoide Stilestrongylus lanfrediae foi a espécie de helminto com maior abundância e prevalência. A análise de rede parasito-hospedeiro mostrou poucas interações entre as espécies hospedeiras e A. montensis atuou como uma espécie-chave na comunidade de roedores. Esta espécie compartilhou os nematoides Stilestrongylus aculeata com A. ruschii e Protospirura numidica criceticola com T. nigrita, e o cestoide Rodentolepis akodontis com D. dorsalis. As espécies congêneres O. flavescens e O. nigripes compartilharam os nematoides Guerrerostrongylus zetta e S. lanfrediae. Os roedores B. breviceps e O. quaestor não compartilharam helmintos com outros hospedeiros. A metacomunidade de helmintos mostrou um padrão aleatório em ambos os níveis, comunidade componente e infracomunidade, indicando diferentes respostas de cada espécie de helminto ao gradiente ambiental.(AU)

A comparison of abundance estimators for small mammal populations

A major difficulty in the application of probabilistic models to estimations of mammal abundance is obtaining a data set that meets all of the assumptions of the model. In this paper, we evaluated the concordance correlation among three population size estimators, the minimum number alive (MNA), jackknife and the model suggested by the selection algorithm in CAPTURE (the best-fit model), using long-term data on three Brazilian small mammal species obtained from three different studies. The concordance correlation coefficients between the abundance estimates indicated that the probabilistic and enumeration estimators were highly correlated, giving concordant population estimates, except for one species in one of the studies. The results indicate the adequacy of using enumeration estimates as indexes for population size when scarce data do not allow for the use of probabilistic methods. Differences observed in the behavior of enumeration and probabilistic methods among species and studies can be related to the exclusive sampling design of each area, species-specific movement characteristics and whether a significant portion of the population could be sampled.

Biochemical and histological changes in liver of Nectomys squamipes naturally infected by Schistosoma mansoni / Alterações na bioquímica e histologia do fígado de Nectomys squamipes naturalmente infectado por Schistosoma mansoni

The South American water rat Nectomys squamipes is a wild mammal reservoir of Schistosoma mansoni in Brazil. In the present study, wild rodents were collected in the field and categorized into two groups: infected and uninfected by S. mansoni. Blood was collected to analyze changes in the serum glucose level (mg/dL) and liver fragments were used to determine the hepatic glycogen content (mg of glucose/g tissue). The histological examination showed inflammatory granulomatous lesions in different phases of development in the liver of rodents naturally infected with S. mansoni, in some cases with total or partial occlusion of the vascular lumen. Early lesions were characterized by the presence of inflammatory infiltrate around morphologically intact recently deposited eggs. Despite the significance of these histological lesions, the biochemical changes differed in extent. N. squamipes naturally infected by S. mansoni showed no variation in hepatic glycogen reserves. These findings were accompanied by a significant increase in plasma glucose contents, probably as a consequence of amino acids deamination, which are degraded, resulting in the formation of intermediates used as precursors for the glucose formation, without compromising the reserves of liver glycogen. In the wild, naturally infected N. squamipes can maintain S. mansoni infections without undergoing alterations in its carbohydrate metabolism, which minimizes the deleterious effects of S. mansoni.

Nectomys squamipes é um mamífero silvestre reservatório de Schistosoma mansoni no Brasil. No presente estudo, os roedores silvestres, colhidos no campo, foram classificados em dois grupos: infectado e não infectado por S. mansoni. O sangue foi colhido para análise da alteração no nível de glicose sérico (mg/dL) e fragmentos de fígado foram usados para determinar o conteúdo de glicogênio hepático (mg de glicose/g tecido). A análise histológica demonstrou lesões granulomatosas em diferentes fases de desenvolvimento no tecido hepático dos roedores naturalmente infectados com S. mansoni, localizados principalmente na região periportal, com total ou parcial oclusão do lúmen vascular. As lesões foram caracterizadas por presença de infiltrado inflamatório ao redor de ovos morfologicamente intactos recentemente depositados. Apesar da grande significância das lesões histológicas, as alterações bioquímicas não diferiram no mesmo grau. N. squamipes naturalmente por S. mansoni não apresentaram variação na reserva de glicogênio hepático. Esses achados foram acompanhados pelo aumento significativo nos conteúdos de glicose plasmática, provavelmente como consequência ao processo desaminativo de aminoácidos, que passam a ser degradados notadamente para a formação de glucose, sem contudo comprometer a reserva de glicogênio hepático. Em condições naturais a infecção de S. mansoni pode ser mantida usando N. squamipes como hospedeiro definitivo, sem alterações significativas nos conteúdos de glicogênio hepático, minimizando os efeitos deletérios causados por S. mansoni nos roedores N. squamipes naturalmente infectados.

Biochemical and histological changes in liver of Nectomys squamipes naturally infected by Schistosoma mansoni

The South American water rat Nectomys squamipes is a wild mammal reservoir of Schistosoma mansoni in Brazil. In the present study, wild rodents were collected in the field and categorized into two groups: infected and uninfected by S. mansoni. Blood was collected to analyze changes in the serum glucose level (mg/dL) and liver fragments were used to determine the hepatic glycogen content (mg of glucose/g tissue). The histological examination showed inflammatory granulomatous lesions in different phases of development in the liver of rodents naturally infected with S. mansoni, in some cases with total or partial occlusion of the vascular lumen. Early lesions were characterized by the presence of inflammatory infiltrate around morphologically intact recently deposited eggs. Despite the significance of these histological lesions, the biochemical changes differed in extent. N. squamipes naturally infected by S. mansoni showed no variation in hepatic glycogen reserves. These findings were accompanied by a significant increase in plasma glucose contents, probably as a consequence of amino acids deamination, which are degraded, resulting in the formation of intermediates used as precursors for the glucose formation, without compromising the reserves of liver glycogen. In the wild, naturally infected N. squamipes can maintain S. mansoni infections without undergoing alterations in its carbohydrate metabolism, which minimizes the deleterious effects of S. mansoni.

Nectomys squamipes é um mamífero silvestre reservatório de Schistosoma mansoni no Brasil. No presente estudo, os roedores silvestres, colhidos no campo, foram classificados em dois grupos: infectado e não infectado por S. mansoni. O sangue foi colhido para análise da alteração no nível de glicose sérico (mg/dL) e fragmentos de fígado foram usados para determinar o conteúdo de glicogênio hepático (mg de glicose/g tecido). A análise histológica demonstrou lesões granulomatosas em diferentes fases de desenvolvimento no tecido hepático dos roedores naturalmente infectados com S. mansoni, localizados principalmente na região periportal, com total ou parcial oclusão do lúmen vascular. As lesões foram caracterizadas por presença de infiltrado inflamatório ao redor de ovos morfologicamente intactos recentemente depositados. Apesar da grande significância das lesões histológicas, as alterações bioquímicas não diferiram no mesmo grau. N. squamipes naturalmente por S. mansoni não apresentaram variação na reserva de glicogênio hepático. Esses achados foram acompanhados pelo aumento significativo nos conteúdos de glicose plasmática, provavelmente como consequência ao processo desaminativo de aminoácidos, que passam a ser degradados notadamente para a formação de glucose, sem contudo comprometer a reserva de glicogênio hepático. Em condições naturais a infecção de S. mansoni pode ser mantida usando N. squamipes como hospedeiro definitivo, sem alterações significativas nos conteúdos de glicogênio hepático, minimizando os efeitos deletérios causados por S. mansoni nos roedores N. squamipes naturalmente infectados.

Population ecology of small rodents and marsupials in a semi-deciduous tropical forest of the southeast Pantanal, Brazil

The Pantanal is a South American biome characterized by extensive plains and stark environmental seasonality. Several habitats are subject to annual flooding, forcing small mammal species to aggregate in dry forest patches, which most likely influences their population dynamics and life history strategies. In order to investigate the seasonal influence on the life history traits of these small mammals, we conducted a 2-year mark-recapture study in the southeastern region of the Brazilian Pantanal (Nhecolândia) and analyzed the population dynamics of the most abundant small mammal species with the jackknife estimator. A trapping effort of 21,560 trap-nights resulted in 615 individuals in 1,171 captures (success = 5.43%). Three species of rodents - Oecomys mamorae (Thomas, 1906), Thrichomys pachyurus (Wagner, 1845), and Clyomys laticeps (Thomas, 1841) - and three species of marsupials - Gracilinanus agilis (Burmeister, 1854), Thylamys macrurus (Olfers, 1818), and Monodelphis domestica (Wagner, 1842) - were obtained. The most abundant species was O. mamorae, followed by G. agilis and T. pachyurus. Oecomys mamorae was more abundant in the wet season and presented an opportunistic reproductive strategy. Gracilianus agilis displayed increased population sizes in the dry season and synchronized, seasonal reproduction during the rainy season. Thrichomys pachyurus had a small population size, delayed response to variations in environmental conditions and higher reproductive rates in the dry season. All species revealed different life history strategies (seasonal, opportunistic or delayed response to environmental variations), coinciding with periods of higher resource availability in order to maximize survival.

Population ecology of small rodents and marsupials in a semi-deciduous tropical forest of the southeast Pantanal, Brazil

The Pantanal is a South American biome characterized by extensive plains and stark environmental seasonality. Several habitats are subject to annual flooding, forcing small mammal species to aggregate in dry forest patches, which most likely influences their population dynamics and life history strategies. In order to investigate the seasonal influence on the life history traits of these small mammals, we conducted a 2-year mark-recapture study in the southeastern region of the Brazilian Pantanal (Nhecolândia) and analyzed the population dynamics of the most abundant small mammal species with the jackknife estimator. A trapping effort of 21,560 trap-nights resulted in 615 individuals in 1,171 captures (success = 5.43%). Three species of rodents - Oecomys mamorae (Thomas, 1906), Thrichomys pachyurus (Wagner, 1845), and Clyomys laticeps (Thomas, 1841) - and three species of marsupials - Gracilinanus agilis (Burmeister, 1854), Thylamys macrurus (Olfers, 1818), and Monodelphis domestica (Wagner, 1842) - were obtained. The most abundant species was O. mamorae, followed by G. agilis and T. pachyurus. Oecomys mamorae was more abundant in the wet season and presented an opportunistic reproductive strategy. Gracilianus agilis displayed increased population sizes in the dry season and synchronized, seasonal reproduction during the rainy season. Thrichomys pachyurus had a small population size, delayed response to variations in environmental conditions and higher reproductive rates in the dry season. All species revealed different life history strategies (seasonal, opportunistic or delayed response to environmental variations), coinciding with periods of higher resource availability in order to maximize survival.

Population ecology of small rodents and marsupials in a semi-deciduous tropical forest of the southeast Pantanal, Brazil

The Pantanal is a South American biome characterized by extensive plains and stark environmental seasonality. Several habitats are subject to annual flooding, forcing small mammal species to aggregate in dry forest patches, which most likely influences their population dynamics and life history strategies. In order to investigate the seasonal influence on the life history traits of these small mammals, we conducted a 2-year mark-recapture study in the southeastern region of the Brazilian Pantanal (Nhecolândia) and analyzed the population dynamics of the most abundant small mammal species with the jackknife estimator. A trapping effort of 21,560 trap-nights resulted in 615 individuals in 1,171 captures (success = 5.43%). Three species of rodents - Oecomys mamorae (Thomas, 1906), Thrichomys pachyurus (Wagner, 1845), and Clyomys laticeps (Thomas, 1841) - and three species of marsupials - Gracilinanus agilis (Burmeister, 1854), Thylamys macrurus (Olfers, 1818), and Monodelphis domestica (Wagner, 1842) - were obtained. The most abundant species was O. mamorae, followed by G. agilis and T. pachyurus. Oecomys mamorae was more abundant in the wet season and presented an opportunistic reproductive strategy. Gracilianus agilis displayed increased population sizes in the dry season and synchronized, seasonal reproduction during the rainy season. Thrichomys pachyurus had a small population size, delayed response to variations in environmental conditions and higher reproductive rates in the dry season. All species revealed different life history strategies (seasonal, opportunistic or delayed response to environmental variations), coinciding with periods of higher resource availability in order to maximize survival.