Differential success in sampling of Atlantic Forest amphibians among different periods of the day.

In general, anurans tend to be nocturnal, though diurnal activity is characteristic of some groups. Studies show that frog activity may be inferred based on the number of individuals collected at different periods of the day, during large-scale field surveys. We investigated the best period of the day to conduct amphibian sampling in nine Atlantic Rainforest areas in southeastern Brazil, based on intensive field surveys. At each locality we employed similar sampling effort during diurnal, crepuscular and nocturnal searches (totaling 704.5 sampling hours). We pooled data from all localities for each period and estimated the proportion of frogs of each species active at each period based on the total number of individuals and on the number of species found during all surveys for that period. We recorded a total of 817 individual frogs from 69 species. Species richness was highest at night (median = 12 species), intermediate at dusk (median = 8), and lowest during the day (median = 4). The percentage of the total number of individual frogs found (pooled species) was highest during the night (ca. 53%) and lowest during the day (ca. 14%). Analyzing each species separately, the number of individuals recorded was consistently higher at dusk and night for most species. Our study evidences a trend for nocturnal activity for most Atlantic Rainforest frogs, with few species having primarily diurnal habits. Those results may favor future studies and conservation efforts for amphibian species.

Differential success in sampling of Atlantic Forest amphibians among different periods of the day / Sucesso diferenciado na amostragem de anfíbios da Mata Atlântica entre diferentes períodos do dia

In general, anurans tend to be nocturnal, though diurnal activity is characteristic of some groups. Studies show that frog activity may be inferred based on the number of individuals collected at different periods of the day, during large-scale field surveys. We investigated the best period of the day to conduct amphibian sampling in nine Atlantic Rainforest areas in southeastern Brazil, based on intensive field surveys. At each locality we employed similar sampling effort during diurnal, crepuscular and nocturnal searches (totaling 704.5 sampling hours). We pooled data from all localities for each period and estimated the proportion of frogs of each species active at each period based on the total number of individuals and on the number of species found during all surveys for that period. We recorded a total of 817 individual frogs from 69 species. Species richness was highest at night (median = 12 species), intermediate at dusk (median = 8), and lowest during the day (median = 4). The percentage of the total number of individual frogs found (pooled species) was highest during the night (ca. 53%) and lowest during the day (ca. 14%). Analyzing each species separately, the number of individuals recorded was consistently higher at dusk and night for most species. Our study evidences a trend for nocturnal activity for most Atlantic Rainforest frogs, with few species having primarily diurnal habits. Those results may favor future studies and conservation efforts for amphibian species.(AU)

Em geral, anuros tendem a ser noturnos, apesar de a atividade diurna ser característica de alguns grupos. Estudos mostram que a atividade de anuros pode ser inferida com base no número de indivíduos coletados em diferentes períodos do dia durante pesquisas de campo de larga escala. Nós avaliamos qual o melhor período do dia para conduzir amostragens de anfíbios em nove áreas da Mata Atlântica no sudeste do Brasil, com base em amostragens de campo intensivas. Em cada localidade nós empregamos esforço de amostragem similar durante amostragens diurnas, crepusculares e noturnas (totalizando 704,5 horas de amostragem). Nós agrupamos dados de todas as localidades para cada período e estimamos a proporção de anuros de cada espécie ativa em cada período com base no número total de indivíduos e no número de espécies encontradas durante todas as buscas naquele período. Nós registramos um total de 817 indivíduos pertencentes a 69 espécies. A riqueza de espécies foi maior à noite (mediana = 12 espécies), intermediária ao crepúsculo (mediana = 8) e menor durante o dia (mediana = 4). A porcentagem do número total de indivíduos encontrados (todas as espécies agrupadas) foi maior durante a noite (ca. 53%) e menor durante o período diurno (ca. 14%). Analisando cada espécie separadamente, o número de indivíduos registrados foi consistentemente maior ao crepúsculo e à noite para a maioria das espécies. Nosso estudo evidencia uma tendência para atividade noturna para a maioria dos anuros da Mata Atlântica, com poucas espécies tendo hábitos primariamente diurnos. Esses resultados podem favorecer futuros estudos e esforços de conservação para as espécies de anfíbios.(AU)

Anurofauna of an Atlantic Rainforest fragment and its surroundings in Northern Rio de Janeiro State, Brazil.

We carried out a study on the anurofaunal community from an Atlantic Forest fragment (Monte Verde mountains) and the surrounding area in Cambuci municipality, Rio de Janeiro State, Brazil, which constitutes one of the largest fragments remaining in the largely deforested landscape of the northern portion of the State. We combined three sampling methods: plot sampling, transects and pit-fall traps. We recorded twenty species of amphibians, of which only eleven were found within the forest fragment (and five of these also occurred in the surrounding matrix). Two of the species recorded in the present study (Crossodactylus sp. and Ischnocnema cf. parva) may represent undescribed taxa. Our records expand the distribution range of one species (Scinax trapicheiroi) to the north, and fill a geographic distribution gap for another one (Ischnocnema oea). The estimated overall density of frogs living in the leaf litter of the fragment (based on results of plot sampling) was 3.1 individuals/100 m², with Haddadus binotatus being the most abundant species (2.4 individuals/100 m²). Comparisons of our data with those of other studies suggest that anuran communities in forest fragments ca. 1,000 ha or smaller may be severely limited in their richness, and often include a large proportion of species tolerant to open areas, such as many hylids. Our results show the importance of increasing knowledge about the anurofaunal community of the northern portion of the State of Rio de Janeiro and preserve the forest remnants that still exist in the region.