Selection and use of calling site by Boana leptolineata and Phyllomedusa distincta during the reproductive season / Seleção e uso de sítios de vocalização por Boana leptolineata e Phyllomedusa distincta durante o período reprodutivo

Climatic conditions and microhabitat characteristics, such as the substrate and type of vegetation, influence the choice of male anurans for calling sites that optimize their reproductive success. We evaluated the structure and selection of vocalization microhabitat of 17 individuals of Phyllomedusa distincta Lutz, 1950 and 25 of Boana leptolineata (Braun & Braun, 1977), in a subtropical forest in southern Brazil. We measure the height of the perch, the distance between the perch and the edge of the body of water and the structure of the microhabitat of quadrants used by individuals. The same attributes were measured in the quadrants available (but not used) by the individuals. We classified the microhabitats by visual estimate, assigning percentages of coverage for each quadrant by herbaceous, shrub, tree and wetland vegetation. We observed that both species selected their microhabitat, since the characteristics of the quadrants occupied by the individuals were different from those available. Phyllomedusa distincta was more associated with heterogeneous microhabitats, while B. leptolineata occurred in environments with greater coverage of tree strata. Additionally, we observed that both species used shrubs more frequently as a perch site. The selection of these microhabitat characteristics must be associated with strategies to optimize the use of the reproductive habitat, based on the morphological and behavioral characteristics of the species. Finally, it is possible to infer that the differences observed in the microhabitat structure selected by the species can facilitate the coexistence of both in the context of the heterogeneity of the environment.(AU)

Seleção e uso de sítios de vocalização por Boana leptolineata e Phyllomedusa distincta durante o período reprodutivoAs condições climáticas e as características de micro-habitat, como o substrato e o tipo de vegetação, influenciam a escolha de anuros machos por sítios de vocalização que otimizem seu sucesso reprodutivo. Avaliamos a estrutura e a seleção de micro-habitat de vocalização de 17 indivíduos de Phyllomedusa distincta Lutz, 1950 e 25 de Boana leptolineata (Braun & Braun, 1977), em uma floresta subtropical no sul do Brasil. Medimos a altura do poleiro, a distância do poleiro até a margem do corpo dágua e a estrutura do micro-habitat de quadrantes utilizados pelos indivíduos. Os mesmos atributos foram mensurados nos quadrantes disponíveis (mas não utilizados) pelos indivíduos. Classificamos os micro-habitats por estimativa visual, atribuindo-se porcentagens de cobertura de cada quadrante por vegetação herbácea, arbustiva, arbórea e de área alagada. Observamos que ambas as espécies selecionaram seu micro-habitat, uma vez que as características dos quadrantes ocupados pelos indivíduos foram distintas daquelas disponíveis. Phyllomedusa distincta esteve mais associada a micro-habitats heterogêneos, enquanto B. leptolineata ocorreu em ambientes com maior cobertura de estrato arbóreo. Adicionalmente, observamos que ambas as espécies utilizaram mais frequentemente arbustos como local do poleiro. A seleção destas características de micro-habitat deve estar associada a estratégias para otimização do uso do habitat reprodutivo, baseadas em características morfológicas e comportamentais das espécies. Por fim, é possível inferir que as diferenças observadas na estrutura de micro-habitat selecionadas pelas espécies podem facilitar a coexistência de ambas no contexto da heterogeneidade do ambiente.(AU)

Selection and use of calling site by Boana leptolineata and Phyllomedusa distincta during the reproductive season / Seleção e uso de sítios de vocalização por Boana leptolineata e Phyllomedusa distincta durante o período reprodutivo

Climatic conditions and microhabitat characteristics, such as the substrate and type of vegetation, influence the choice of male anurans for calling sites that optimize their reproductive success. We evaluated the structure and selection of vocalization microhabitat of 17 individuals of Phyllomedusa distincta Lutz, 1950 and 25 of Boana leptolineata (Braun & Braun, 1977), in a subtropical forest in southern Brazil. We measure the height of the perch, the distance between the perch and the edge of the body of water and the structure of the microhabitat of quadrants used by individuals. The same attributes were measured in the quadrants available (but not used) by the individuals. We classified the microhabitats by visual estimate, assigning percentages of coverage for each quadrant by herbaceous, shrub, tree and wetland vegetation. We observed that both species selected their microhabitat, since the characteristics of the quadrants occupied by the individuals were different from those available. Phyllomedusa distincta was more associated with heterogeneous microhabitats, while B. leptolineata occurred in environments with greater coverage of tree strata. Additionally, we observed that both species used shrubs more frequently as a perch site. The selection of these microhabitat characteristics must be associated with strategies to optimize the use of the reproductive habitat, based on the morphological and behavioral characteristics of the species. Finally, it is possible to infer that the differences observed in the microhabitat structure selected by the species can facilitate the coexistence of both in the context of the heterogeneity of the environment.

Seleção e uso de sítios de vocalização por Boana leptolineata e Phyllomedusa distincta durante o período reprodutivoAs condições climáticas e as características de micro-habitat, como o substrato e o tipo de vegetação, influenciam a escolha de anuros machos por sítios de vocalização que otimizem seu sucesso reprodutivo. Avaliamos a estrutura e a seleção de micro-habitat de vocalização de 17 indivíduos de Phyllomedusa distincta Lutz, 1950 e 25 de Boana leptolineata (Braun & Braun, 1977), em uma floresta subtropical no sul do Brasil. Medimos a altura do poleiro, a distância do poleiro até a margem do corpo d’água e a estrutura do micro-habitat de quadrantes utilizados pelos indivíduos. Os mesmos atributos foram mensurados nos quadrantes disponíveis (mas não utilizados) pelos indivíduos. Classificamos os micro-habitats por estimativa visual, atribuindo-se porcentagens de cobertura de cada quadrante por vegetação herbácea, arbustiva, arbórea e de área alagada. Observamos que ambas as espécies selecionaram seu micro-habitat, uma vez que as características dos quadrantes ocupados pelos indivíduos foram distintas daquelas disponíveis. Phyllomedusa distincta esteve mais associada a micro-habitats heterogêneos, enquanto B. leptolineata ocorreu em ambientes com maior cobertura de estrato arbóreo. Adicionalmente, observamos que ambas as espécies utilizaram mais frequentemente arbustos como local do poleiro. A seleção destas características de micro-habitat deve estar associada a estratégias para otimização do uso do habitat reprodutivo, baseadas em características morfológicas e comportamentais das espécies. Por fim, é possível inferir que as diferenças observadas na estrutura de micro-habitat selecionadas pelas espécies podem facilitar a coexistência de ambas no contexto da heterogeneidade do ambiente.

Selection and use of calling site by Boana leptolineata and Phyllomedusa distincta during the reproductive season

ABSTRACT Climatic conditions and microhabitat characteristics, such as the substrate and type of vegetation, influence the choice of male anurans for calling sites that optimize their reproductive success. We evaluated the structure and selection of vocalization microhabitat of 17 individuals of Phyllomedusa distincta Lutz, 1950 and 25 of Boana leptolineata (Braun & Braun, 1977), in a subtropical forest in southern Brazil. We measure the height of the perch, the distance between the perch and the edge of the body of water and the structure of the microhabitat of quadrants used by individuals. The same attributes were measured in the quadrants available (but not used) by the individuals. We classified the microhabitats by visual estimate, assigning percentages of coverage for each quadrant by herbaceous, shrub, tree and wetland vegetation. We observed that both species selected their microhabitat, since the characteristics of the quadrants occupied by the individuals were different from those available. Phyllomedusa distincta was more associated with heterogeneous microhabitats, while B. leptolineata occurred in environments with greater coverage of tree strata. Additionally, we observed that both species used shrubs more frequently as a perch site. The selection of these microhabitat characteristics must be associated with strategies to optimize the use of the reproductive habitat, based on the morphological and behavioral characteristics of the species. Finally, it is possible to infer that the differences observed in the microhabitat structure selected by the species can facilitate the coexistence of both in the context of the heterogeneity of the environment.

RESUMO Seleção e uso de sítios de vocalização por Boana leptolineata e Phyllomedusa distincta durante o período reprodutivoAs condições climáticas e as características de micro-habitat, como o substrato e o tipo de vegetação, influenciam a escolha de anuros machos por sítios de vocalização que otimizem seu sucesso reprodutivo. Avaliamos a estrutura e a seleção de micro-habitat de vocalização de 17 indivíduos de Phyllomedusa distincta Lutz, 1950 e 25 de Boana leptolineata (Braun & Braun, 1977), em uma floresta subtropical no sul do Brasil. Medimos a altura do poleiro, a distância do poleiro até a margem do corpo dágua e a estrutura do micro-habitat de quadrantes utilizados pelos indivíduos. Os mesmos atributos foram mensurados nos quadrantes disponíveis (mas não utilizados) pelos indivíduos. Classificamos os micro-habitats por estimativa visual, atribuindo-se porcentagens de cobertura de cada quadrante por vegetação herbácea, arbustiva, arbórea e de área alagada. Observamos que ambas as espécies selecionaram seu micro-habitat, uma vez que as características dos quadrantes ocupados pelos indivíduos foram distintas daquelas disponíveis. Phyllomedusa distincta esteve mais associada a micro-habitats heterogêneos, enquanto B. leptolineata ocorreu em ambientes com maior cobertura de estrato arbóreo. Adicionalmente, observamos que ambas as espécies utilizaram mais frequentemente arbustos como local do poleiro. A seleção destas características de micro-habitat deve estar associada a estratégias para otimização do uso do habitat reprodutivo, baseadas em características morfológicas e comportamentais das espécies. Por fim, é possível inferir que as diferenças observadas na estrutura de micro-habitat selecionadas pelas espécies podem facilitar a coexistência de ambas no contexto da heterogeneidade do ambiente.

Microhabitat selection of the poorly known lizard Tropidurus lagunablanca (Squamata: Tropiduridae) in the Pantanal, Brazil

Abstract Understanding how different environmental factors influence species occurrence is a key issue to address the study of natural populations. However, there is a lack of knowledge on how local traits influence the microhabitat use of tropical arboreal lizards. Here, we investigated the microhabitat selection of the poorly known lizard Tropidurus lagunablanca (Squamata: Tropiduridae) and evaluated how environmental microhabitat features influence animals presence. We used a Resource Selection Function approach, in a case/control design where we analyzed the effect of substrate temperature and trees diameter at breast height (DBH) in the probability of presence of lizards using mixed Conditional Logistic Regression. We found that T. lagunablanca uses trees with DBH from 0.40 m to 4 m and substrate temperatures ranging from 25.9°C to 42°C. Moreover, we showed that thickness of the trees and substrate temperatures significantly increased the probability of presence of T. lagunablanca individuals, being the probability of presence higher than 50% for trees up to 1.5 m DBH and temperature of substrate up to 37.5°C. Our study probed that T. lagunablanca individuals choose trees non-randomly, selecting thicker and warmer tree trunks. This information advances the knowledge of the spatial ecology of Neotropical arboreal lizards and is relevant for conservation, putting an emphasis on preserving native vegetation in the Pantanal.

Microhabitat selection of the poorly known lizard Tropidurus lagunablanca (Squamata: Tropiduridae) in the Pantanal, Brazil

Abstract Understanding how different environmental factors influence species occurrence is a key issue to address the study of natural populations. However, there is a lack of knowledge on how local traits influence the microhabitat use of tropical arboreal lizards. Here, we investigated the microhabitat selection of the poorly known lizard Tropidurus lagunablanca (Squamata: Tropiduridae) and evaluated how environmental microhabitat features influence animal's presence. We used a Resource Selection Function approach, in a case/control design where we analyzed the effect of substrate temperature and tree's diameter at breast height (DBH) in the probability of presence of lizards using mixed Conditional Logistic Regression. We found that T. lagunablanca uses trees with DBH from 0.40 m to 4 m and substrate temperatures ranging from 25.9°C to 42°C. Moreover, we showed that thickness of the trees and substrate temperatures significantly increased the probability of presence of T. lagunablanca individuals, being the probability of presence higher than 50% for trees up to 1.5 m DBH and temperature of substrate up to 37.5°C. Our study probed that T. lagunablanca individuals choose trees non-randomly, selecting thicker and warmer tree trunks. This information advances the knowledge of the spatial ecology of Neotropical arboreal lizards and is relevant for conservation, putting an emphasis on preserving native vegetation in the Pantanal.

Microhabitat selection of the poorly known lizard Tropidurus lagunablanca(Squamata: Tropiduridae) in the Pantanal, Brazil

Understanding how different environmental factors influence species occurrence is a key issue to address the study of natural populations. However, there is a lack of knowledge on how local traits influence the microhabitat use of tropical arboreal lizards. Here, we investigated the microhabitat selection of the poorly known lizard Tropidurus lagunablanca(Squamata: Tropiduridae) and evaluated how environmental microhabitat features influence animals presence. We used a Resource Selection Function approach, in a case/control design where we analyzed the effect of substrate temperature and trees diameter at breast height (DBH) in the probability of presence of lizards using mixed Conditional Logistic Regression. We found that T. lagunablanca uses trees with DBH from 0.40 m to 4 m and substrate temperatures ranging from 25.9°C to 42°C. Moreover, we showed that thickness of the trees and substrate temperatures significantly increased the probability of presence of T. lagunablanca individuals, being the probability of presence higher than 50% for trees up to 1.5 m DBH and temperature of substrate up to 37.5°C. Our study probed that T. lagunablanca individuals choose trees non-randomly, selecting thicker and warmer tree trunks. This information advances the knowledge of the spatial ecology of Neotropical arboreal lizards and is relevant for conservation, putting an emphasis on preserving native vegetation in the Pantanal.(AU)

Habitat structure and their influence in lizard's presence

Many species are declining due to environmental and physical changes in their habitats. Such disturbs alter the availability of micro-habitats and influences the presence of lizards, being even worse for threatened and endemic species. Glaucomastix littoralis is a teiid species restricted to four restingas areas of Brazil. The understanding about the use and preferences of micro-habitats by the species and the consequents effects of substrate loss is important to prevent local extinctions. This study took place in restingas of Maricá, Jurubatiba and Grussaí, in Rio de Janeiro State. We sampled the vegetation of all areas, to access differences between the physical structures, and recorded the individuals sighted and the micro-habitat they were in, to investigate the relation of individuals and habitat structure. We calculated the frequency utilization of each micro-habitat and made a presence estimation of individuals (occupancy and detection probability) to assess which structural parameters of vegetation guide the settlement of the studied populations. Our data showed structural vegetation particularities among the areas and a trend concerning the use of micro-habitat by Glaucomastix littoralis, with a general preference for leaf litter inside bushes, guriri and bare sand and a low utilization of cactus and herbaceous. We also found positives (bare sand and cactus) and negatives (bushes) influences of micro-habitats in relation to the occupation of the areas by the individuals. Since vegetation is fundamental to lizards, due to their use as a refuge, site for thermoregulation and feeding, the understanding about the effects habitat degradation/fragmentation can cause is essential to create appropriate management plans and develop public policies to conserve the species.

Habitat structure and their influence in lizard's presence

Many species are declining due to environmental and physical changes in their habitats. Such disturbs alter the availability of micro-habitats and influences the presence of lizards, being even worse for threatened and endemic species. Glaucomastix littoralis is a teiid species restricted to four restingas areas of Brazil. The understanding about the use and preferences of micro-habitats by the species and the consequents effects of substrate loss is important to prevent local extinctions. This study took place in restingas of Maricá, Jurubatiba and Grussaí, in Rio de Janeiro State. We sampled the vegetation of all areas, to access differences between the physical structures, and recorded the individuals sighted and the micro-habitat they were in, to investigate the relation of individuals and habitat structure. We calculated the frequency utilization of each micro-habitat and made a presence estimation of individuals (occupancy and detection probability) to assess which structural parameters of vegetation guide the settlement of the studied populations. Our data showed structural vegetation particularities among the areas and a trend concerning the use of micro-habitat by Glaucomastix littoralis, with a general preference for leaf litter inside bushes, guriri and bare sand and a low utilization of cactus and herbaceous. We also found positives (bare sand and cactus) and negatives (bushes) influences of micro-habitats in relation to the occupation of the areas by the individuals. Since vegetation is fundamental to lizards, due to their use as a refuge, site for thermoregulation and feeding, the understanding about the effects habitat degradation/fragmentation can cause is essential to create appropriate management plans and develop public policies to conserve the species.(AU)

Thermal biology of Amphisbaena munoai (Squamata: Amphisbaenidae)

Studies on the thermal biology of fossorial reptiles that examine the relationship between the body temperature and thermal environment are needed to determine the extent of their thermoregulation abilities. This study assessed the thermal biology of Amphisbaena munoai Klappenbach, 1969 in the rocky fields of the Rio Grande do Sul and in the laboratory. The body temperature of most individuals was between 24 and 30 °C, both in the field (n = 81) and laboratory (n = 19). More individuals were caught in winter (n = 55) and spring (n = 60) than in summer (n = 25) and fall (n = 45), and in spring, individuals showed similar nocturnal and diurnal activities. In the laboratory, we found individuals with body temperatures up to 5 °C higher than the ambient temperature (n = 4), suggesting that some physiological mechanisms participate in the thermoregulation of these animals. Amphisbaena munoai is a thigmothermic species that is capable of actively regulating its temperature by selecting microhabitats such that its various activities occur within an ideal temperature range. This study is the first to evaluate the effect of seasonality and diurnal and nocturnal variations on the thermoregulation of an amphisbaenid.

Thermal biology of Amphisbaena munoai (Squamata: Amphisbaenidae)

Studies on the thermal biology of fossorial reptiles that examine the relationship between the body temperature and thermal environment are needed to determine the extent of their thermoregulation abilities. This study assessed the thermal biology of Amphisbaena munoai Klappenbach, 1969 in the rocky fields of the Rio Grande do Sul and in the laboratory. The body temperature of most individuals was between 24 and 30 °C, both in the field (n = 81) and laboratory (n = 19). More individuals were caught in winter (n = 55) and spring (n = 60) than in summer (n = 25) and fall (n = 45), and in spring, individuals showed similar nocturnal and diurnal activities. In the laboratory, we found individuals with body temperatures up to 5 °C higher than the ambient temperature (n = 4), suggesting that some physiological mechanisms participate in the thermoregulation of these animals. Amphisbaena munoai is a thigmothermic species that is capable of actively regulating its temperature by selecting microhabitats such that its various activities occur within an ideal temperature range. This study is the first to evaluate the effect of seasonality and diurnal and nocturnal variations on the thermoregulation of an amphisbaenid.(AU)

Body orientation for thermoregulation and daily activity cycle of Mabuya macrorhyncha (Squamata: Scincidae)

We investigated the daily activity and thermoregulatory body orientation of Mabuya macrorhyncha (Hoge, 1947), a lizard species that occurs in the Brazilian Atlantic Forest. We conducted this investigation in a sandy coastal dune remnant (restinga ecosystem) in Grussaí, state of Rio de Janeiro, Brazil, during the summer. The daily activity cycle of the lizards started around 6:00 am and ended before 7:00 pm. This is longer than observed in other populations of M. macrorhyncha (approximately 7:00 am to 5:00 pm). The activity cycle of the lizards was bimodal, with the first peak between 6:00 and 11:00 am and the second from 2:00 to 7:00 pm. This contrasts with observations on other populations of this species, which revealed an unimodal pattern. The mean body temperature of M. macrorhyncha in Grussaí was 34.2 ± 1.5 °C, which was comparatively higher than observed in other populations of the species. The differences in the daily activity and of body temperature of these lizards between our study and previous studies on this species may reflect environmental thermal conditions. The mean air and mean substrate temperatures when individuals were active were 27.8 and 30.5 °C respectively. Lizard orientation was significantly correlated with the direction of the solar incidence, suggesting that solar radiation, and particularly behavioral adjustments that maximize exposure to the sun, are important for the thermoregulation of M. macrorhyncha. Circular structures at the site, such as bromeliads, offer microhabitats with different orientations to the sunlight, favoring lizard thermoregulatory behaviors.

Body orientation for thermoregulation and daily activity cycle of Mabuya macrorhyncha (Squamata: Scincidae)

We investigated the daily activity and thermoregulatory body orientation of Mabuya macrorhyncha (Hoge, 1947), a lizard species that occurs in the Brazilian Atlantic Forest. We conducted this investigation in a sandy coastal dune remnant (restinga ecosystem) in Grussaí, state of Rio de Janeiro, Brazil, during the summer. The daily activity cycle of the lizards started around 6:00 am and ended before 7:00 pm. This is longer than observed in other populations of M. macrorhyncha (approximately 7:00 am to 5:00 pm). The activity cycle of the lizards was bimodal, with the first peak between 6:00 and 11:00 am and the second from 2:00 to 7:00 pm. This contrasts with observations on other populations of this species, which revealed an unimodal pattern. The mean body temperature of M. macrorhyncha in Grussaí was 34.2 ± 1.5 °C, which was comparatively higher than observed in other populations of the species. The differences in the daily activity and of body temperature of these lizards between our study and previous studies on this species may reflect environmental thermal conditions. The mean air and mean substrate temperatures when individuals were active were 27.8 and 30.5 °C respectively. Lizard orientation was significantly correlated with the direction of the solar incidence, suggesting that solar radiation, and particularly behavioral adjustments that maximize exposure to the sun, are important for the thermoregulation of M. macrorhyncha. Circular structures at the site, such as bromeliads, offer microhabitats with different orientations to the sunlight, favoring lizard thermoregulatory behaviors.(AU)

Padrões de uso de tocas por mamíferos em área de floresta estacional semidecidual no sul do Brasil / Patterns in use of burrows by mammals in a semi-deciduous season forest area in south Brazil

O objetivo do estudo foi identificar e caracterizar tocas de tatu encontradas em remanescente de floresta semidecidual empregando os métodos de caminhamento, análise de micro-habitat e armadilhas fotográficas. A maioria das tocas foi escavada sob rochas ou raízes de árvores e estão associadas a diferentes níveis de cobertura vegetal. Foram registradas ao menos quatro espécies de mamíferos, indicando que tatus podem ser engenheiros de ecossistemas.

The aim of this study was to identify and characterize armadillo burrows found in a semideciduous forest remnant employing methods of random-walks, micro-habitat analysis and camera-traps. Most burrows (60,6%) were excavated under rocks or tree roots and are associated to different levels of vegetation cover. Three medium and large sized mammals were registered besides small wild rodents, indicating that armadillos may be ecosystem engineers.

Padrões de uso de tocas por mamíferos em área de floresta estacional semidecidual no sul do Brasil / Patterns in use of burrows by mammals in a semi-deciduous season forest area in south Brazil

O objetivo do estudo foi identificar e caracterizar tocas de tatu encontradas em remanescente de floresta semidecidual empregando os métodos de caminhamento, análise de micro-habitat e armadilhas fotográficas. A maioria das tocas foi escavada sob rochas ou raízes de árvores e estão associadas a diferentes níveis de cobertura vegetal. Foram registradas ao menos quatro espécies de mamíferos, indicando que tatus podem ser engenheiros de ecossistemas.(AU)

The aim of this study was to identify and characterize armadillo burrows found in a semideciduous forest remnant employing methods of random-walks, micro-habitat analysis and camera-traps. Most burrows (60,6%) were excavated under rocks or tree roots and are associated to different levels of vegetation cover. Three medium and large sized mammals were registered besides small wild rodents, indicating that armadillos may be ecosystem engineers.(AU)

Resource use by two electric fishes (Gymnotiformes) of the National Forest Saracá-Taquera, Oriximiná, Pará

Fishes of the order Gymnotiformes have high diversity of oral and head morphology, which suggests trophic specializations within each clade. The aim of this study was to describe resource use patterns by two fish species (Gymnorhamphichthys rondoni and Gymnotus coropinae) in the National Forest Saracá-Taquera, Oriximiná - Pará, analyzing microhabitat use, diet composition, feeding strategies, niche breadth and niche overlap. Stomach contents of 101 individuals (41 G. rondoni and 60 G. coropinae), sampled in 23 headwater streams were analyzed and volume of food items was quantified to characterize their feeding ecology. Gymnorhamphichthys rondoni was captured mainly on sandy bottoms, whereas G. coropinae in crevices. Both species had a zoobenthivorous diet and consumed predominantly Sediment/Detritus and Diptera larvae, but also included allochthonous prey in their diet. These species had high niche overlap, with small variations related to the higher consumption of Ceratopogonidae larvae by G. rondoni and of Chironomidae larvae by G. coropinae. Both species had a generalist feeding strategy, but G. coropinae had a broader niche breadth. Our results demonstrate that G. rondoni and G. coropinae occupy different microhabitats but rely on similar food resources.(AU)

Peixes da ordem Gymnotiformes apresentam alta diversidade morfológica, o que sugere a existência de especializações tróficas dentro dos clados. O objetivo deste estudo foi analisar o uso de recursos por duas espécies de peixes elétricos (Gymnorhamphichthys rondoni e Gymnotus coropinae) na Floresta Nacional Saracá-Taquera, Oriximiná - Pará, analisando o uso de microhabitats, composição da dieta, estratégias alimentares, amplitude de nicho e sobreposição de nicho. Conteúdos estomacais de 101 indivíduos (41 G. rondoni e 60 G. coropinae), capturados em 23 igarapés de cabeceira, foram analisados e quantificados volumetricamente para a caracterização da ecologia trófica. Gymnorhamphichthys rondoni foi registrada principalmente em bancos de areia, enquanto G. coropinae em fendas. Ambas as espécies apresentaram dieta zoobentívora e consumiram predominantemente sedimento/detritos e larvas de Diptera, mas também consumiram presas alóctones. Foi observada alta sobreposição de nicho trófico e a baixa variação encontrada foi relacionada à maior utilização de larvas de Chironomidae por G. rondoni e de larvas de Ceratopogonidae por G. coropinae. Ambas as espécies apresentaram estratégia alimentar generalista, porém G. coropinae apresentou maior amplitude de nicho. Nossos resultados demonstram que G. rondoni e G. coropinae ocupam microhabitats diferentes, mas dependem de recursos alimentares similares.(AU)

Resource use by two electric fishes (Gymnotiformes) of the National Forest Saracá-Taquera, Oriximiná, Pará

Fishes of the order Gymnotiformes have high diversity of oral and head morphology, which suggests trophic specializations within each clade. The aim of this study was to describe resource use patterns by two fish species (Gymnorhamphichthys rondoni and Gymnotus coropinae) in the National Forest Saracá-Taquera, Oriximiná - Pará, analyzing microhabitat use, diet composition, feeding strategies, niche breadth and niche overlap. Stomach contents of 101 individuals (41 G. rondoni and 60 G. coropinae), sampled in 23 headwater streams were analyzed and volume of food items was quantified to characterize their feeding ecology. Gymnorhamphichthys rondoni was captured mainly on sandy bottoms, whereas G. coropinae in crevices. Both species had a zoobenthivorous diet and consumed predominantly Sediment/Detritus and Diptera larvae, but also included allochthonous prey in their diet. These species had high niche overlap, with small variations related to the higher consumption of Ceratopogonidae larvae by G. rondoni and of Chironomidae larvae by G. coropinae. Both species had a generalist feeding strategy, but G. coropinae had a broader niche breadth. Our results demonstrate that G. rondoni and G. coropinae occupy different microhabitats but rely on similar food resources.(AU)

Peixes da ordem Gymnotiformes apresentam alta diversidade morfológica, o que sugere a existência de especializações tróficas dentro dos clados. O objetivo deste estudo foi analisar o uso de recursos por duas espécies de peixes elétricos (Gymnorhamphichthys rondoni e Gymnotus coropinae) na Floresta Nacional Saracá-Taquera, Oriximiná - Pará, analisando o uso de microhabitats, composição da dieta, estratégias alimentares, amplitude de nicho e sobreposição de nicho. Conteúdos estomacais de 101 indivíduos (41 G. rondoni e 60 G. coropinae), capturados em 23 igarapés de cabeceira, foram analisados e quantificados volumetricamente para a caracterização da ecologia trófica. Gymnorhamphichthys rondoni foi registrada principalmente em bancos de areia, enquanto G. coropinae em fendas. Ambas as espécies apresentaram dieta zoobentívora e consumiram predominantemente sedimento/detritos e larvas de Diptera, mas também consumiram presas alóctones. Foi observada alta sobreposição de nicho trófico e a baixa variação encontrada foi relacionada à maior utilização de larvas de Chironomidae por G. rondoni e de larvas de Ceratopogonidae por G. coropinae. Ambas as espécies apresentaram estratégia alimentar generalista, porém G. coropinae apresentou maior amplitude de nicho. Nossos resultados demonstram que G. rondoni e G. coropinae ocupam microhabitats diferentes, mas dependem de recursos alimentares similares.(AU)

Diet of Dendropsophus microcephalus and Scarthyla vigilans (Anura: Hylidae) at a locality in north-western Venezuela with notes on microhabitat occupation

The coexistence of species with similar ecological requirements (food, space, time) has typically drawn attention of researchers because competition for resources is expected to be high. The diet and microhabitat occupation of two morphologically and ecologically similar species of Hylidae (Anura), Dendropsophus microcephalus and Scarthyla vigilans, were analyzed at a locality in north-western Venezuela, with the aim of addressing the potential for space and food competition between them. Diet was estimated through the analysis of stomach contents and microhabitat occupation was estimated through recordings of perch type, height and horizontal distance to water. Thirty-six prey categories (32 families, 4 orders) of arthropods were identified: 30 categories in D. microcephalus and 21 categories in S. vigilans. The most important prey (RII) in D. microcephalus were Agelenidae (11.1%), Tachinidae (9.32%) and Lepidoptera-larvae (7.96%). Gryllidae (14.13%), Cicadidae (9.1%), Cicadellidae (8.3%) and Delphacidae (8.02%) were the most important in S. vigilans. Diet overlap was relatively low (0.32). Both species have relatively generalist diets. Both species occupied the same type of perches (leaves and stems of Dicotyledons and Monocotyledons) and heights (average: S. vigilans, 24 ± 16.2 cm; D. microcephalus, 22.7 ± 9.5 cm). The potential for space competition is high if perches are limited and food competition is expected to be low.

La coexistencia de especies con requerimientos ecológicos similares (alimento, espacio, tiempo) típicamente ha atraído a los investigadores porque se espera que la competencia por recursos sea alta. La dieta y la ocupación de microhábitat de dos especies morfológica y ecológicamente similares de Hylidae (Anura) se analizaron en una localidad al noroeste de Venezuela, con el objetivo de evaluar el potencial para competencia entre ellas. La dieta se estimó a través del análisis de los contenidos estomacales y la ocupación del microhábitat por medio de registros del tipo y altura de la percha y la distancia horizontal al agua. Se identificaron 36 categorías de presa (32 familias, 4 órdenes); 30 en D. microcephalus y 21 en S. vigilans. Las presas más importantes (RII) en D. microcephalus fueron Agelenidae (11,1%), Tachinidae (9,32%) y Lepidoptera-larva (7,96%). Gryllidae (14,13%), Cicadidae (9,1%), Cicadellidae (8,3%) and Delphacidae (8,02%) fueron las más importantes en S. vigilans. Ambas especies tienen dietas relativamente generalistas. La superposición de las dietas fue relativamente baja (0,32). Ambas especies ocuparon el mismo tipo de perchas (hojas y tallos de dicotiledóneas y monocotiledóneas) a las mismas alturas. El potencial para la competencia por espacio es alto si las perchas fuesen escasas, pero se espera que la competencia por el alimento sea baja.

Diet of dendropsophus microcephalus and scarthyla vigilans (anura: hylidae) at a locality in north-western venezuela with notes on microhabitat occupation

RESUMEN La coexistencia de especies con requerimientos ecológicos similares (alimento, espacio, tiempo) típicamente ha atraído a los investigadores porque se espera que la competencia por recursos sea alta. La dieta y la ocupación de microhábitat de dos especies morfológica y ecológicamente similares de Hylidae (Anura) se analizaron en una localidad al noroeste de Venezuela, con el objetivo de evaluar el potencial para competencia entre ellas. La dieta se estimó a través del análisis de los contenidos estomacales y la ocupación del microhábitat por medio de registros del tipo y altura de la percha y la distancia horizontal al agua. Se identificaron 36 categorías de presa (32 familias, 4 órdenes); 30 en D. microcephalus y 21 en S. vigilans. Las presas más importantes (RII) en D. microcephalus fueron Agelenidae (11,1%), Tachinidae (9,32%) y Lepidoptera-larva (7,96%). Gryllidae (14,13%), Cicadidae (9,1%), Cicadellidae (8,3%) and Delphacidae (8,02%) fueron las más importantes en S. vigilans. Ambas especies tienen dietas relativamente generalistas. La superposición de las dietas fue relativamente baja (0,32). Ambas especies ocuparon el mismo tipo de perchas (hojas y tallos de dicotiledóneas y monocotiledóneas) a las mismas alturas. El potencial para la competencia por espacio es alto si las perchas fuesen escasas, pero se espera que la competencia por el alimento sea baja.

ABSTRACT The coexistence of species with similar ecological requirements (food, space, time) has typically drawn attention of researchers because competition for resources is expected to be high. The diet and microhabitat occupation of two morphologically and ecologically similar species of Hylidae (Anura), Dendropsophus microcephalus and Scarthyla vigilans, were analyzed at a locality in north-western Venezuela, with the aim of addressing the potential for space and food competition between them. Diet was estimated through the analysis of stomach contents and microhabitat occupation was estimated through recordings of perch type, height and horizontal distance to water. Thirty-six prey categories (32 families, 4 orders) of arthropods were identified: 30 categories in D. microcephalus and 21 categories in S. vigilans. The most important prey (RII) in D. microcephalus were Agelenidae (11.1%), Tachinidae (9.32%) and Lepidoptera-larvae (7.96%). Gryllidae (14.13%), Cicadidae (9.1%), Cicadellidae (8.3%) and Delphacidae (8.02%) were the most important in S. vigilans. Diet overlap was relatively low (0.32). Both species have relatively generalist diets. Both species occupied the same type of perches (leaves and stems of Dicotyledons and Monocotyledons) and heights (average: S. vigilans, 24 ± 16.2 cm; D. microcephalus, 22.7 ± 9.5 cm). The potential for space competition is high if perches are limited and food competition is expected to be low.

DIET OF DENDROPSOPHUS MICROCEPHALUS AND SCARTHYLA VIGILANS (ANURA: HYLIDAE) AT A LOCALITY IN NORTH-WESTERN VENEZUELA WITH NOTES ON MICROHABITAT OCCUPATION

RESUMEN La coexistencia de especies con requerimientos ecológicos similares (alimento, espacio, tiempo) típicamente ha atraído a los investigadores porque se espera que la competencia por recursos sea alta. La dieta y la ocupación de microhábitat de dos especies morfológica y ecológicamente similares de Hylidae (Anura) se analizaron en una localidad al noroeste de Venezuela, con el objetivo de evaluar el potencial para competencia entre ellas. La dieta se estimó a través del análisis de los contenidos estomacales y la ocupación del microhábitat por medio de registros del tipo y altura de la percha y la distancia horizontal al agua. Se identificaron 36 categorías de presa (32 familias, 4 órdenes); 30 en D. microcephalus y 21 en S. vigilans. Las presas más importantes (RII) en D. microcephalus fueron Agelenidae (11,1%), Tachinidae (9,32%) y Lepidoptera-larva (7,96%). Gryllidae (14,13%), Cicadidae (9,1%), Cicadellidae (8,3%) and Delphacidae (8,02%) fueron las más importantes en S. vigilans. Ambas especies tienen dietas relativamente generalistas. La superposición de las dietas fue relativamente baja (0,32). Ambas especies ocuparon el mismo tipo de perchas (hojas y tallos de dicotiledóneas y monocotiledóneas) a las mismas alturas. El potencial para la competencia por espacio es alto si las perchas fuesen escasas, pero se espera que la competencia por el alimento sea baja.

ABSTRACT The coexistence of species with similar ecological requirements (food, space, time) has typically drawn attention of researchers because competition for resources is expected to be high. The diet and microhabitat occupation of two morphologically and ecologically similar species of Hylidae (Anura), Dendropsophus microcephalus and Scarthyla vigilans, were analyzed at a locality in north-western Venezuela, with the aim of addressing the potential for space and food competition between them. Diet was estimated through the analysis of stomach contents and microhabitat occupation was estimated through recordings of perch type, height and horizontal distance to water. Thirty-six prey categories (32 families, 4 orders) of arthropods were identified: 30 categories in D. microcephalus and 21 categories in S. vigilans. The most important prey (RII) in D. microcephalus were Agelenidae (11.1%), Tachinidae (9.32%) and Lepidoptera-larvae (7.96%). Gryllidae (14.13%), Cicadidae (9.1%), Cicadellidae (8.3%) and Delphacidae (8.02%) were the most important in S. vigilans. Diet overlap was relatively low (0.32). Both species have relatively generalist diets. Both species occupied the same type of perches (leaves and stems of Dicotyledons and Monocotyledons) and heights (average: S. vigilans, 24 ± 16.2 cm; D. microcephalus, 22.7 ± 9.5 cm). The potential for space competition is high if perches are limited and food competition is expected to be low.

Diet of Dendropsophus microcephalus and Scarthyla vigilans (Anura: Hylidae) at a locality in north-western Venezuela with notes on microhabitat occupation

The coexistence of species with similar ecological requirements (food, space, time) has typically drawn attention of researchers because competition for resources is expected to be high. The diet and microhabitat occupation of two morphologically and ecologically similar species of Hylidae (Anura), Dendropsophus microcephalus and Scarthyla vigilans, were analyzed at a locality in north-western Venezuela, with the aim of addressing the potential for space and food competition between them. Diet was estimated through the analysis of stomach contents and microhabitat occupation was estimated through recordings of perch type, height and horizontal distance to water. Thirty-six prey categories (32 families, 4 orders) of arthropods were identified: 30 categories in D. microcephalus and 21 categories in S. vigilans. The most important prey (RII) in D. microcephalus were Agelenidae (11.1%), Tachinidae (9.32%) and Lepidoptera-larvae (7.96%). Gryllidae (14.13%), Cicadidae (9.1%), Cicadellidae (8.3%) and Delphacidae (8.02%) were the most important in S. vigilans. Diet overlap was relatively low (0.32). Both species have relatively generalist diets. Both species occupied the same type of perches (leaves and stems of Dicotyledons and Monocotyledons) and heights (average: S. vigilans, 24 ± 16.2 cm; D. microcephalus, 22.7 ± 9.5 cm). The potential for space competition is high if perches are limited and food competition is expected to be low.(AU)

La coexistencia de especies con requerimientos ecológicos similares (alimento, espacio, tiempo) típicamente ha atraído a los investigadores porque se espera que la competencia por recursos sea alta. La dieta y la ocupación de microhábitat de dos especies morfológica y ecológicamente similares de Hylidae (Anura) se analizaron en una localidad al noroeste de Venezuela, con el objetivo de evaluar el potencial para competencia entre ellas. La dieta se estimó a través del análisis de los contenidos estomacales y la ocupación del microhábitat por medio de registros del tipo y altura de la percha y la distancia horizontal al agua. Se identificaron 36 categorías de presa (32 familias, 4 órdenes); 30 en D. microcephalus y 21 en S. vigilans. Las presas más importantes (RII) en D. microcephalus fueron Agelenidae (11,1%), Tachinidae (9,32%) y Lepidoptera-larva (7,96%). Gryllidae (14,13%), Cicadidae (9,1%), Cicadellidae (8,3%) and Delphacidae (8,02%) fueron las más importantes en S. vigilans. Ambas especies tienen dietas relativamente generalistas. La superposición de las dietas fue relativamente baja (0,32). Ambas especies ocuparon el mismo tipo de perchas (hojas y tallos de dicotiledóneas y monocotiledóneas) a las mismas alturas. El potencial para la competencia por espacio es alto si las perchas fuesen escasas, pero se espera que la competencia por el alimento sea baja.(AU)