RESUMO

Predators directly and indirectly affect the density and the behavior of prey. These effects may potentially cascade down to lower trophic levels. In this study, we tested the effects of predator calls (playbacks of bird vocalizations: Tyto alba, Speotyto cunicularia, and Vanellus chilensis), predator visual stimuli (stuffed birds) and interactions of visual and auditory cues, on the behavior of frugivore phyllostomid bats in the field. In addition, we tested if the effects of predation risk cascade down to other trophic levels by measuring rates of seed dispersal of the tree Muntingia calabura. Using video recording, we found that bats significantly decreased the foraging frequency on trees when a visual cue of T. alba was present. However, no stimuli of potential predatory birds, including vocalization of T. alba, affected bat foraging frequency. There was a change in bat behavior during 7 min, but then their frequency of activity gradually increased. Consequently, the presence of T. alba decreased by up to ten times the rate of seed removal. These results indicate that risk sensitivity of frugivorous phyllostomid bats depends on predator identity and presence. Among the predators used in this study, only T. alba is an effective bat predator in the Neotropics. Sound stimuli of T. alba seem not to be a cue of predation risk, possibly because their vocalizations are used only for intraspecific communication. This study emphasizes the importance of evaluating different predator stimuli on the behavior of vertebrates, as well as the effects of these stimuli on trait-mediated trophic cascades.

Assuntos

RESUMO

The species composition and spatial distribution of a fish assemblage were studied in three reaches of a river in the east coast of Brazil: a section of rapids (upper), another of water flowing on plain terrain (lowland) and the other of a mangrove environment. Two methods were employed with the purpose of estimating their effectiveness in naturalistic studies of tropical fish assemblages. One method consisted of underwater observations and the other was characterized by catches using gears such as fish traps, sieves and fishing rods. Both methods showed that their effectiveness is dependent upon the characteristics of the environment and the biology of the species. In areas of high water transparency and flow speed rocky substrate and no submerged marginal vegetation (upper reach), the employment of the traditional gears was quite inefficient, despite the excellent conditions for underwater observations. In areas of clear water and high flow speed with abundant submerged marginal vegetation (lowland and mangrove), the gears were rather efficient yielding excellent results when coupled with direct observation methods. Since the abiotic characteristics of a stream change longitudinally, it is appropriate to employ different methods in the study of the ichthyofauna composition and distribution in order to reduce the constraints imposed by sampling methods in running waters.

Assuntos

RESUMO

The species composition and spatial distribution of a fish assemblage were studied in three reaches of a river in the east coast of Brazil: a section of rapids (upper), another of water flowing on plain terrain (lowland) and the other of a mangrove environment. Two methods were employed with the purpose of estimating their effectiveness in naturalistic studies of tropical fish assemblages. One method consisted of underwater observations and the other was characterized by catches using gears such as fish traps, sieves and fishing rods. Both methods showed that their effectiveness is dependent upon the characteristics of the environment and the biology of the species. In areas of high water transparency and flow speed, rocky substrate and no submerged marginal vegetation (upper reach), the employment of the traditional gears was quite inefficient, despite the excellent conditions for underwater observations. In areas of clear water and high flow speed with abundant submerged marginal vegetation (lowland and mangrove), the gears were rather efficient yielding excellent results when coupled with direct observation methods. Since the abiotic characteristics of a stream change longitudinally, it is appropriate to employ different methods in the study of the ichthyofauna composition and distribution in order to reduce the constraints imposed by sampling methods in running waters.

A composição e a distribuição espacial de uma comunidade de peixes foram estudadas em três trechos de um rio na costa leste do Brasil: um trecho de corredeiras (superior), um trecho de planície (médio) e outro de mangue (inferior). Dois métodos foram empregados com o objetivo de estimar sua eficiência em estudos naturalísticos de comunidades de peixes tropicais. Um dos métodos consiste em observações subaquáticas e o outro é caracterizado por capturas com o emprego de apetrechos, como covos, peneiras, vara e anzol. Os dois métodos mostraram que sua eficiência depende das características do ambiente e da biologia das espécies. Em trechos com elevada transparência da água, correnteza forte, substrato rochoso e sem vegetação marginal submersa (trecho superior), o emprego de equipamentos tradicionais é relativamente ineficiente, apesar de oferecer excelentes condições para observação subaquática. Em trechos com elevada transparência da água, correnteza forte e vegetação marginal submersa abundante (planície e mangue), os apetrechos de coleta oferecem bons resultados, principalmente se acoplados ao método de observação subaquática. Se as características abióticas do rio se alteram longitudinalmente, nos estudos acerca da composição e da distribuição da ictiofauna é apropriado o emprego de diferentes métodos de estudo, a fim de reduzir as falhas impostas pelas metodologias de coleta empregadas em ambientes de água corrente.

RESUMO

The species composition and spatial distribution of a fish assemblage were studied in three reaches of a river in the east coast of Brazil: a section of rapids (upper), another of water flowing on plain terrain (lowland) and the other of a mangrove environment. Two methods were employed with the purpose of estimating their effectiveness in naturalistic studies of tropical fish assemblages. One method consisted of underwater observations and the other was characterized by catches using gears such as fish traps, sieves and fishing rods. Both methods showed that their effectiveness is dependent upon the characteristics of the environment and the biology of the species. In areas of high water transparency and flow speed, rocky substrate and no submerged marginal vegetation (upper reach), the employment of the traditional gears was quite inefficient, despite the excellent conditions for underwater observations. In areas of clear water and high flow speed with abundant submerged marginal vegetation (lowland and mangrove), the gears were rather efficient yielding excellent results when coupled with direct observation methods. Since the abiotic characteristics of a stream change longitudinally, it is appropriate to employ different methods in the study of the ichthyofauna composition and distribution in order to reduce the constraints imposed by sampling methods in running waters

Assuntos

RESUMO

Many people in Amazonian communities have reported bat bites in the last decade. Bites by vampire bats can potentially transmit rabies to humans. The objective of this study was to analyze factors associated with bat biting in one of these communities. A cross-sectional survey was conducted in a village of gold miners in the Amazonian region of Brazil (160 inhabitants). Bats were captured near people's houses and sent to a lab. Of 129 people interviewed, 41% had been attacked by a bat at least once, with 92% of the bites located on the lower limbs. A logistic regression found that adults were bitten around four times more often than children (OR = 3.75, CI 95%: 1.46-9.62, p = 0.036). Males were bitten more frequently than females (OR = 2.08, CI 95%: 0.90-4.76, p = 0.067). Nine Desmodus rotundus and three frugivorous bats were captured and tested negative for rabies. The study suggests that, in an area of gold miners, common vampire bats are more likely to attack adults and males. The control strategy for human rabies developed in this region should therefore place special emphasis on adult males. There should also be more research on how the search for gold in the Amazonian region places people and the environment at risk.

Assuntos

RESUMO

The species composition and spatial distribution of a fish assemblage were studied in three reaches of a river in the east coast of Brazil: a section of rapids (upper), another of water flowing on plain terrain (lowland) and the other of a mangrove environment. Two methods were employed with the purpose of estimating their effectiveness in naturalistic studies of tropical fish assemblages. One method consisted of underwater observations and the other was characterized by catches using gears such as fish traps, sieves and fishing rods. Both methods showed that their effectiveness is dependent upon the characteristics of the environment and the biology of the species. In areas of high water transparency and flow speed, rocky substrate and no submerged marginal vegetation (upper reach), the employment of the traditional gears was quite inefficient, despite the excellent conditions for underwater observations. In areas of clear water and high flow speed with abundant submerged marginal vegetation (lowland and mangrove), the gears were rather efficient yielding excellent results when coupled with direct observation methods. Since the abiotic characteristics of a stream change longitudinally, it is appropriate to employ different methods in the study of the ichthyofauna composition and distribution in order to reduce the constraints imposed by sampling methods in running waters.

A composição e a distribuição espacial de uma comunidade de peixes foram estudadas em três trechos de um rio na costa leste do Brasil: um trecho de corredeiras (superior), um trecho de planície (médio) e outro de mangue (inferior). Dois métodos foram empregados com o objetivo de estimar sua eficiência em estudos naturalísticos de comunidades de peixes tropicais. Um dos métodos consiste em observações subaquáticas e o outro é caracterizado por capturas com o emprego de apetrechos, como covos, peneiras, vara e anzol. Os dois métodos mostraram que sua eficiência depende das características do ambiente e da biologia das espécies. Em trechos com elevada transparência da água, correnteza forte, substrato rochoso e sem vegetação marginal submersa (trecho superior), o emprego de equipamentos tradicionais é relativamente ineficiente, apesar de oferecer excelentes condições para observação subaquática. Em trechos com elevada transparência da água, correnteza forte e vegetação marginal submersa abundante (planície e mangue), os apetrechos de coleta oferecem bons resultados, principalmente se acoplados ao método de observação subaquática. Se as características abióticas do rio se alteram longitudinalmente, nos estudos acerca da composição e da distribuição da ictiofauna é apropriado o emprego de diferentes métodos de estudo, a fim de reduzir as falhas impostas pelas metodologias de coleta empregadas em ambientes de água corrente.

RESUMO

This is the first recorded case of rabies in the insectivorous bat Tadarida brasiliensis in the State of S. Paulo, Southeastern Brazil. The infected bat was found in the afternoon while hanging on the internal wall of an urban building. This observation reinforces the notion as to the caution one must exercise regarding bats found in unusual situations.

Assuntos

RESUMO

Human rabies transmitted by bats has acquired greater epidemiologic relevance in various Latin American countries, just when cases transmitted by dogs have decreased. Concern has been heightened by reports of increased rates of bats biting humans in villages in the Amazonian region of Brazil. The aim of the present work was to estimate the potential force of infection (per capita rate at which susceptible individuals acquire infection) of human rabies transmitted by the common vampire bat if the rabies virus were to be introduced to a colony of bats close to a village with a high rate of human bites. The potential force of infection could be then used to anticipate the size of a rabies outbreak in control programs. We present an estimator of potential incidence, adapted from models for malaria. To obtain some of the parameters for the equation, a cross-sectional survey was conducted in Mina Nova, a village of gold prospectors in the Amazonian region of Brazil with high rates of bates biting humans. Bats were captured near dwellings and sent to The Rabies Diagnostic Laboratory at the Center for Control of Zoonoses (Sao Paulo, Brazil) to be examined. To estimate the force of infection, a hypothetical rabies outbreak among bats was simulated using the actual data obtained in the study area. Of 129 people interviewed, 23.33% had been attacked by a vampire bat during the year prior to the study, with an average of 2.8 bites per attacked person. Males (29.41%) were attacked more often than females (11.36%); also, adults (29.35%) were attacked more often than children (8.33%). None of the 12 bats captured in Mina Nova tested positive for rabies, but the force of infection for a hypothetical outbreak was estimated to be 0.0096 per person per year. This risk represents 0.96 cases per 100 area residents, giving an incidence of 1.54 cases of bat-transmitted human rabies per year in the village of Mina Nova (160 inhabitants). The estimated risk is comparable with what has been observed in similar Brazilian villages.

Assuntos

RESUMO

Four rabid bats belonging to three species of Molossidae (one Molossus molossus, one Nyctinomops laticaudatus and two N. macrotis) were captured in the State of S. Paulo, southeastern Brazil. Three of these bats were found during the day in unusual, visible places and the other came flying through a window in the evening. A descriptive table containing data on 19 similar cases, belonging to eight species, is presented and suggests that bats with atypical behavior must dearly be suspected of being sick, possibly as having rabies.

Assuntos