RESUMO

Human disturbances affect the macroinvertebrate populations in coastal regions. They respond to disturbances by altering their density and behaviour. Therefore, many of them are used as bioindicator species of human disturbance. Here, we pioneer the use of fiddler crabs to examine whether they alter their behaviour under human disturbance. Male fiddler crabs possess one large claw used for courting (waving) and fighting, and one small feeding claw, whereas females have two feeding claws. They show several surface activities. This study investigates (1) the effects of human disturbance on density and sex-ratio, and (2) the effects of human disturbance, and sex on behavioural time allocations in Austruca annulipes. Their density, sex-ratio, and time allocations were investigated in human-disturbed area (DA) and nondisturbed area (NDA). They showed feeding, feeding and walking, walking, running, standing/vigilance, inside burrows, burrowing, grooming, fighting, and waving. The results showed that crab density was higher and the sex ratio was more male biased in NDA than in DA. Human disturbance and sex affected time allocations but their interaction had no effect. Crabs in DA spent more time running, standing, and inside burrows but less time walking, burrowing, fighting, and waving than crabs in NDA. Between sexes, males spent more time standing, burrowing, grooming, and fighting but less time feeding, and walking than females. This indicates that human disturbances force the crabs to spend more time on anti-predator and escape behavior (standing/vigilance, running, inside burrows) rather than courting (waving) and constructing burrows (mating/breeding sites), which are important for breeding.(AU)

Assuntos

RESUMO

Inter-temporal trade-offs are ubiquitous in human decision making. We study the relationship between preferences over such trade-offs and the ratio of the second digit to that of the forth (2D:4D), a marker for pre-natal exposure to sex hormones. Specifically, we study whether 2D:4D affects discounting. Our sample consists of 419 female participants of a Guatemalan conditional cash transfer program who take part in an experiment. Their choices in the convex time budget (CTB) experimental task allow us to make inferences regarding their patience (discounting), while controlling for present-biasedness and preference for smoothing consumption (utility curvature). We find that women with lower digit ratios tend to be more patient.

RESUMO

Sunset and sunrise regulate the activities of most studied bat species. To verify patterns of foraging activity, 29 bat sampling nights were carried out over a dam in Rio de Janeiro city, which resulted in 363 hours with 730 captures, representing 13 species of insectivorous bats. Molossus molossus constituted the bulk of the captures (79.9 percent) and was present in 82.8 percent of the sampling nights. This bat species exhibited crepuscular and nocturnal activity (from -6 minutes to 900 minutes after the time of sunset). A bimodal activity pattern was observed, and two non-overlapping capture peaks. The first peak lasted from 6 minutes before sunset to 420 minutes after sunset. The second peak began at 564 minutes after sunset and ended just after sunrise. The first capture peak was observed in 75.9 percent of the nights, and the second peak in 62.1 percent of the nights. The time of the first capture exhibited a positive linear relationship with sunset and the time of the last capture, a positive linear relationship with sunrise. The existence of a relationship between night length and the difference between first and last captures of each night shows that M. molossus has longer activity the longer the night, showing a seasonal variation in the activity period.

A atividade dos morcegos inicia-se imediatamente antes, durante ou imediatamente após o pôr do sol. O início e o término das atividades dos morcegos são reguladas respectivamente pelo pôr e nascer do sol. Nesse trabalho, 29 noites de amostragem foram realizadas (total de 363 horas) sobre um açude na Cidade do Rio de Janeiro para avaliar a atividade de forrageio de Molossus molossus. Esse esforço resultou em 730 capturas de 13 espécies de morcegos insetívoros. Molossus molossus constituiu a maior parte das capturas e representou 79,9 por cento da amostragem, presente em 82,8 por cento das noites de coleta. Esta espécie apresenta atividade crepuscular e noturna (de -6 minutes a 900 minutos após o pôr do sol). Foi observado um padrão bimodal de atividade com picos de capturas sem superposição, sendo o primeiro 6 minutos antes do pôr do sol a 420 minutos após o pôr do sol, e o segundo aos 564 minutos após o pôr do sol e término imediatamente após o nascer do sol. O primeiro pico de captura ocorreu em 75,9 por cento das noites e o segundo em 62,1 por cento das noites. O horário da primeira captura resultou em uma relação linear positiva com o pôr do sol e o horário da última captura, com o nascer do sol. A existência de relação entre a duração da noite e a diferença entre a primeira e a última captura de cada noite demonstra que M. molossus tem maior período de atividade quanto mais longa é a noite, sustentando uma variação estacional do período de atividade.

Assuntos

RESUMO

Sunset and sunrise regulate the activities of most studied bat species. To verify patterns of foraging activity, 29 bat sampling nights were carried out over a dam in Rio de Janeiro city, which resulted in 363 hours with 730 captures, representing 13 species of insectivorous bats. Molossus molossus constituted the bulk of the captures (79.9%) and was present in 82.8% of the sampling nights. This bat species exhibited crepuscular and nocturnal activity (from -6 minutes to 900 minutes after the time of sunset). A bimodal activity pattern was observed, and two non-overlapping capture peaks. The first peak lasted from 6 minutes before sunset to 420 minutes after sunset. The second peak began at 564 minutes after sunset and ended just after sunrise. The first capture peak was observed in 75.9% of the nights, and the second peak in 62.1% of the nights. The time of the first capture exhibited a positive linear relationship with sunset and the time of the last capture, a positive linear relationship with sunrise. The existence of a relationship between night length and the difference between first and last captures of each night shows that M. molossus has longer activity the longer the night, showing a seasonal variation in the activity period.

A atividade dos morcegos inicia-se imediatamente antes, durante ou imediatamente após o pôr do sol. O início e o término das atividades dos morcegos são reguladas respectivamente pelo pôr e nascer do sol. Nesse trabalho, 29 noites de amostragem foram realizadas (total de 363 horas) sobre um açude na Cidade do Rio de Janeiro para avaliar a atividade de forrageio de Molossus molossus. Esse esforço resultou em 730 capturas de 13 espécies de morcegos insetívoros. Molossus molossus constituiu a maior parte das capturas e representou 79,9% da amostragem, presente em 82,8% das noites de coleta. Esta espécie apresenta atividade crepuscular e noturna (de -6 minutes a 900 minutos após o pôr do sol). Foi observado um padrão bimodal de atividade com picos de capturas sem superposição, sendo o primeiro 6 minutos antes do pôr do sol a 420 minutos após o pôr do sol, e o segundo aos 564 minutos após o pôr do sol e término imediatamente após o nascer do sol. O primeiro pico de captura ocorreu em 75,9% das noites e o segundo em 62,1% das noites. O horário da primeira captura resultou em uma relação linear positiva com o pôr do sol e o horário da última captura, com o nascer do sol. A existência de relação entre a duração da noite e a diferença entre a primeira e a última captura de cada noite demonstra que M. molossus tem maior período de atividade quanto mais longa é a noite, sustentando uma variação estacional do período de atividade.