RESUMO
Some bat species seem to be lunar phobic, i.e., they avoid flying in bright areas or during bright periods of the night; however, the evidence is still controversial. We think that part of this controversy comes from pooling data on bat captures and moonlight intensity according to broad categories, such as moon phases, which conceal the high variability among nights. Therefore, we used detailed, long-term field data on three phyllostomid bat species, in order to test the hypothesis of lunar phobia at two different time scales: 1) among nights, by pooling data of different nights according to moon phases and testing for differences in the distribution of captures; and 2) within a night, by analyzing the relationship between capturability and moonlight intensity (measured as illuminance) in one-hour intervals for 29 individual nights. Although most captures of the studied bat species occurred in the first half of the night, their activity pattern varied largely among nights, and was not always unimodal as commonly assumed. At the larger time scale, all studied bat species showed evidence of lunar phobia, as they were more frequently captured on dark moon phases. Nevertheless, at the smaller time scale, only Carollia perspicillata (Linnaeus, 1758) was less frequently captured on brighter periods of the night. We propose that the unimodal activity pattern assumed for frugivorous phyllostomid bats may be an artifact of data organization, and that activity and lunar phobia are much more variable than previously assumed.
RESUMO
Some bat species seem to be lunar phobic, i.e., they avoid flying in bright areas or during bright periods of the night; however, the evidence is still controversial. We think that part of this controversy comes from pooling data on bat captures and moonlight intensity according to broad categories, such as moon phases, which conceal the high variability among nights. Therefore, we used detailed, long-term field data on three phyllostomid bat species, in order to test the hypothesis of lunar phobia at two different time scales: 1) among nights, by pooling data of different nights according to moon phases and testing for differences in the distribution of captures; and 2) within a night, by analyzing the relationship between capturability and moonlight intensity (measured as illuminance) in one-hour intervals for 29 individual nights. Although most captures of the studied bat species occurred in the first half of the night, their activity pattern varied largely among nights, and was not always unimodal as commonly assumed. At the larger time scale, all studied bat species showed evidence of lunar phobia, as they were more frequently captured on dark moon phases. Nevertheless, at the smaller time scale, only Carollia perspicillata (Linnaeus, 1758) was less frequently captured on brighter periods of the night. We propose that the unimodal activity pattern assumed for frugivorous phyllostomid bats may be an artifact of data organization, and that activity and lunar phobia are much more variable than previously assumed.
RESUMO
Some bat species seem to be lunar phobic, i.e., they avoid flying in bright areas or during bright periods of the night; however, the evidence is still controversial. We think that part of this controversy comes from pooling data on bat captures and moonlight intensity according to broad categories, such as moon phases, which conceal the high variability among nights. Therefore, we used detailed, long-term field data on three phyllostomid bat species, in order to test the hypothesis of lunar phobia at two different time scales: 1) among nights, by pooling data of different nights according to moon phases and testing for differences in the distribution of captures; and 2) within a night, by analyzing the relationship between capturability and moonlight intensity (measured as illuminance) in one-hour intervals for 29 individual nights. Although most captures of the studied bat species occurred in the first half of the night, their activity pattern varied largely among nights, and was not always unimodal as commonly assumed. At the larger time scale, all studied bat species showed evidence of lunar phobia, as they were more frequently captured on dark moon phases. Nevertheless, at the smaller time scale, only Carollia perspicillata (Linnaeus, 1758) was less frequently captured on brighter periods of the night. We propose that the unimodal activity pattern assumed for frugivorous phyllostomid bats may be an artifact of data organization, and that activity and lunar phobia are much more variable than previously assumed.
RESUMO
Understanding what influences the activity of organisms is important for both ecological understanding and species conservation. Using data from 2,707 camera trap days distributed across 24 forest sites, we present quantitative analyses of the activity pattern of Cuniculus paca (Linnaeus, 1766) in southern Amazonia. We compared the activity pattern of this species across four designated subsets of the 24-hours diel cycle (dawn, dusk, day and night). Using linear regression models we tested the influence of season, temperature and rainfall on the activity patterns of C. paca (paca). We also evaluated the nocturnal photos of paca (N = 111) as a function of the degree of lunar illumination in order to test the prediction that pacas minimize their activity during moon phase when illumination is brighter. Pacas were not recorded during the day but were active at dawn, dusk and night time. We found differences in the influence of the abiotic variables on the nocturnal activity of pacas in the study area. There was no significant difference between the observed (expressed as the frequency of total counts of independent photos over the five classes of lunar illumination) and the expected activity of pacas, based on the frequency of days in the lunar cycle with different classes of lunar illumination, whereas lunar illumination had a weak negative influence on the timing of paca activity (i.e. pacas were active closer to sunset with increasing lunar illumination). However, the timing of nocturnal activity in pacas was not influenced by season, temperature or rainfall. Our findings highlight the ecological plasticity of this Neotropical rodent which has a key function in the maintenance of Neotropical forests.
RESUMO
The moonlights influence on bats activity patterns have been documented for some species. Usually, bats react to increased illumination by reducing the use of open spaces or restricting foraging activity. This study aimed to test lunar cycle influence on frequency of Phyllostomidae bats in three fragments, located in northwestern São Paulo State, analyze the capture rate in the different phases of the cycle and correlate the results with canopy structure of each remaining. This study was based on the on the assumption that the influence of light on the behavior of bats is lower in shaded areas. The decrease in species richness in relation to the moon phase was significant in the least shaded area. In environments with more closed canopy, the rate of capture of bats was homogeneous along the four phases of the moon. The results indicated that local wealth cannot be sampled effectively if the catches are restricted to any period of the lunar cycle for fruit and nectar, and in more shaded environments the effects of lunar phobia is apparently null.
A influência do reflexo da luz do sol pela lua no padrão de atividade de morcegos já foi documentada para algumas espécies. Geralmente os morcegos reagem ao aumento da iluminação reduzindo o uso de espaços abertos ou restringindo a atividade de forrageio. O objetivo deste estudo foi testar a influência do ciclo lunar sobre a freqüência de morcegos Phyllostomidae em três remanescentes florestais localizados no noroeste do Estado de São Paulo, analisando a taxa de captura nas diferentes fases do ciclo, além de relacionar os resultados com a estrutura do dossel de cada remanescente. Este estudo foi embasado na hipótese de que quanto maior é o sombreamento vegetal, menor seria a influência da luminosidade no comportamento destes indivíduos. A diminuição da riqueza de espécies em relação às fases da lua foi significativa no ambiente menos sombreado. Em ambientes com o dossel mais fechado, a taxa de captura de morcegos foi similar ao longo das quatro fases da lua. Os resultados indicaram que a riqueza local não pode ser amostrada de forma eficaz se as capturas forem restritas a qualquer período do ciclo lunar para frugívoros e nectarívoros, e que em ambientes mais sombreados o efeito da fobia lunar aparentemente é nulo.
RESUMO
The moonlights influence on bats activity patterns have been documented for some species. Usually, bats react to increased illumination by reducing the use of open spaces or restricting foraging activity. This study aimed to test lunar cycle influence on frequency of Phyllostomidae bats in three fragments, located in northwestern São Paulo State, analyze the capture rate in the different phases of the cycle and correlate the results with canopy structure of each remaining. This study was based on the on the assumption that the influence of light on the behavior of bats is lower in shaded areas. The decrease in species richness in relation to the moon phase was significant in the least shaded area. In environments with more closed canopy, the rate of capture of bats was homogeneous along the four phases of the moon. The results indicated that local wealth cannot be sampled effectively if the catches are restricted to any period of the lunar cycle for fruit and nectar, and in more shaded environments the effects of lunar phobia is apparently null.
A influência do reflexo da luz do sol pela lua no padrão de atividade de morcegos já foi documentada para algumas espécies. Geralmente os morcegos reagem ao aumento da iluminação reduzindo o uso de espaços abertos ou restringindo a atividade de forrageio. O objetivo deste estudo foi testar a influência do ciclo lunar sobre a freqüência de morcegos Phyllostomidae em três remanescentes florestais localizados no noroeste do Estado de São Paulo, analisando a taxa de captura nas diferentes fases do ciclo, além de relacionar os resultados com a estrutura do dossel de cada remanescente. Este estudo foi embasado na hipótese de que quanto maior é o sombreamento vegetal, menor seria a influência da luminosidade no comportamento destes indivíduos. A diminuição da riqueza de espécies em relação às fases da lua foi significativa no ambiente menos sombreado. Em ambientes com o dossel mais fechado, a taxa de captura de morcegos foi similar ao longo das quatro fases da lua. Os resultados indicaram que a riqueza local não pode ser amostrada de forma eficaz se as capturas forem restritas a qualquer período do ciclo lunar para frugívoros e nectarívoros, e que em ambientes mais sombreados o efeito da fobia lunar aparentemente é nulo.
RESUMO
Understanding what influences the activity of organisms is important for both ecological understanding and species conservation. Using data from 2,707 camera trap days distributed across 24 forest sites, we present quantitative analyses of the activity pattern of Cuniculus paca (Linnaeus, 1766) in southern Amazonia. We compared the activity pattern of this species across four designated subsets of the 24-hours diel cycle (dawn, dusk, day and night). Using linear regression models we tested the influence of season, temperature and rainfall on the activity patterns of C. paca (paca). We also evaluated the nocturnal photos of paca (N = 111) as a function of the degree of lunar illumination in order to test the prediction that pacas minimize their activity during moon phase when illumination is brighter. Pacas were not recorded during the day but were active at dawn, dusk and night time. We found differences in the influence of the abiotic variables on the nocturnal activity of pacas in the study area. There was no significant difference between the observed (expressed as the frequency of total counts of independent photos over the five classes of lunar illumination) and the expected activity of pacas, based on the frequency of days in the lunar cycle with different classes of lunar illumination, whereas lunar illumination had a weak negative influence on the timing of paca activity (i.e. pacas were active closer to sunset with increasing lunar illumination). However, the timing of nocturnal activity in pacas was not influenced by season, temperature or rainfall. Our findings highlight the ecological plasticity of this Neotropical rodent which has a key function in the maintenance of Neotropical forests.
RESUMO
Understanding what influences the activity of organisms is important for both ecological understanding and species conservation. Using data from 2,707 camera trap days distributed across 24 forest sites, we present quantitative analyses of the activity pattern of Cuniculus paca (Linnaeus, 1766) in southern Amazonia. We compared the activity pattern of this species across four designated subsets of the 24-hours diel cycle (dawn, dusk, day and night). Using linear regression models we tested the influence of season, temperature and rainfall on the activity patterns of C. paca (paca). We also evaluated the nocturnal photos of paca (N = 111) as a function of the degree of lunar illumination in order to test the prediction that pacas minimize their activity during moon phase when illumination is brighter. Pacas were not recorded during the day but were active at dawn, dusk and night time. We found differences in the influence of the abiotic variables on the nocturnal activity of pacas in the study area. There was no significant difference between the observed (expressed as the frequency of total counts of independent photos over the five classes of lunar illumination) and the expected activity of pacas, based on the frequency of days in the lunar cycle with different classes of lunar illumination, whereas lunar illumination had a weak negative influence on the timing of paca activity (i.e. pacas were active closer to sunset with increasing lunar illumination). However, the timing of nocturnal activity in pacas was not influenced by season, temperature or rainfall. Our findings highlight the ecological plasticity of this Neotropical rodent which has a key function in the maintenance of Neotropical forests.
RESUMO
The influence of moonlight on the activity patterns of bats has been reported to some species. In general, bats react to the increase of nocturnal illumination by reducing the use of open spaces, by limiting foraging activity or by shortening the activity periods. To determine the influence of moon cycle on the efficiency of bat netting, captures of 28 night-samplings were analyzed in southeastern Brazil. The capture rate and species richness were inversely related to the moonlight intensity. Among the most frequently netted species, only two showed significant and negative relation with increasing moonlight. The highest variation in species richness was observed in gleaners and nectarivorous species. The days following new moon were the most productive in terms of capture rate and species richness. The local species richness was not archived when sampling was restricted to any single period of the moon cycle. Bat community studies may benefit from samplings spanning the entire moon cycle.
A influência da luz da lua no padrão de atividade de morcegos já foi documentada em algumas espécies. Geralmente os morcegos reagem ao aumento da iluminação reduzindo o uso de espaços abertos e restringindo a atividade de forrageio ou a duração do período de atividade. Para estabelecer a influência do ciclo lunar na eficiência de captura de morcegos, foi realizada uma análise com 28 noites de capturas no sudeste do Brasil. A taxa de captura e a riqueza de espécies apresentaram relação linear inversa com a porção iluminada pela lua. Das espécies mais freqüentemente capturadas, apenas duas apresentaram relação significativa e negativa com o aumento da iluminação pela lua. Maiores variações na riqueza de espécies foram observadas em morcegos catadores e nectarívoros. Os dias após a lua nova são os mais produtivos em relação a capturas e riqueza. A riqueza local não pode ser totalmente amostrada se a amostragem for restrita a qualquer período do ciclo lunar. Para estudar a comunidade de morcegos é mais apropriado realizar amostragem durante todo o ciclo lunar.
RESUMO
The influence of moonlight on the activity patterns of bats has been reported to some species. In general, bats react to the increase of nocturnal illumination by reducing the use of open spaces, by limiting foraging activity or by shortening the activity periods. To determine the influence of moon cycle on the efficiency of bat netting, captures of 28 night-samplings were analyzed in southeastern Brazil. The capture rate and species richness were inversely related to the moonlight intensity. Among the most frequently netted species, only two showed significant and negative relation with increasing moonlight. The highest variation in species richness was observed in gleaners and nectarivorous species. The days following new moon were the most productive in terms of capture rate and species richness. The local species richness was not archived when sampling was restricted to any single period of the moon cycle. Bat community studies may benefit from samplings spanning the entire moon cycle.
A influência da luz da lua no padrão de atividade de morcegos já foi documentada em algumas espécies. Geralmente os morcegos reagem ao aumento da iluminação reduzindo o uso de espaços abertos e restringindo a atividade de forrageio ou a duração do período de atividade. Para estabelecer a influência do ciclo lunar na eficiência de captura de morcegos, foi realizada uma análise com 28 noites de capturas no sudeste do Brasil. A taxa de captura e a riqueza de espécies apresentaram relação linear inversa com a porção iluminada pela lua. Das espécies mais freqüentemente capturadas, apenas duas apresentaram relação significativa e negativa com o aumento da iluminação pela lua. Maiores variações na riqueza de espécies foram observadas em morcegos catadores e nectarívoros. Os dias após a lua nova são os mais produtivos em relação a capturas e riqueza. A riqueza local não pode ser totalmente amostrada se a amostragem for restrita a qualquer período do ciclo lunar. Para estudar a comunidade de morcegos é mais apropriado realizar amostragem durante todo o ciclo lunar.
RESUMO
The nightly activity patterns of Noctilio leporinus, a piscivorous neotropical bat, were documented by visual observation over one lunar cycle at a large dock in Golfito, Costa Rica. The activity patterns were compared to the intensity of the moonlight, and a strong correlation between darkness and activity was observed (n = 776, r2 = 0.96). This correlation has been observed in many species of mammals and may indicate adaptation by potential prey species to avoid predation by visually oriented nighttime predators and/or an adaptation by predators to maximize hunting success.
Documenté los patrones de actividad nocturna de Noctilio leporinus, murciélago piscívoro neotropical, mediante observaciones visuales durante un ciclo lunar en un muelle de Golfito, Costa Rica. Considerando la intensidad de la luz lunar, hubo una fuerte correlación entre la oscuridad y la actividad (n = 776, r2 = 0.96). Esta correlación ha sido observada en muchas especies de mamíferos y puede indicar una adaptación de presas potenciales para evadir los depredadores nocturnos y/o una adaptación de los depredadores para maximizar el éxito de cacería.