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

Bats using echolocation for orientation in space and for foraging rely on the information provided by the echoes of their emitted signals. In the presence of conspecifics, signals of individuals may overlap in time and frequency and may impede the bats ability to process their own echo information. Adjustment of echolocation signal parameters as a mechanism to minimize the effects of signal overlap has been proposed for bats. We conducted a field study in Panama, confronting free-flying Greater bulldog bats Noctilio leporinus (Noctilionidae) with playbacks of conspecific search signals that matched the constant-frequency (QCF) signal component of the bats expected echo. Additionally, we recorded echolocation signals of bats flying in pairs to compare the results of our playback experiments with bats encountering conspecifics under natural conditions. Noctilio leporinus did not shift the frequency of its QCF components, neither when confronted with our playbacks nor in the presence of conspecifics. We discuss modifications of signal parameters and foraging behavior as strategies to avoid masking situations in N. leporinus.

Assuntos

Animais , Ecolocação , Orientação , Quirópteros , Comportamento Animal

RESUMO

Bats using echolocation for orientation in space and for foraging rely on the information provided by the echoes of their emitted signals. In the presence of conspecifics, signals of individuals may overlap in time and frequency and may impede the bats ability to process their own echo information. Adjustment of echolocation signal parameters as a mechanism to minimize the effects of signal overlap has been proposed for bats. We conducted a field study in Panama, confronting free-flying Greater bulldog bats Noctilio leporinus (Noctilionidae) with playbacks of conspecific search signals that matched the constant-frequency (QCF) signal component of the bats expected echo. Additionally, we recorded echolocation signals of bats flying in pairs to compare the results of our playback experiments with bats encountering conspecifics under natural conditions. Noctilio leporinus did not shift the frequency of its QCF components, neither when confronted with our playbacks nor in the presence of conspecifics. We discuss modifications of signal parameters and foraging behavior as strategies to avoid masking situations in N. leporinus.(AU)

Assuntos

Animais , Quirópteros , Ecolocação , Orientação , Comportamento Animal

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.