Aerial-hawking bats adjust their use of space to the lunar cycle

Manuel Roeleke,Tobias Teige,Christian C Voigt,Uwe Hoffmeister,Friederike Klingler

doi:10.1186/s40462-018-0131-7

Manuel Roeleke, Tobias Teige + Show 3 more

Open Access

https://doi.org/10.1186/s40462-018-0131-7

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Abstract

BackgroundAnimals change their habitat use in response to spatio-temporal fluctuation of resources. Some resources may vary periodically according to the moonphase. Yet it is poorly documented how animals, particularly nocturnal mammals, adjust their use of space in response to the moonphase.Here, we asked if an obligate nocturnal mammal, the aerial-hawking common noctule bat (Nyctalus noctula), adjusts its 3-dimensional flight behaviour and habitat use to the lunar period. Using miniaturized GPS loggers, we recorded 3-dimensional flight tracks of N. noctula and related these to a canopy height model derived from aerial laser scans to investigate whether bats adjust forest strata use to moonlight intensities.ResultsNoctules frequently foraged above the canopy of coniferous forest at low moonlight intensities, but switched to using open grasslands and arable fields in nights with high moonlight intensities. During the few occasions when noctules used the forest during moonlit nights, they mostly restricted their use of space to flying below the canopy level. The median overall flight altitude of N. noctula equalled 13 ± 16 m but reached up to 71 m above ground (97.5% quantile).ConclusionsOur findings argue against general lunar phobic behaviour of aerial-hawking bats. We suggest that the preferred use of open fields around full moon may be a strategy of noctules to increase the success of hunting airborne insects at night. Specifically, the adjustment in use of space may allow bats to hunt for insects that emerge and disperse over open fields during bright moonlight.

Highlights

Animals change their habitat use in response to spatio-temporal fluctuation of resources
Moonlight and flight altitude The median overall flight altitude of N. noctula equalled 13 ± 16 m, but reached up to 71 m above the ground (97.5% quantile). This corresponded to a maximum altitude of 63 m above the canopy level (97.5% quantile) when noctules flew above forested areas In general, N. noctula flew at lower altitudes during high than during low moonlight intensities, except when flying above urban areas (Fig. 1, Table 1)
The recorded movement behaviour suggests that bats used the water bodies mainly for foraging (Fig. 4, in total 67% of the Global positioning system (GPS) locations over water were classified as foraging)

Summary

Introduction

Animals change their habitat use in response to spatio-temporal fluctuation of resources. Some resources may vary periodically according to the moonphase It is poorly documented how animals, nocturnal mammals, adjust their use of space in response to the moonphase. We asked if an obligate nocturnal mammal, the aerial-hawking common noctule bat (Nyctalus noctula), adjusts its 3-dimensional flight behaviour and habitat use to the lunar period. Animals live in heterogeneous landscapes that offer resources for different requirements, such as breeding, shelter, or foraging [1] Such functional heterogeneity within landscapes may occur in space and time alike [2]. According to the optimal foraging theory [10], animals should react towards periodic and predictable temporal heterogeneity in habitat suitability with a concordant adjustment of their use of space

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