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A functional role of the sky's polarization pattern for orientation in the greater mouse-eared bat.

Greif S, Borissov I, Yovel Y, Holland RA - Nat Commun (2014)

Bottom Line: One such cue is the pattern of polarized light in the sky, which for example can be used by birds as a geographical reference to calibrate other cues in the compass mechanism.Here we demonstrate that the female greater mouse-eared bat (Myotis myotis) uses polarization cues at sunset to calibrate a magnetic compass, which is subsequently used for orientation during a homing experiment.This renders bats the only mammal known so far to make use of the polarization pattern in the sky.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK [2] Sensory Ecology Group, Max Planck Institute for Ornithology, Eberhard-Gwinner-Straße, 82319 Seewiesen, Germany.

ABSTRACT
Animals can call on a multitude of sensory information to orient and navigate. One such cue is the pattern of polarized light in the sky, which for example can be used by birds as a geographical reference to calibrate other cues in the compass mechanism. Here we demonstrate that the female greater mouse-eared bat (Myotis myotis) uses polarization cues at sunset to calibrate a magnetic compass, which is subsequently used for orientation during a homing experiment. This renders bats the only mammal known so far to make use of the polarization pattern in the sky. Although there is currently no clear understanding of how this cue is perceived in this taxon, our observation has general implications for the sensory biology of mammalian vision.

No MeSH data available.


Experimental boxes.On the left is the outer box (polarization box) with two different layers of filters. On the outside is a pseudo-depolarizing filter and on the inside a polarizing filter. The direction of polarization is indicated with arrows. On the right is the inner box (holding box) with its meshed windows.
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f2: Experimental boxes.On the left is the outer box (polarization box) with two different layers of filters. On the outside is a pseudo-depolarizing filter and on the inside a polarizing filter. The direction of polarization is indicated with arrows. On the right is the inner box (holding box) with its meshed windows.

Mentions: For the experiments, bats were put in holding cages at a treatment site 1.3 km away from their cave and offered a clear view of the horizon in all directions from 22 min before until 75 min after sunset (when the last visible post-sunset glow had disappeared). All experimental evenings generally had clear sky and always had a visible sunset with only the exceptional cloud coming up. Bats were placed in holding cages which consisted of an inner (120 × 120 × 63 mm) and outer (148 × 148 × 72 mm) cardboard box. The inner holding box had windows (98 × 47 mm) covered with plastic mesh (4 mm square). The outer experimental box also had windows (108 × 52 mm), covered with an outer layer of a pseudo-depolarizing filter (90% depolarization with a 10–15% reduction of light intensity for a range of 400–800 nm)6, effectively eliminating natural polarization. The windows further had an inner layer which was a polarizing filter (linear polarizer P500, 3Dlens Corporation Taiwan, ultraviolet block, transmittance: 43%, polarizing: efficiency 99.9% at 380–700 nm)2. The polarization direction of the inner filter was either vertically or horizontally oriented, with opposite sides having the same direction (Fig. 2). The boxes were oriented either with the vertically polarized windows 90° away from the sun (in a North–South axis), corresponding to the natural situation (PN), or they were shifted 90° so that now the horizontally polarized windows were oriented North–South (PS) (Fig. 1a). Bats were also kept in a double-wrapped magnetic Helmholtz coil with current antiparallel (resulting in no change of the natural magnetic field), as they served as a control group for another experiment (see Supplementary Data 1 for details of release nights).


A functional role of the sky's polarization pattern for orientation in the greater mouse-eared bat.

Greif S, Borissov I, Yovel Y, Holland RA - Nat Commun (2014)

Experimental boxes.On the left is the outer box (polarization box) with two different layers of filters. On the outside is a pseudo-depolarizing filter and on the inside a polarizing filter. The direction of polarization is indicated with arrows. On the right is the inner box (holding box) with its meshed windows.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109006&req=5

f2: Experimental boxes.On the left is the outer box (polarization box) with two different layers of filters. On the outside is a pseudo-depolarizing filter and on the inside a polarizing filter. The direction of polarization is indicated with arrows. On the right is the inner box (holding box) with its meshed windows.
Mentions: For the experiments, bats were put in holding cages at a treatment site 1.3 km away from their cave and offered a clear view of the horizon in all directions from 22 min before until 75 min after sunset (when the last visible post-sunset glow had disappeared). All experimental evenings generally had clear sky and always had a visible sunset with only the exceptional cloud coming up. Bats were placed in holding cages which consisted of an inner (120 × 120 × 63 mm) and outer (148 × 148 × 72 mm) cardboard box. The inner holding box had windows (98 × 47 mm) covered with plastic mesh (4 mm square). The outer experimental box also had windows (108 × 52 mm), covered with an outer layer of a pseudo-depolarizing filter (90% depolarization with a 10–15% reduction of light intensity for a range of 400–800 nm)6, effectively eliminating natural polarization. The windows further had an inner layer which was a polarizing filter (linear polarizer P500, 3Dlens Corporation Taiwan, ultraviolet block, transmittance: 43%, polarizing: efficiency 99.9% at 380–700 nm)2. The polarization direction of the inner filter was either vertically or horizontally oriented, with opposite sides having the same direction (Fig. 2). The boxes were oriented either with the vertically polarized windows 90° away from the sun (in a North–South axis), corresponding to the natural situation (PN), or they were shifted 90° so that now the horizontally polarized windows were oriented North–South (PS) (Fig. 1a). Bats were also kept in a double-wrapped magnetic Helmholtz coil with current antiparallel (resulting in no change of the natural magnetic field), as they served as a control group for another experiment (see Supplementary Data 1 for details of release nights).

Bottom Line: One such cue is the pattern of polarized light in the sky, which for example can be used by birds as a geographical reference to calibrate other cues in the compass mechanism.Here we demonstrate that the female greater mouse-eared bat (Myotis myotis) uses polarization cues at sunset to calibrate a magnetic compass, which is subsequently used for orientation during a homing experiment.This renders bats the only mammal known so far to make use of the polarization pattern in the sky.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK [2] Sensory Ecology Group, Max Planck Institute for Ornithology, Eberhard-Gwinner-Straße, 82319 Seewiesen, Germany.

ABSTRACT
Animals can call on a multitude of sensory information to orient and navigate. One such cue is the pattern of polarized light in the sky, which for example can be used by birds as a geographical reference to calibrate other cues in the compass mechanism. Here we demonstrate that the female greater mouse-eared bat (Myotis myotis) uses polarization cues at sunset to calibrate a magnetic compass, which is subsequently used for orientation during a homing experiment. This renders bats the only mammal known so far to make use of the polarization pattern in the sky. Although there is currently no clear understanding of how this cue is perceived in this taxon, our observation has general implications for the sensory biology of mammalian vision.

No MeSH data available.