Night sky orientation with diurnal and nocturnal eyes: dim-light adaptations are critical when the moon is out of sight

Smolka, Jochen; Baird, Emily; Jundi, Basil el; Reber, Therese; Byrne, Marcus J.; Dacke, Marie

doi:10.1016/j.anbehav.2015.10.005

Cited by 35 publications

(59 citation statements)

References 51 publications

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“…The distribution of the changes of direction was tested using a V-test with an expected mean of 08 or 1808. Similar to previous studies [3,11,13], the reliability of the V-test was analysed using permutation tests (electronic supplementary material, figure S1). Mardia -Watson -Wheeler tests were used to test for differences between circular data.…”

Section: (D) Data Analysismentioning

confidence: 99%

Spectral information as an orientation cue in dung beetles

et al. 2015

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During the day, a non-uniform distribution of long and short wavelength light generates a colour gradient across the sky. This gradient could be used as a compass cue, particularly by animals such as dung beetles that rely primarily on celestial cues for orientation. Here, we tested if dung beetles can use spectral cues for orientation by presenting them with monochromatic (green and UV) light spots in an indoor arena. Beetles kept their original bearing when presented with a single light cue, green or UV, or when presented with both light cues set 1808 apart. When either the UV or the green light was turned off after the beetles had set their bearing in the presence of both cues, they were still able to maintain their original bearing to the remaining light. However, if the beetles were presented with two identical green light spots set 1808 apart, their ability to maintain their original bearing was impaired. In summary, our data show that ball-rolling beetles could potentially use the celestial chromatic gradient as a reference for orientation.

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Section: (D) Data Analysismentioning

confidence: 99%

Spectral information as an orientation cue in dung beetles

et al. 2015

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“…In order to travel in a straight line, these species use celestial cues as compass references (Dacke et al ., 2011). In contrast to the closely related diurnal dung beetle Kheper lamarcki, E. satyrus orients to polarized light cues in preference to the observable position of the moon (el Jundi et al ., 2015a) and may be specialised to detect the faint lunar skylight that emanates from a crescent moon (Smolka et al ., 2016).…”

Section: Introductionmentioning

confidence: 99%

“…An assessment of the daytime skylight cues available near the crickets’ collection site, using an artificial polarization-sensitive “neuron”, suggested that degrees of polarization are typically quite low, as a result of haze and cloud cover, with median values of 0.13 and 0.23 in the solar and antisolar halves of the sky respectively (Labhart, 1999); as compared with values in excess of 0.60 measured in clear skies (Horváth et al ., 2014). While the low intensity of lunar skylight presents a challenge for the detection of polarized skylight at night, the superposition eyes of E. satyrus are well adapted to detect lunar skylight cues, and they orient well even under very dim conditions (Dacke et al ., 2011; Smolka et al ., 2016). Nevertheless, if the combination of moonlight with other, unpolarized, celestial light results in weakly-polarized skylight, then E. satyrus would require a degree-of-polarization threshold that is low enough to match the typical range found in its geographic distribution.…”

Section: Introductionmentioning

confidence: 99%

Orienting to Polarized Light at Night—Matching Lunar Skylight to Performance in a Nocturnal Beetle

Foster

Kirwan

Jundi

et al. 2018

Preprint

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A degree-of-polarization threshold for orientation behaviour is 15 reported for nocturnal dung beetle Escarabaeus satyrus in the context 16 of measurements showing changes in the degree of polarization of 17 skylight with lunar phase. 18 Abstract 19For polarized light to inform behaviour, the typical range of degrees of 20 polarization observable in the animal's natural environment must be 21 above the threshold for detection and interpretation. Here we present 22 the first investigation of the degree of linear polarization threshold for 23 orientation behaviour in a nocturnal species, with specific reference to 24 the range of degrees of polarization measured in the night sky. An 25 effect of lunar phase on the degree of polarization of skylight was 26 found, with smaller illuminated fractions of the moon's surface 27 corresponding to lower degrees of polarization in the night sky. We 28 found that South African dung beetle Escarabaeus satyrus 29 (Boheman, 1860) can orient to polarized light for a range of 30 degrees of polarization similar to that observed in diurnal insects, 31 reaching a lower threshold between 0.04 and 0.32, possibly as low as 32 2 0.11. For degrees of polarization lower than 0.23, as measured on a 33 crescent moon night, orientation performance was considerably 34 weaker than that observed for completely linearly-polarized stimuli, 35 but was nonetheless stronger than in the absence of polarized light. 36

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“…Nights can be chosen so that different features of the starry sky are visible, for example, so that the Milky Way crosses the zenith, or so that a particular asterism or bright star is visible or absent. Differences in weather conditions, such as overcast or partly cloudy skies, can act as a proxy for the availability of stellar cues by limiting the animal's view to fewer stars or obscuring them completely ( [11,33,45]; figure 2g -h). Further, stellar cues available from natural skies on clear nights can be manipulated by selective screening or optical adjustment of different sky regions.…”

Section: Testing Orientation Strategies (A) In Situ Experimentsmentioning

confidence: 99%

“…If the study animal compensates for latitudinal but not longitudinal displacements, then it may use the elevation of the centre of celestial rotation [9] or a specific line of declination [10] to judge latitude. If the study animal does not compensate for displacement, but remains oriented in the same direction as prior to displacement, it may use the centre of celestial rotation's azimuth [14] or another consistent feature of the sky's intensity profile [33,34] as a reference without compensating for the elevations of these features. If the study animal is only well oriented on one side of the geographical equator, it may rely on sky features specific to that hemisphere.…”

Section: (B) Geographical Displacementmentioning

confidence: 99%

How animals follow the stars

Foster

Smolka

Nilsson³

et al. 2018

Proc. R. Soc. B.

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Throughout history, the stars have provided humans with ever more information about our world, enabling increasingly accurate systems of navigation in addition to fuelling some of the greatest scientific controversies. What information animals have evolved to extract from a starry sky and how they do so, is a topic of study that combines the practical and theoretical challenges faced by both astronomers and field biologists. While a number of animal species have been demonstrated to use the stars as a source of directional information, the strategies that these animals use to convert this complex and variable pattern of dim-light points into a reliable 'stellar orientation' cue have been more difficult to ascertain. In this review, we assess the stars as a visual stimulus that conveys directional information, and compare the bodies of evidence available for the different stellar orientation strategies proposed to date. In this context, we also introduce new technologies that may aid in the study of stellar orientation, and suggest how field experiments may be used to characterize the mechanisms underlying stellar orientation.

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Night sky orientation with diurnal and nocturnal eyes: dim-light adaptations are critical when the moon is out of sight

Abstract: Night sky orientation with diurnal and nocturnal eyes: dim-light adaptations are critical when the moon is out of sight

Cited by 35 publications

References 51 publications

Spectral information as an orientation cue in dung beetles

Spectral information as an orientation cue in dung beetles

Orienting to Polarized Light at Night—Matching Lunar Skylight to Performance in a Nocturnal Beetle

How animals follow the stars

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