Transfer of directional information between the polarization compass and the sun compass in desert ants

Abstract

Desert ants, Cataglyphis fortis, perform large foraging excursions during which they continuously compute a home vector that allows them to return to the nest on the shortest way. This type of navigation, termed path integration, needs a compass system and an odometer. Ants use several cues to determine their walking direction, two of the most important ones being the sun position and the polarization pattern of the sky. We tested whether an information transfer is possible from one compass system to the other, which depend on different anatomical substrates. Since the sky's polarization pattern is detected by UV-photoreceptors located in the dorsal rim area (DRA), we used an orange Perspex filter that eliminated the UV part of the spectrum to prevent the use of the polarization compass. The use of the sun compass could be excluded by appropriate screens. In the critical tests the ants had learned a nest-feeder direction with e.g. the sun compass only, and were later tested with the polarization compass, or vice versa. The results show that a transfer is possible in both directions.

A Snapshot-Based Mechanism for Celestial Orientation

“…We tested the underlying orientation mechanism by presenting beetles with a combination of simulated celestial cues (sun, polarized light, and spectral cues). We show that these animals do not rely on an innate prediction of the natural geographical relationship between celestial cues, as other navigating insects seem to [9,10]. Instead, they appear to form an internal representation of the prevailing celestial scene, a ''celestial snapshot,'' even if that scene represents a physical impossibility for the real sky.…”

“…According to the ''matched-filter'' model, all celestial cues could be linked together at the neural level, allowing the animal to swap easily between cues while navigating [16]. Indeed, desert ants (Cataglyphis fortis) appear to extrapolate the position of the sun by reading polarization information and thus seem to have an innate prediction of the natural geographical relationship of celestial cues [9,10]. To test whether dung beetles can transfer information from the sun compass to another celestial compass cue (e.g., from the sun to polarized light and vice versa), we first let the beetles roll with a green light as the only cue and then let them roll under only the polarized light (and vice versa).…”

The brain behind straight-line orientation in dung beetles

“…This undoubtedly allows the animal to identify the position of the sun from the polarization pattern. The same seems to hold true for Cataglyphis fortis ants, which readily switch from a sun to a polarization compass (Lebhardt and Ronacher, 2015). In addition, neurons in the locust brain give their greatest response in almost opposing directions, depending on whether they are stimulated with green light (relatively richer in the sun hemisphere) or UV light (relatively richer in the anti-sun hemisphere) (Pfeiffer and Homberg, 2007;Kinoshita et al, 2007).…”

Spatial orientation based on multiple visual cues in monarch butterflies

“…To obtain a robust orientation compass, it is well established that many insects use a combination of visual cues from their environment. Ants combine skylight (Lebhardt and Ronacher, 2015; Wehner, 1997) and terrestrial cues, such as the panoramic skyline (Collett and Collett, 2002; Durier et al, 2003; Graham and Cheng, 2009a; Judd and Collett, 1998), to define the desired homeward direction. Integration of multiple visual cues does not require a certain context (migration or homing) but is a common strategy of insects to keep track of their heading with respect to their environment, irrespective of their behavioral state.…”