The Dynamics of Geomagnetic and Celestial Compass Cues in Cataglyphis Ant Navigation

• Applicant: Dr. Pauline Fleischmann
• Subject Area: Sensory and Behavioural Biology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 422729997

Successful navigation is a challenging task for all mobile animals. Cataglyphis ants are famous experimental models for navigation by means of path integration (PI). Solitary foragers leave the nest entrance – a tiny hole invisible from the ant’s perspective – to search for food. After finding prey, they return to the nest in a straight line. Foragers determine their directions travelled by relying on celestial compass cues (e.g. the polarization pattern or the sun’s position) and measure their distances travelled by using an innate odometer. Besides Cataglyphis’ impressive navigational performance during foraging, these ants show another striking behavior – so-called learning walks (LWs) – at the beginning of their foraging careers. LWs are short, explorative trips around the nest entrance during which ants do not collect any food, but acquire all information necessary to become foragers. Before the first extensive foraging trip, ants perform several LWs to learn the landmark panorama and to calibrate their compass systems. LWs include pirouettes, i.e. full or partial turns about the ant’s vertical axis that are frequently interrupted by stopping phases. During the longest stop ants gaze back to the nest entrance presumably to memorize the homing direction. Recently, it has been shown that Cataglyphis ants use the earth’s magnetic field as a compass cue to align their gaze directions during LW pirouettes. Therefore, Cataglyphis ants use at least two different compass systems, i.e. a celestial compass and a magnetic compass, to navigate by means of PI. Celestial compass cues have to be initially calibrated as they show seasonal and geographical variation. In contrast, the earth’s magnetic field offers a geostable reference system that is in principle already available in the dark nest. The key question – why do Cataglyphis ants possess two different compass systems for PI and how are these two systems linked? – is the starting point of the current project. First, we want to investigate the newly-discovered magnet compass in more detail by performing behavioral manipulation experiments in the field. Secondly, we will compare naïve LWs with re-learning walks of foragers in the natural habitat and the lab using high-speed video recordings. Finally, we aim to understand the role of geomagnetic and celestial cues during LWs on the behavioral and the neuronal level. We expect valuable insights into the functioning of the newly-discovered magnet compass of Cataglyphis, into the dynamic use of two compass cues both used for PI, and into the neuronal basis underlying Cataglyphis’ navigational performance. These results will be crucial progress for two as yet mostly separate research areas, i.e. neuroethology of insect navigation and sensory biology of magnetoception, and may act as the beginning of a new line of research.

• DFG Programme: Research Grants