The Geomagnetic Field Is a Compass Cue in Cataglyphis Ant Navigation

Abstract

Desert ants (Cataglyphis) are famous insect navigators. During their foraging lives, the ants leave their underground colonies for long distances and return to their starting point with fair accuracy [1, 2]. Their incessantly running path integrator provides them with a continually updated home vector [3-5]. Directional input to their path integrator is provided by a visual compass based on celestial cues [6, 7]. However, as path integration is prone to cumulative errors, the ants additionally employ landmark guidance routines [8-11]. At the start of their foraging lives, they acquire the necessary landmark information by performing well-structured learning walks [12, 13], including turns about their vertical body axes [14]. When Cataglyphis noda performs these pirouettes, it always gazes at the nest entrance during the longest of several short stopping phases [14]. As the small nest entrance is not visible, the ants can adjust their gaze direction only by reading out their path integrator. However, recent experiments have shown that, for adjusting the goal-centered gaze directions during learning walks, skylight cues are not required [15]. A most promising remaining compass cue is the geomagnetic field, which is used for orientation in one way or the other by a variety of animal species [16-25]. Here, we show that the gaze directions during the look-back-to-the-nest behavior change in a predictable way to alterations of the horizontal component of the magnetic field. This is the first demonstration that, in insects, a geomagnetic compass cue is both necessary and sufficient for accomplishing a well-defined navigational task.

Path integration: how details of the honeybee waggle dance and the foraging strategies of desert ants might help in understanding its mechanisms

“…A recent example of PI operating in unfamiliar surroundings comes from a study of desert ants (Cataglyphis nodus) embarking on a foraging career. When these novices leave their nest for the first time, they memorise the arrangement of surrounding visual features so that they can find their way back home (Fleischmann et al, 2018). They do so in what are called 'learning walks,' in which ants circle the nest, periodically turning towards and facing the nest entrance, presumably acquiring views that can guide their return.…”

“…They do so in what are called 'learning walks,' in which ants circle the nest, periodically turning towards and facing the nest entrance, presumably acquiring views that can guide their return. Experiments in which the direction of the magnetic field was shifted in the immediate vicinity of the nest showed that the ants tracked the direction of the nest using PI, with the Earth's magnetic field as a compass (Fleischmann et al, 2018). These young ants may rely on magnetic cues, despite the presence of conflicting celestial cues, because they have not yet learnt how the sun moves through the sky (Grob et al, 2017).…”

A simple mathematical model using centred loops and random perturbations accurately reconstructs search patterns observed in desert ants

“…Collett et al 1998; Wehner and Wehner 1986; Wehner 2003; see also Mangan and Webb 2012 for C. velox ). Other cues that help them navigate are olfactory stimuli (Steck et al 2009), surface structure (Merkle 2009), or tactile (Seidl and Wehner 2006) and magnetic cues (Fleischmann et al 2018). These various systems are not thought to be switched on or off sequentially, but to operate in parallel at all times (Wehner et al 2016).…”

Kompass im Kopf

“…Zu unserer großen Überraschung haben naive Ameisen selbst nach der Blockierung des Polarisationsmusters und der Sonnenposition (d. h. ohne Himmelskompass) problemlos zum Nesteingang ausgerichtete Stopps ausgeführt. Wir fragten uns, ob die Ameisen vielleicht das ▸ Erdmagnetfeld nutzen können . Um diese Vermutung zu überprüfen, führten wir einen Versuch mit einer elektromagnetischen Flachspule, die wir um den Nesteingang legten, durch.…”