Nature’s Miniature Compass: Desert Ants Use Earth’s Magnetic Field to Calibrate Their Navigation System

Navigating the environment is a challenging task that animals cope with daily. Some species demonstrate impressive capabilities to navigate in complex and harsh environments.

The Earth's magnetic field is an important navigational cue for many animals. However, the specific part of the brain where the magnetic field is processed is still little understood. In a recent study, researchers investigated the neuronal plasticity in the brain of Cataglyphis desert ants.

Calibrating Compass Systems

Desert ants have long been used as model species in studying animal navigation. These insects are only a few centimeters tall and have simple brain structures with less than a million neurons. Nevertheless, their ability to orient themselves to the Earth's magnetic field distinguishes them from other creatures.

This unique feature was discovered by a group of scientists from Julius-Maximilians-Universität Würzburg (JMU) a few years ago. In a new study, the experts investigated the specific part of the brain where the magnetic information is processed. Their findings are discussed in the paper "Navigation: How the Recent Past Shapes Future Routes in Desert Ants."

Professor Wolfgang Rössler led the research from the University of Würzburg, Dr. Pauline Fleischmann from the University of Oldenburg, and Dr. Robin Grob from the Norwegian University of Science and Technology. The field studies were conducted in southern Greece where the Cataglyphis ants are native. The team discovered that the information processing is primarily done in the ant's internal compass (central complex) and in the mushroom bodies (learning and memory centers).

Before a desert ant leaves its underground nest for the first time to search for food, it needs to calibrate its navigation system. Learning to walk starts by exploring its immediate surroundings around the nest entrance. Then, it repeatedly spins around its body axis with short stops in between. During such pauses, it always looks precisely back toward the nest entrance, even if the tiny hole in the ground is not visible.

Effect of Disrupted Magnetic Field

The researchers also studied the orientation behavior of the ants with the manipulated magnetic field. They focused on young workers who had not yet undertaken any learning walks. These insects were only allowed to set off as part of the precisely planned experiments, under natural conditions or in a permanently altered magnetic field.

The manipulated magnetic field either resulted in chaotic directions or did not allow horizontal orientation. The faulty information on the direction cannot be a reliable reference system for the ant's behavior to look back to the nest's entrance during the learning walks.

The neuroanatomical brain analyses also reveal that ants exposed to altered magnetic fields have a smaller volume and fewer synaptic complexes in the area of the brain responsible for integrating visual information and learning. The same findings were observed in the central complex, or the regions of the brain where spatial orientation is anchored.

In the future, the research team plans to investigate the sensory organ that receives the magnetic information and the sensory pathway where it is transmitted and processed.