A team of researchers designed an air-cushioned spherical treadmill for studying the navigational abilities of animals. Their newly developed tool was used to record the behaviors of desert ants as they navigated to and from their nest. The details are in a paper that was just published in the Journal of Experimental Biology.
Treadmills have long been used to study the walking and navigational behaviors of animals. Spherical treadmills are particularly useful—the animals generally walk in a natural manner without actually going anywhere. Although spherical treadmills originally had very simple designs, they have become more sophisticated with time. A recent version used an air-cushioned sphere with a contrasting pattern that helped a nearby camera track movements. The problem is that both the pattern and lighting needed to be perfect for precise tracking, limiting the accuracy of measurements.
Scientists from the University of Freiburg in Germany designed a simple but improved version of the spherical treadmill. Their design consists of a lightweight styrofoam ball with a tether that is held up by streams of air. Instead of a camera, optical mouse sensors are used to track movements. The research team tested their device with desert ants (Cataglyphis), insects that are capable of navigating perfectly through the desert without relying on landmarks.
The spherical treadmill worked well for tracking the movements and orientation of the studied desert ants. The team learned that the ants change their walking speed when returning to the nest. They initially walk very fast in a direct path but then slow down while searching for the exact spot. This information was new to the researchers, providing an example of how the spherical treadmill could be used in future experiments.
The team’s findings provide new insights into the navigational abilities of desert ants. The study also highlights a new spherical treadmill design that may aid other research teams that are studying animal navigation and movement.
Dahmen et al. Naturalistic path integration of Cataglyphis desert ants on an air-cushioned lightweight spherical treadmill. Journal of Experimental Biology (2017).