The robotic system offers a hidden window into the collective behavior of bees

By Celia Lutherbacher

Honey bees are notoriously finicky when it comes to studying. Instruments and research conditions and even unfamiliar odors can interfere with colony behavior. Now, a joint research team of Mobile Robot Systems Group in the EPFL School of Engineering and School of Computer Science and Communications and Hiveopolis a project at Austria’s University of Graz has developed a robotic system that can be built discreetly into the framework of a standard honey bee hive.

Consisting of an array of thermal sensors and actuators, the system measures and modulates honey bee behavior through local temperature variations.

“Many of the rules of bee society – from collective and individual interactions to rearing healthy broods – are regulated by temperature, so we utilized them for this study,” explains EPFL PhD student Rafael Barmak, first author of a paper on the system recently published in Science Robotics. “Thermal sensors create snapshots of the bees’ collective behavior, while actuators allow us to influence their movement by modulating a thermal field.”

“Previous studies of the thermal behavior of honey bees in winter relied on either observing the bees or manipulating the outside temperature,” adds Martin Stefanec of the University of Graz. “Our robotic system allows us to change the temperature from within the cluster, mimicking the heating behavior of core bees there, and allowing us to study how the winter cluster actively regulates its temperature.”

‘Biohybrid superorganism’ to reduce colony collapse

Bee colonies are difficult to study in winter because they are sensitive to cold, and opening the hive risks harming them as well as affecting their behavior. But thanks to the researchers’ biocompatible robotic system, they were able to study three experimental nests, located in the Artificial Life Laboratory at the University of Graz, during the winter and control them remotely from the EPFL. Inside the device, a central processor coordinates sensors, sends commands to actuators, and transmits data to scientists, indicating that the system can be used to study bees without distraction – or even a camera – needed.

The head of the Mobile Robot Systems Group Francesco Mondada explains that one of the most important aspects of the system – which he calls a ‘biohybrid superorganism’ because of the combination of robotics with individual colonies acting as living entities – is its ability to simultaneously observe and influence the behavior of bees.

“By collecting data on the position of the bees and creating a warmer area in the hive, we can encourage them to move in ways they would normally not be able to do in nature during the winter, when they tend to swarm to conserve energy. This gives us the possibility to act on behalf of the colony, for example by directing it to a food source, or preventing it from dividing into groups that are too small, which could threaten its survival.”

The robotic system is shown in a test nest © MOBOTS / EPFL / Hiveopolis

Scientists were able to extend a colony’s survival after the death of its queen by distributing heat energy through actuators. The system’s ability to reduce colony collapse could have implications for the survival of bees, which has become a growing environmental and food safety issue as global populations of pollinators have declined.

Behavior never seen before

In addition to its potential to support colonies, the system has explained previously unobserved honey bee behavior, opening new avenues of biological research.

“Local thermal excitations generated by our system reveal previously unreported dynamics that generate exciting new questions and hypotheses,” said EPFL postdoctoral researcher and associated author Rob Mills. “For example, currently, there are no models that can explain why we can encourage bees to traverse the cold ‘valleys’ of the hive.”

The researchers now plan to use the system to study bees in summer, which is a critical period for raising young. In parallel, the Mobile Robotic Systems Group is exploring systems that use vibrational pathways to interact with honeybees.

“The biological acceptability aspect of this work is very important: the fact that bees accept electronic integration into the hive gives our device great potential for different scientific or agricultural applications,” says Mondada.

This work was supported by the EU H2020 FET HIVEOPOLIS project (no. 824069), coordinated by Thomas Schmickl, and by the Field of Excellence COLIBRI (Complexity of Life in Basic Research and Innovation) at the University of Graz.