Bees follow linear landmarks to find their way home, just like the first pilots

Scientists have shown that honey bees retain the memory of the dominant linear landscape features in their native area such as paths, roads and borders. When transported to an unfamiliar area, they look for local features of this type, compare their layout with memory, and fly with them to find their way home. This navigation strategy is similar to that followed by the first human pilots.

In the earliest days of human flight, before the invention of the first radio beacons and ground-based electronic systems, and modern GPS, pilots usually navigated by following roads and railways – hitting linear landscape features at ground level which leads to a destination of interest. .

Enter the honey bee. A century of research has shown that honey bees are navigators par excellence. They can navigate by their smell, the sun, the pattern of polarized light in the sky, vertical landmarks that stand out from the panorama, and possibly the Earth’s magnetic field. They are also intelligent learners, able to identify connections between different memories to generalize rules.

Now, scientists have shown that honeybees tend to search for their way home by orienting themselves to the dominant linear landscape features, just like the first pilots. The results are shown in Frontiers in Behavioral Neuroscience.

Dr. Randolf Menzel, professor emeritus in the Department of Neurobiology of the Free University of Berlin, and lead author of the study, explained, “Here we show that honeybees use a ‘navigational memory’, a kind of mental map of that area. They know, their guide search flights as they search for their hive starting in a new, unexplored area. Linear landscape features, such as waterways, roads, and field edges, appear to be important components of this navigational memory.”

A tiny transponder

In the late summer of 2010 and 2011 near the village of Klein Lüben in Brandenburg, Menzel and colleagues captured 50 experienced honey bees and stuck a 10.5-mg transponder on their backs. They then released them in a new test area, which was too far away for the bees to know. In the test area there was a radar, which could detect the transponders at a distance of up to 900 meters. The most prominent feature in the test area was a pair of parallel irrigation channels, which ran south-west to north-east.

When honeybees find themselves in an unfamiliar territory, they fly in exploratory loops in different directions and over different distances, focused on the release site. With the radar, the researchers tracked each bee’s precise exploratory flight pattern for between 20 minutes and three hours. The bees flew up to nine meters above the ground during the experiment.

The researchers collected foragers from five hives: the home area around hives A and B was similar to the test area in terms of the number, width, length and angle of linear landscape elements, especially irrigation channels. The home range around hives D and E was very dissimilar in this respect, while the home range around hive C was intermediate in line with the test area. The test area did not contain other landmarks that honey bees are known to navigate, such as a structured horizon or protruding vertical elements.

Non-random search pattern

Menzel et al. first simulated two sets of random flight patterns, centered on the release location, and generated with different algorithms. Since the flight patterns observed were very different from these, the researchers concluded that the honey bees were not just making random search flights.

The researchers then used advanced statistics to analyze the orientation of the flights and their flight frequency over each 100 x 100 meter block within the test area. They showed that the honey bees spent a disproportionate amount of time flying alongside the irrigation channels. Analysis showed that these continued to guide the exploratory flights even when the bees were more than 30 meters away, the maximum distance from which honey bees can see such landscape features. This suggests that the bees kept them in their memory for long periods.

“Our data show that the bees use similarities and differences in the layout of linear landscape elements between their home area and the new area to explore where their hive might be,” said Menzel.

Navigation memory

Importantly, machine learning algorithms showed that the irrigation channels in the test area were the most informative in predicting the exploratory flights of bees from hives A and B, less so for bees from hive C, and for bees from hives D and E. that the bees retained a navigational memory of their home area, based on linear landscape features, and tried to generalize what they saw in the test area to memory to find their way home.

“Flying animals recognize such extended ground structures in a map-like aerial view, making them particularly attractive as directional structures. It is therefore not surprising that both bats and birds use linear landmarks for navigation. Based on the data reported here it is concluded that long-distance structures are also significant components of honey bee navigational memory,” the authors said.