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

Scientists have shown that honey bees remember the dominant linear landscape features in their home range, such as canals, roads, and borders. When transported to an unfamiliar area, they look for local elements of this kind, compare their arrangement with memory, and fly along them to find their way home. This navigation strategy is similar to that of 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 commonly navigated by following roads and rails—distinctive linear ground-level landscape features that lead 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 using their sense of smell, the sun, the sky pattern of polarized light, vertical landmarks that contrast with the panorama, and possibly the earth’s magnetic field. They are also smart learners, able to see connections between different memories in order to generalize rules.

Now scientists have shown that honey bees tend to find their way home by orienting themselves to the dominant linear landscape features, like the first pilots. The results are shown in Frontiers in behavioral neuroscience.

dr Randolf Menzel, Professor Emeritus at the Institute of Neurobiology at Freie Universität Berlin and first author of the study, explains: “Here we show that honey bees use a ‘navigational memory’, a kind of mental map of the area that they know to direct their foraging flights when They are looking for their hive in a new, unexplored area. Linear landscape features such as water channels, roads, and field edges appear to be important components of this navigational memory.”

Tiny transponder

In late summer 2010 and 2011, Menzel and colleagues trapped 50 experienced foragers near the village of Klein Lüben in Brandenburg and stuck a 10.5 mg transponder on their backs. They then released them into a new testing area that was too far away for the bees to be familiar with. A radar was located in the test area, which could detect the transponders at a distance of up to 900 meters. The most notable landmark in the test area was a pair of parallel irrigation channels running southwest to northeast.

When honey bees are in unfamiliar territory, they fly in reconnaissance loops in different directions and over different distances, centered on the release site. For between 20 minutes and three hours, the researchers used the radar to track the exact reconnaissance flight pattern of each bee. The bees flew up to nine meters above the ground during the experiment.

The researchers had collected foraging bees 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 features, particularly irrigation canals. The home area around hives D and E was very dissimilar in this respect, while the home area around hive C showed moderate similarity to the test area. Other landmarks that honey bees use for orientation, such as structured horizons or conspicuous vertical elements, were absent from the test area.

Non-random search pattern

Menzel et al. first simulated two sets of random flight patterns centered on the trigger point and generated with different algorithms. Since the observed flight patterns were very different from these, the researchers concluded that the honey bees were not simply conducting random foraging flights.

The researchers then used advanced statistics to analyze the orientation of the flights and their frequency of overflying each 100 x 100 meter block within the test area. They showed that the honey bees spent a disproportionate amount of time flying along the irrigation canals. Analyzes showed that these continued the reconnaissance flights even when the bees were more than 30 meters away, the maximum distance at which honey bees can see such landscape features. This implies that the bees kept them in their memory for a long time.

“Our data show that similarities and differences in the arrangement of linear landscape elements between their home range and the new range are used by the bees to explore where their hive might be located,” Menzel said.

navigational memory

Importantly, machine learning algorithms showed that the irrigation channels in the test area were the most informative for predicting reconnaissance flights of bees from hives A and B, less for bees from hive C, and least for bees from hives D and E. This suggests indicated that the bees retained a navigational memory of their home area based on linear landscape elements and attempted to generalize what they saw in the test area to its memory in order to find their way home.

“Flying animals identify such extensive ground structures in a map-like aerial view, making them very attractive as lead structures. It is therefore not surprising that both bats and birds use linear landmarks for navigation. Based on the data reported here, we conclude that these elongated ground structures are also prominent components of honeybee navigational memory,” the authors concluded.