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Honeybees create mental maps to find their way home

A century of research has shown that honeybees are excellent navigators. They use a combination of cues and senses to find their way, including their sense of smell, the sun, patterns of polarized light, vertical landmarks and perhaps even the Earth’s magnetic field. And now, a new study published in the journal Frontiers in Behavioral Neuroscience has found that honeybees also use the layout of linear features in the environment to guide themselves home.

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

The researchers placed a beehive in each of five rural areas close to the village of Klein Lüben in Brandenburg, Germany. The five home areas, A–E, had a different number and layout of linear features, such as fields and roads, which the researchers referred to as “edges.” They also identified a test area where they planned to release bees, and which would represent a brand new, unexplored location with its own pattern of linear structures.

After the bees from each colony had acclimatized to their specific home areas, the researchers caught experienced foragers that had just fed at a feeding station. Each of the captured bees (a total of 50) was fitted with a tiny (10.5 mg) harmonic radar tracking device and transported to the test area to be released. All the bees were released at the same place in the test area, and their flight paths were then monitored for between 20 minutes and three hours as they familiarized themselves with the position of the hive in the new location. 

The presence and layout of linear features in the test area were not the same as in any of the home areas, A–E. These features most closely resembled the layout in Areas A and B, while being least similar to the layout in Area E. The researchers expected that honeybees released in the test areas would perform search flights interspersed with multiple returns to the release site, in order to familiarize themselves with the new layout. This is common behavior for honeybees that find themselves in a new and unfamiliar location. 

However, if the search flight patterns of individuals from the different home areas differed, then then researchers hypothesized that the memories of features from the home areas may affect the way in which the bees investigate and learn about their new area. 

The experts analyzed the flight patterns of released bees by quantifying the frequency with which each bee flew over of each 100 x 100 meter block within the test area. They then compared the results to random flight patterns generated by models. This revealed that the bees from the five home colonies did not use the same flight patterns to become familiar with the layout of the test area, and none of them simply flew around randomly during their orientation flights. 

Indeed, the analysis showed that the honeybees spent a disproportionate amount of time flying alongside the linear features in the test area. Analyses showed that these continued to guide the exploratory flights even when the bees were more than 30 meters away, the maximum distance from which honeybees are able to see such landscape elements. This implies that the bees kept them in their memory for prolonged periods.

Interestingly, the bees from home Area E, which was least similar to the test area and had few linear features, showed flight patterns that most closely resembled those predicted by the random flight models. The researchers suggested this indicated that these bees had not learned to use linear features to navigate in their home area. 

However, the bees from home Areas A and B, which were most similar to the test area and had numerous linear features, behaved differently from the modeled random flight patterns; the flights of these bees focused on the field, road and canal edges in the test area. This indicated to the researchers that the bees had acquired a navigation memory in their home area that made use of linear features, and they used this to help them learn about the layout in the test area.

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

The findings suggests that the bees retained a navigational memory of their home area, based on linear landscape elements, and were able to generalize this memory to help find their way back to the release site in the unfamiliar test area. This technique of finding one’s way home is reminiscent of what pilots did in the earliest days of human flight, before the invention of the first radio beacons, ground-based electronic systems or modern GPS. They commonly navigated by following roads and railways – striking linear landscape elements at ground level that guide towards a destination of interest.

“Flying animals identify such extended ground structures in a map-like aerial view, making them highly attractive as guiding structures. It is thus not surprising that both bats and birds use linear landmarks for navigation. Based on the data reported here we conclude that elongated ground structures are also salient components of the honeybees’ navigation memory,” concluded the authors.

By Alison Bosman, Staff Writer

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