Familiar view

This honey bee will soon be released at a distance of three kilometers from its hive. The chip on its back provides the researchers with information on how long it takes the bee to return home. (Photo: Mario Pahl)

What happens when bees are displaced to unfamiliar locations? Quite a few of them find their way back to the hive even from great distances – provided that a certain condition is satisfied. The relevant details are reported by researchers from Würzburg and Canberra in a new publication.

The proverbial diligence of the honeybee is a fact: These industrious foragers are continuously on the lookout for pollen, nectar and water, often covering great distances in the process. In order to avoid getting lost, the animals orient themselves by means of several features, such as the position of the sun, the plane of vibration of polarized light, certain landmarks in the landscape and any distances already traveled. They can also relay this information to their hive mates by means of the so-called waggle dance.

Bee researchers from the University of Würzburg and from the Australian National University in Canberra have now examined whether bees are able to find their way back to the hive even if displaced to unfamiliar locations. Their study is published in the journal Plos ONE.

"In our experiments, we found that – from distances above three kilometers – the successfully returning bees mainly came from a specific geographic direction," says Mario Pahl. Pahl is a doctoral student in the Beegroup, a team of bee researchers at the University of Würzburg. Released in the right direction, the bees made it back to their hive even if they had to travel distances greater than eleven kilometers.

"We assume that bees are able to recognize the panorama of the landscape and take it into account in determining their position," says Pahl. If the panorama seems familiar to the honey-collector, it knows which direction to take for the homeward flight even from a great distance. Without the familiar view, in contrast, the bees have a hard time deciding where to go.

The experiment

In the study, the scientists caught foraging bees as soon as these reached their hives and placed them in a black box. Then, they transported the boxes to selected spots that were located to the north, east, south and west of the hive and released the bees at distances varying between several hundred meters and 13 kilometers. At some points, mountains blocked the view in the direction of the hive, thus complicating the task of finding home.

"On their foraging trips, the bees continuously store distance and directional information in order to be able at any time to fly back to their hive in a straight line. By catching them at the entrance to the hive directly after their return, we set the navigation system of the bees back to zero. After their displacement, they lacked any directional or distance information in relation to their hive. In this way, we ensured that they had to rely on already acquired knowledge about the landscape," says Pahl.

In order to determine whether the displaced animals managed to return to the hive and how long it took them to do so, the researches used some sophisticated technology: "Each bee was provided with a tiny chip on the chest, containing an individual ID," says Pahl. A receiver placed at the entrance of the hive then recorded the exact arrival time of each individual animal – including bees that did not return to their hive until several days later.

The result

"Bees coming from the eastern direction reached the hive significantly faster than bees that were released in the north, west and south," says Pahl, summing up the results of the experiments. Furthermore: "When we released the bees at distances greater than seven kilometers, only those from the east successfully found their way home."

According to the scientists, the reason for this is the formation of the landscape: the animals starting their homeward flight from the east, viewed a certain landmark, the so-called Black Mountain, from a familiar perspective. Unlike their competitors, they were thus provided with an important clue as to the direction in which to look for the hive.

Another fascinating fact that caught the attention of the scientists: It took some bees two to three days of traveling until their return was recorded by the receiver at the entrance to the hive. This is an indication of their ability to retain information on their route and on the landscape for long periods of time."It is fascinating to see that the honey bee can keep so much information with a brain only the size of a small seed," says Pahl.

The research was conducted in a collaborative project between the bee study group of the Vision Centre at the Research School of Biology, Australian National University, lead by Professor ShaoWu Zhang, and the Beegroup at the University of Würzburg, led by Professor Jürgen Tautz.

“Large Scale Homing in Honeybees”, Mario Pahl, Hong Zhu, Jürgen Tautz, Shaowu Zhang, Plos One, doi:10.1371/journal.pone.0019669.t001

Contact person

Mario Pahl, Department of Zoology II, T: (0931) 31-89176, E-mail: mario.pahl@uni-wuerzburg.de

By: Gunnar Bartsch

18.05.2011, 15:00 Uhr