May 19, 2011

Bees ‘Read Sky’ To Find Home

Bees can find their way home from an amazing 11 kilometers away over several days' travel, thanks to their ability to remember landmarks and read information from the sky, a new study shows.

Vision scientists have found more reasons for the honeybee's incredible knack of navigating cross-country"“ these creatures often rely on the position of the sun, the polarization of light in the sky, the panorama view of the horizon and landmarks including towers, mountains or lakes.

Led by Professor ShaoWu Zhang from The ARC Centre of Excellence in Vision Science and The Australian National University (ANU), the research team released bees in Canberra, where the landmarks include Black Mountain, Mount Ainslie, Red Hill and Lake Burley Griffin.

"We found that from four kilometers onwards, honeybees homing from the eastern direction return to their hives sooner than bees from the north, west and south," says Prof. Zhang. "Also, when we released these bees from seven kilometers and above, only those from the east can successfully find their way back.

"This is because bees released from the east can see Black Mountain in the opposite direction. It also helps if they are released in the early afternoon, when the sun is situated in the west, too. When they fly towards Black Mountain, familiar local features can guide them back to the hive."

In the study, the team caught foragers as they returned to their hives and displaced them in a black box. The bees were then released in novel spots at various distances up to 13 kilometers in north, east, south and west.

"In their forage trips, one way that honeybees use to find their way home is by storing distance and directional information when they venture out," Prof. Zhang says. "In other words, they try to go back the way they came.

"Catching them as soon as they reach their hives and placing them in a black box sets their pre-calculated information back to zero, so the bees are deprived of any directional information in relation to the hive. By doing this, we can confirm that they are relying solely on knowledge that they have gathered about the landscape to travel home."

The team also used new technology to track the bee's journey. They placed Radio Frequency Identification (RFID) tags on each bee and left a receiver at the hive entrance. The system recorded the exact arrival time of the individually targeted bees, including the late arrivals, ensuring accurate results without having a researcher keep watch for hours on end.

"Bees released from longer distances did not reach their hives until two to three days later," he says. "What took us by surprise was the bee's ability to retain their knowledge of the landscape and directions for several days.

"It's fascinating that the honeybee has a brain the size of a small seed, but it still can keep so much information, and has so many creative ways to survive."

The research was carried out in collaboration with the "ËœBEE group' at Wrzburg University, Germany, led by Professor Jrgen Tautz. Professor Zhang also thanked The Vision Centre and The Australian National University for their support of this research.

The study "Large Scale Homing in Honeybees" by Mario Pahl, Hong Zhu, Jrgen Tautz and ShaoWu Zhang was published last week in PloS ONE. It is available at http://bit.ly/in4XIr.

The Vision Centre is funded by the Australian Research Council as the ARC Centre of Excellence in Vision Science.


Image Caption: This honeybee pollen forager is being released 3km from her hive. The RFID chip on her back enables researchers to measure the bees' exact flight times and homing success. Photo by Mario Pahl (ANU)


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