How bees use features in the landscape to navigate home
For an insect with a brain the size of a seed, the honeybee has a most impressive list of skills. Its amazing navigational abilities, such as scoring perfect landings, or performing complex flight manoeuvres, have helped the advancement of flight technology, including unmanned aircraft vehicles (UAV).
Vision scientists have recently uncovered another ability of the honeybee – it can find its way home from an astounding 11 kilometres away over several days’ travel by remembering global landmarks and reading information from the sky.
Previous research has shown that honeybees return home by remembering landmarks around the hive, the panorama view of the horizon, using the sun and polarised skylight as compasses and by memorising their outbound flight paths.
The study, led by Professor ShaoWu Zhang from The Vision Centre and The Australian National University, was aimed to find out if these creatures could remember the way home from new locations that are far away. The bee hive used in the research was located at the centre of three global landmarks in Canberra – Black Mountain, Mount Ainslie and Lake Burley Griffin.
Starting in the mornings, the research team captured pollen-carrying foraging bees as they returned to the hive. These bees were displaced in a black box and brought to locations of four cardinal directions – north, east, south and west.
“Capturing the bees when they’ve just returned, ensures that the creatures are relying solely on their knowledge of the surrounding landscape to go home.” Professor Zhang explains.
“In their forage trips, one way that honeybees use to find their way back is by storing distance and directional information when they venture out,” he says. “In other words, they try to go back the way they came.”
“Catching them as soon as they reach their hives sets their pre-calculated information back to zero. As they are placed in a black box until we reach the releasing spots, these bees are ‘blindfolded’, and do not have any directional information in relation to the hive. “
Anticipating that the bees will return at different times, the team used new technology to track their journey. Before the bees were whisked off to various locations, they were immobilised on ice and had Radio Frequency Identification (RFID) tags placed on their thorax. The researchers then placed an RFID receiver at the entrance of the hive, allowing the system to record the exact arrival time of each bee, including the late arrivals. This ensured accurate results without having a researcher keep watch for hours on end.
The results show that bees released from 1500 meters radius away had no trouble finding home, due to familiar local features surrounding the hive.
“1500 meters radius was considered a close location, so it was expected that the bees would find their way home easily” Professor Zhang says. “At 4000 meters – the medium scale – bees coming from the east were the quickest in finding their way back, compared to those flying from other directions.”
“At a distance from 7000m onwards, only bees from the east successfully returned home.”
Professor Zhang explains that the homing ability of these honeybees was not related to the cardinal directions, but to where the landmarks were situated.
“Bees that were released in the east could see Black Mountain in the opposite direction. As they start their journey in the early afternoon, the sun in the west leads them to the specific landmark. Once they fly towards Black Mountain, familiar local features would guide the bees back to the hive.”
“When we set up a panoramic view of the surrounding area as seen from the hive, we could see distinctive shapes of Black Mountain in the west and Mount Ainslie in the east. Black Mountain was thus a landmark beacon for the creatures,” he says.
The researchers also found that bees released from longer distances did not reach their hives until two to three days later. This is because the bees had to constantly drink nectar to refuel, or spend time searching for the correct paths.
What took the team by surprise, Professor Zhang says, 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.”
Professor Zhang is now conducting a similar research about the homing abilities of honeybees in China.
The research was carried out in collaboration with the ‘BEE group’ at Würzburg University, Germany, led by Professor Jürgen Tautz. Professor Zhang also thanked The Vision Centre and The Australian National University for their support of this research.
by Mandy Thoo