Veteran bumblebees more protective, don't mentor newbies, study finds

Bumblebees that are more experienced in foraging do not appear interested in sharing their wisdom with bees just learning their way around, a new study involving a University of Guelph researcher has found.

In a controlled test involving fake flowers, researchers also found that newbies wanted to follow the experienced bees, rather than strike out on their own to explore the flower patch and potentially find an untapped pollen source.

"They seem to attract towards each other," Nigel Raine, the Rebanks Family Chair in Pollinator Conservation at the university, told CBC News.

When confronted with a newcomer bee, the experienced bees that knew their way around the pollen patch became protective of the flowers that they previously visited, despite the availability of untapped flowers.

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"They were engaging in more competitive interaction on flowers than we expected them to, because there were enough flowers in our flight cage that they could have just picked separate groups of flowers and completely avoided that competition."

It was the first time researchers have looked at foraging routes followed by multiple bees at the same time.

Flight cage and artificial flowers

Raine completed the study with Mathieu Lihoreau, currently at the University of Toulouse in France, and Lars Chittka from Queen Mary University of London.

The researchers set up a 20 by 40 metre flight cage – one of the largest ever used in bee research – that had artificial flowers fitted with motion-sensitive video cameras and controlled nectar flow rates.

The bees were tagged with numbers so researchers could identify them as they landed on the artificial flowers. Over a three week period, the researchers released pairs of bees into the cage. The first bee was allowed to forage 25 times before a second, less-experienced bee was released.

When the less-experienced bee tried to land on the same flower with a bee that had already been foraging, the more experienced bee showed aggression and would try to kick the newcomer bee out of the flower.

The "pushing and eviction behaviour" started to happen after the more experienced bee would land on a flower that was part of its route and discovered it had already been emptied by the less experienced bee, Raine said.

If the less-experienced bee managed to evict the experienced bee, the newbie was more likely to revisit that flower on future foraging trips. In fact, both bees increased how often they visited that flower.

The researchers also found that the efficiency of the more experienced bees dropped when the less experienced bees were introduced to the flight cage. 

Foraging habits important for crops

Raine said bees are simple creatures, but they must complete the complex task of getting to the most number of flowers in the shortest trip. Figuring out the optimal route takes time and experience. 

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"The novelty factors are that we're looking at the interactions between the bees, and that's not something that's been done before, and that we found these differences in how it affected the foraging of both individuals," Raine said.

"Understanding how bees move in the landscape and how they forage is obviously really important for agricultural production generally because these are important crop pollinators."

The study was completed in August 2010 at the Centre for Agricultural Bioscience International centre in Egham, England. 

The study was published March 16 in the journal PLoS One.