September 21, 2012
Plight Of The Bumblebee: Using Trial And Error To Optimize Flight Route
April Flowers for redOrbit.com - Your Universe Online
Perhaps inspired by the amazing staccato sounds of Nikolai Rimsky-Korsakov's "Flight of the Bumblebee" (which if you haven't heard it, try the Wynton Marsalis trumpet interpretation), researchers at Queen Mary, University of London have been tracking bumblebees for the first time. They want to understand how the bees select optimal routes to collect nectar from multiple flowers before returning to their hive.
Working with the Harmonic Radar Group at Rothamsted Research, the research team used radar tracking to show how bumblebees discover flowers, learn their location and use trial and error to distinguish the most efficient route between them over large distances. The results of this study were published in the September 18 issue of PLOS Biology.
The team set up five artificial flowers in a 1-kilometer diameter field and fitted each flower with motion-triggered webcams. Each flower also had a landing platform with drops of sucrose in the middle.
"Using mathematical models, we dissected bees' learning process and identified how they may decipher this optimal solution without a map. Initially, their routes were long and complex, revisiting empty flowers several times," Dr. Mathieu Lihoreau explained. "But, as they gained experience, the bees gradually refined their routes through trial and error."
"Each time a bee tried a new route it increased its probability of re-using the new route if it was shorter than the shortest route it had tried before. Otherwise the new route was abandoned and another was tested. After an average of 26 times each bee went foraging, which meant they tried about 20 of the 120 possible routes, they were able to select the most efficient path to visit the flowers, without computing all the possibilities."
To ensure that the bees were focused on the artificial flowers, the experiment was conducted in October, when natural resources of nectar and pollen were scarce. To make sure that the bees visited all five flowers, the sucrose drops at each were only enough to fill one-fifth of the bee's crop. To prevent the bees from locating the nectar depots visually, the flowers were place in a pentagonal pattern at least 50 meters apart, which is approximately three times farther than a bee can see.
In previous research, the team showed that bees were capable of learning the shortest route possible to navigate between flowers in the lab, but this is the first time they have been able to observe this behavior in natural settings. This is also the first time they have been able to describe how the bees may be optimizing their routes.
"The speed at which they learn through trial and error is quite extraordinary for bumblebees as this complex behavior was thought to be one which only larger-brained animals were capable of," said Professor Lars Chittka.
"Interestingly, we also found that if we removed a flower, bees continued looking at that location — even if it was empty for an extended period of time. It seems bees don't easily forget a fruitful flower."
The motion-triggered webcams were used with tiny bumblebee-mounted radar transponders to track the bees. What the recordings showed was that bees exhibit highly individualistic behaviors — each bee had a favored arrival and departure direction, different from the other bees.
Professor Chris Rawlings, head of Computational and Systems Biology at Rothamsted Research, said, "This is an exciting result because it shows that seemingly complex behaviors can be described by relatively simple rules which can be described mathematically.
"This means we can now use mathematics to inform us when bee behavior might be affected by their environment and to assess, for example, the impact of changes in the landscape."