Bees capable of solving complex mathematical problem

29 October 2010

Bumblebees often have to forage for food in patches of flowers several kilometres apart. In calculating the best route, bees are able to rapidly solve a complex mathematical problem.

Scientists from Royal Holloway, University of London and Queen Mary, University of London have been studying the movement of bees between groups of flowers. It is known that bees travel between plants in a pre-planned order - known as 'traplining'. The researchers have shown that bumblebees (Bombus terrestris) learn the shortest routes between the patches, and effectively solve the 'travelling salesman problem'.

This mathematical problem involves a salesman who has to visit a number of locations, each only once. Calculating the shortest route between the locations requires high levels of computing power, with the complexity increasing exponentially with the rising number of locations. However, bees are able to solve this problem using brains the size of a grass seed.

The team used computer-controlled artificial flowers to test whether the route the bees followed was a result of the order in which they found the flowers, or a more efficient route.

After initial exploration the majority of bees quickly learned the optimal foraging route, with 80 per cent travelling the shortest distance between the flowers. Although traplining has been reported in a number of animals - specifically birds and insects - the question of how they distinguish the shortest path is not yet understood.

"Foraging bees solve travelling salesman problems every day. Because bees use a lot of energy to fly, they find a route which keeps flying to a minimum," says Dr Nigel Raine from Royal Holloway, who led the research.

"Despite their tiny brains, bees are capable of extraordinary feats of behaviour. We need to understand how they can solve the travelling salesman problem without a computer. What short-cuts do they use?" he adds.

It is hoped that enhancing our knowledge of how bees navigate landscapes will allow scientists to explore new solutions to the travelling salesman problem, which has many applications in modern life, such as in the design of traffic networks and business supply chains.

This work was funded by the Wellcome Trust, the Biotechnology and Biological Sciences Research Council, and the Engineering and Physical Sciences Research Council.

Image: Head of a honey bee. Credit: Annie Cavanagh, Wellcome Images

Reference

Lihoreau M et al. Travel optimization by foraging bumblebees through readjustments of traplines after discovery of new feeding locations. Am Nat 2010.