Bees can solve the Traveling Salesperson Problem

Who wouldn’t hurry to visit this delicious flower?
Who wouldn’t hurry to visit this delicious flower?
Image: Reuters/Stephanie Made
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Technology has made navigation easy for humans, with electronic maps that instruct us aloud so we needn’t learn directions at all. Bees, obviously, don’t have that option, and they also have very small brains—yet their navigation skills rival those of even the most adept human travelers.

According to a study published in Scientific Reports on Dec. 11, the flight of the bumblebee even becomes more efficient over time. A research team, led by Joseph Woodgate of the biological and experimental psychology department at Queen Mary University of London, used a harmonic radar tracking system to study bee navigation, following the insects’ flight paths within a set of artificial flowers. They discovered that bees are in a continual process of optimizing their routes over time.

Until now, scientists have studied bees’ movement by looking at the length of their flights, as well as where they land. No prior study created a brand new environment to follow bees continuously as they navigate it. The researchers say that new tracking technology enabled them to track the insects while they were learning new paths, collecting location data every three seconds. Their experiment suggests that the small-brained bugs are capable of solving complex routing issues, skillfully contending with what’s known as “the traveling salesperson problem.”

Traveling salespeople learn the fastest route from Point A to Point B to Point C. The most efficient paths are not always most direct, nor are they necessarily the same coming and going from a single location. The challenge is to find a route that visits each destination while traveling the shortest possible distance. The study’s coordinator, zoologist Lars Chittka explained this conundrum in a statement:

Imagine a sales[person] from London who needs to call at Manchester, Leeds, Glasgow, Edinburgh, and Inverness before returning home. From Manchester, it is tempting to make the short trip across to Leeds, and from Glasgow it is tempting to visit Edinburgh, but a sales[person] who does that will soon find themselves stranded in Inverness with a very long drive home. The better solution is to travel up one side of the UK and return down the other.

Past research that looked only at the order in which small foragers like birds and bees arrive at each destination, showed that they often find optimal solutions—but it couldn’t explain how the animals decreased flight times. To figure that out, the bee research team set up five artificial flowers, which were not as attractive as real flowers but did offer the bees sweet nectar when they landed. Scientists then tracked the insects over two days as they explored the paths and developed routes.

A bee drawn to an artificial flower keeps figuring out how to get here faster.
A bee drawn to an artificial flower keeps figuring out how to get here faster.
Image: Joseph Woodgate

Like people, bees are creatures of habit. The study’s bees established favorite paths early on and followed them regularly, limiting exploration with time. They also became better navigators with each flight, changing route sequences to improve speed from one feeder to another until they found the best paths, and becoming increasingly adept at their favorite flights. They never became completely set in their ways, however.

The research team believes their work can inform a few very different fields of study. For one, it improves understanding of how bees and other pollinating insects search for food and operate, which can help humans minimize risks posed by habitat loss and increased agriculture. The study also adds to a growing body of knowledge on animal cognition, used to understand both animal and human brains. Lastly, the researchers say, their findings could come in handy for technologists developing machines that navigate. In the future, when your GPS tells you to turn left, you may have a bee to thank for the information.