Bumblebees Mark Their Trails With Tiny Scented "Footprints"

Yani Dubin via Flickr Creative Commons // CC BY-ND 2.0
Yani Dubin via Flickr Creative Commons // CC BY-ND 2.0 / Yani Dubin via Flickr Creative Commons // CC BY-ND 2.0

Bees seem to have an endless number of tricks up their sleeve—and on their feet. Scientists have discovered that bumblebees leave itty-bitty scented “footprints” on every flower they visit, thereby informing other foragers that the bloom’s been recently tapped. The researchers published their findings in the journal Nature Scientific Reports.

Bees are the queens of complex communication. They exchange information with one another and their environments using a dazzling array of sensory input, including electrical impulses, sound, dance, and chemical signals.

Some of those signals flow out into the world through the bees’ delicate little feet. The bottom segment of a bee’s leg, called the tarsus, secretes a scented goo that helps the bee stick to the soft surfaces of flower petals. The chemical profile of each bee’s foot-glue is as unique as a fingerprint.

Previous studies have shown that bees glean important information from one another’s goo, skipping flowers that other bees have already visited. This raised an interesting question: If a bee can "read" another bee’s scent mark, can it also identify that bee?

To find out, researchers planted small clusters of fake flowers in the laboratory and topped some of them up them with sucrose nectar. They then gave bumblebees (Bombus terrestris) free rein to tromp around the blossoms, marking them up and taking in the marks of other bees that had come before.

The bees proved careful and canny readers. Not only did they use other bees’ scent marks to decide which flowers to probe, but they also considered the source of the scent when making that decision. An individual bee could easily differentiate between the smell of its own feet (trustworthy), those of its family members (very trustworthy), and those of strangers (not a reliable source of floral information).

Lead author Richard Pearce is a biologist at the University of Bristol. "Bumblebees are flexible learners and, as we have discovered, can detect whether or not it is they or a different bumblebee that has visited a flower recently. These impressive abilities allows them to be cleverer in their search for food, which will help them to be more successful," he said in a statement.