Pollinators don’t just wing it when it comes to finding a sweet treat: the shape, colour, perfume and even electrical charge of flowers are all known to offer clues.
But now researchers say bumblebees also use another floral feature to guide them: how the concentration of a scent varies across the flower’s surface.
“[This study shows that] bees can tell the difference between flowers where the only difference is their spatial arrangement of scent – and that suggests they could use that information to make their foraging more efficient,” said Dr David Lawson, co-author of the research from the University of Bristol.
What’s more, scientists found that bees appear able to apply what they have learnt from patterns of scent to patterns of colour, suggesting the fuzzy critters might be even smarter than suspected.
Writing in the journal Proceedings of the Royal Society B, Lawson and colleagues from the University of Bristol and Queen Mary University of London reveal how they exposed 31 bumblebees, one at a time, to plastic discs in which an array of tiny wells were filled with peppermint oil to create either a cross or a square pattern .
One group of bees encountered a sugar solution placed in the centre of the discs with a circular pattern of peppermint oil, the other group found the sweet reward on discs with a cross-shaped pattern. Meanwhile water was placed on the “flowers” with the alternative pattern to those bearing the treat.
Once the bees drank from the sugar-bearing “flowers” on more than eight out of 10 consecutive occasions the team deemed them trained and let them lose, one at a time, on another set of 10 flowers. Half of these had a peppermint cross pattern, and half had a circular pattern, with water placed in the centre of all of them.
The team found that bees trained to head for flowers with a circular scent pattern preferentially spent time drinking on such flowers, even though there was no sugary treat, while those trained to go to the cross pattern, preferred to drink from flowers with a peppermint cross.
That, said Lawson, reveals bumblebees can tell blooms apart simply by the way a scent is distributed across a flower.
The team then presented a group of trained bees with two sorts of unscented paper discs bearing a sugary drink, one with red dots arrange in a cross, the other with the dots arranged in a circle, and watched where the bees went on their first 10 landings.
The results show that bees trained to bumble off to a peppermint-scented cross were more likely to choose to visit the cross-shaped array of red dots.
“There could be some kind of sensory overlap between vision and olfaction, ” said Lawson. “It is kind of like a human looking in a handbag and making a visual interpretation of what they are feeling with their hands.”
The team went on to present untrained bees with “flowers” boasting both a scent pattern and coloured visual pattern, finding that bees learned which blooms hosted a sweet treat faster when the patterns matched than when they were at odds. However the effect was only pronounced for circular scent patterns.
Dr Paul Graham, an expert in insect navigation from the University of Sussex, said the discovery that bees trained on a cross scent are able to recognise the same pattern visually was fascinating, although he said it wasn’t necessarily the case that bees are demonstrating an abstract sense of shape.
“That is something we think of as being an ability of clever animals,” he said. “Of course the thing now is we have to work out how a bee does that.”
THE GUARDIAN - NICOLA DAVIS
