Artificial Meadows And Robot Spiders Reveal Secret Life Of Bees
Many animals learn to avoid being eaten by predators. Now ecologists have discovered that bumblebees can even learn to outwit colour-changing crab spiders.
Dr Tom Ings of Queen Mary, University of London will tell the British Ecological Society's Annual Meeting at Imperial College, London about how he and his colleague Professor Lars Chittka reached this conclusion using an artificial meadow containing robotic crab spiders.
The ongoing battle between predators and prey has fascinated ecologists for decades, and Ings is no exception. But instead of studying iconic predators such as lions or tigers, his interests lie closer to home with bumblebees and crab spiders.
According to Ings: “Crab spiders try to ambush unsuspecting flower visitors, such as bumblebees, by changing their body colour to match the flower they are lurking on. Even so, these spiders often fail to catch their prey, giving bees the chance to learn to avoid further - potentially fatal - encounters. We already know that animals, including bees, can learn to avoid predators, but we know almost nothing about how they do it. For example, do bees learn to avoid the location where they were attacked or the flower type on which they were attacked?”¯
To test how bumblebees learn to avoid predators such as crab spiders, Ings let them forage in a “meadow”¯ of artificial flowers and exposed the bees to a controlled predation threat from “robotic”¯ crab spiders. These robotic spiders, which consisted of a life-sized crab spider model and two remote-controlled, foam-coated pinchers, would capture and hold bees as they landed to feed. The meadow contained a mixture of yellow and white flowers with robotic spiders present on 25% of the yellow flowers in order to test whether bees' colour preference would switch from yellow to white after being attacked on yellow flowers.
“We found bees learnt to avoid flowers that look the same as those where they had previously been attacked. More importantly, after a few attacks bees started to avoid flowers of the same colour as those where they had previously been attacked, even if there were no spiders,”¯ Ings says.
As well as revealing fascinating insights into how bumblebees learn to avoid becoming a crab spider’s dinner, Ings’ results have important implications for pollination and raise interesting questions about evolution of predator camouflage.
“Many flowers rely on insects such as bees for pollination. So our finding that bees avoid flowers of the same colour as those where they were previously attacked could mean these flowers are less likely to be pollinated. Our results also raise interesting questions about evolution of predator camouflage. Spiders use up energy changing colour, which can take several days. So why do they waste energy camouflaging themselves if it does not increase their chances of capturing prey? It might be that camouflage reduces the chances of crab spiders being eaten by their own predators such as birds, but this idea still needs to be tested experimentally,”¯ says Ings.
Dr Ings will present his full findings on 3 September 2008 to the British Ecological Society’s Annual Meeting at Imperial College, London.