Bumblebee defence is more than meets the eye
26 May 2010
A bumblebee's defence may also rely on its characteristic shape, flight pattern or buzzing sound, say scientists at Royal Holloway, University of London and Queen Mary, University of London.
Toxic or venomous animals, like bumblebees, are often brightly coloured to tell would-be predators to keep away. Remembering the colours the first time it gets stung may help a bird avoid trying to eat a bee again.
The researchers tested the idea that bumblebee species in the same location develop similar appearances to enhance protection from local predators.
The team compared the loss rates of bumblebees with different colour patterns in the same environment for populations in Sardinia, Germany and the UK. They expected that predators would be more likely to eat bees that looked different to those they had encountered previously in their local area.
The results were surprising.
"Predators didn't seem to target the unusually coloured bees from the non-native populations we tested. Perhaps the bumbling way in which all bumblebees fly, or their distinctive deep buzzing are more important clues to help would-be predators avoid a nasty sting," said Dr Nigel Raine, from Royal Holloway.
Birds differ from humans in the way they see the world, particularly their ability to see light in the ultraviolet range of the spectrum. Comparing the colour patterns of different bumblebee populations, the team found that the white tip of the bumblebee's tail reflects ultraviolet light strongly, making it particularly obvious to birds. Such signals are also important to bees, which detect ultraviolet markings on flowers that are invisible to us.
"Although birds can tell the difference between the colour patterns of the different bee populations in our experiments, they probably find it hard to tell them apart in the fraction of a second when a bee flies past. Perhaps it's better for the bird to steer clear of all animals which look, sound or fly like a bumblebee to avoid the danger of eating one," said Dr Raine.
The study was funded by the Biotechnology and Biological Sciences Research Council, the Engineering and Physical Sciences Research Council, the German Research Foundation and the Wellcome Trust.
Image: Bumblebee (Bombus terrestris audax) queen collecting pollen. Credit: Nigel Raine
Reference
Stelzer RJ et al. Effects of aposematic colouration on predation risk in bumblebees? A comparison between differently coloured populations, with consideration of the ultraviolet. J Zool 2010.
