May 30, 2010

Bee Stripes May Not Deter Predators

Scientists say that bumblebees' distinctive bright yellow and black stripes may not be what is keeping them safe from their enemies.

A U.K. study has discovered that other aspects of bees' behavior may matter more than the classic bee color to keep predators away.

The scientists told BBC News that a bee predator's true deterrent could be the way the bumblebees fly or perhaps the buzzing sound they make.

The study was published in the Journal of Zoology.

Scientists have long believed that once flying predators get stung by a bee they remember their experience and rely on color to identify their prey in the future.

"The first time a bird eats a brightly colored bumblebee it gets a nasty surprise. Remembering the bee's bright colors may help the bird to avoid making the same mistake again," Dr Nigel Raine from the School of Biological Sciences at Royal Holloway, University of London, a researcher on the study, told BBC News.

Birds perceive the world differently than humans by having the ability to see light in the ultraviolet range of the spectrum. However, the scientists said they can still distinguish between different species of bees.

The researchers wanted to check if bees' colors were the only thing that helped to ward off predators.

Raine and his colleagues from the University of London set up a group of colonies from different populations of bumblebees in the U.K., Germany and Sardinia.

Even though some insects had similar color patterns, others looked quite different from one another.

"In the UK, they are yellow-and-black-striped with a white tip on the abdomen, but in the Canary Islands for example they don't have any yellow bands at all - they're just black and white," Raine told BBC.

The scientists expected birds to rely on visual cues, which means they would be more likely to attack bees if they looked different from the ones they were used to.

"All our bees were individually numbered with tags on the back of the thorax, so that we could keep track of each individual that left and entered the nest," the researcher told BBC.

The researchers counted how many bees did not return to their nest and compared that loss rate to different Bombus terrestris populations with different color patterns within the same environment.

Rain said that brought some unexpected results.

"Predators didn't seem to target the unusually colored bees more than the 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," he said.

The researchers called the findings surprising.

"The results mean that the explanation for the bumblebees' coloration patterns is not as simple as previously thought," Ralph Stelzer, the main author in the study, told BBC.

The scientists theorize that perhaps birds prefer not to take any chances and just steer clear of all insects that look, sound or fly like bees.


On the Net:

Journal of Zoology

School of Biological Sciences at Royal Holloway, University of London