Signals from mobile phones could be partly to blame for the mysterious deaths of honeybees, new research shows.



In the first experiment of its kind, a bee expert placed a mobile phone underneath a hive and then carefully monitored the reaction of the workers.



The bees were able to tell when the handsets were making and receiving calls, and responded by making the high pitched squeaks that usually signal the start of swarming.

Impact: Researchers found bees responded when mobile phones were used to make and receive calls

Dr Daniel Favre, who carried out the experiment, believes signals from mobile phones and masts could be contributing to the decline of honeybees and called for more research.



But British bee experts say there is still no evidence that mobile phones posed a risk.



They blame the vanishing honeybees on changes in farming, the decline of wild flowers and pesticides.



The number of honeybees in the UK has halved in the last 25 years while in America bees have been badly hit by 'colony collapse disorder' - the sudden disappearance of entire colonies over winter.



Experts say bees have been badly hit by the varroa mite, a blood-sucking parasite that makes colonies vulnerable to disease, freak weather or poisoning.

Some experts say the latest generation of pesticides may disrupt the nervous systems of bees, causing them to get lost and confused.



And most bee experts say the creatures are suffering from the loss of wild flowers, meadows, rough pasture and untidy gardens.



However, a handful of experts say mobile phones could also be partly to blame.

Dr Favre, a teacher who previously worked as a biologist at the Swiss Federal Institute of Technology in Lausanne, said: 'This study shows that the presence of an active mobile phone disturbs bees - and has a dramatic effect.'



He placed two mobile phones under a beehive and recorded the high pitched calls made by the bees when the handsets were switched off, placed on stand-by and activated.



Around 20 to 40 minutes after the phones were activated, the bees began to emit "piping" calls - a series of high pitched squeaks that announce the start of swarming.



Within two minutes of the phone call ending, the worker bees calmed down.

In the study, the bees did not swarm - even after 20 hours' exposure to mobile phone signals. However, the onset of unexpected swarming triggered by mobile phone signals could have 'dramatic consequences in terms of colony losses', Dr Favre reports in the bee keeping journal Apidologie.



The study did not show that mobile phones were deadly for bees, he said.



"But one hypothesis is that electromagnetic fields could be contributing to the disappearance of bee colonies around the world," he added.



But British bee expert Norman Carreck of Sussex University said: 'It's an interesting study but it doesn't prove that mobile phones are responsible for colony collapse disorder. If you physically knock a hive, or open one up to examine it, it has the same result.



'And in America many cases of colony collapse disorder have taken place in remote areas far from any mobile phone signals.'