New research carried out at the Swiss Federal Institute of Technology has found that bees buzz differently near mobile phone signals – causing behaviour that endangers colonies.

The research has shed light on another modern threat to bee colonies, which are already being killed off at a massive rate by pesticides and parasites.

Researchers placed two mobile phones in beehives and operated them alternately in standby mode and in connection to each other.

Results showed that when the phones were on standby, the bees' buzzing did not change, but when the phones were activated, the bees' buzz frequency rose significantly.

"This is clear evidence that the bees are sensitive to phone signals and are disturbed by mobile phones," said research director Daniel Favre.

Favre explained that bees normally only hum at a high frequency when they are about swarm out of a hive in search of food. He said that mobile phones could therefore cause the bees to leave the hive prematurely, before the queen has fully matured and there are no larvae to feed.

The disappearance of bees would have a devastating effect on the environment, as many trees and plants rely on them to reproduce.

The first major indication that bees were increasingly under threat came in 2006, when there was a wave of bee deaths in the US. Some beekeepers reported losing 90 percent of their populations, and the term "colony collapse disorder" was coined. 

Egypt, Japan, China and several European countries have since reported large-scale loss of bee populations.