Vibrational noise pollution in bee hives generated by railway traffic

Anthropogenic noise pollution has become a threat for the fauna with possible effects on animal physiology and behaviour. We explored the effects of anthropogenic vibrational noise on honey bees (Apis mellifera). The intensity of substrate borne vibrations generated by trains on the ground, on the front comb of a hive and on its base as well as the airborne sound pressure were recorded at different distances and sites. Vibrational noise of amplitudes that can be detected by honey bees is present on the ground surface, on the comb and on the base over distances up to 20 m from the railway track and the attenuation of the airborne sounds is higher than the attenuation of the substrate borne vibrations. Bees placed in an observational hive and exposed to simulated substrate borne vibrations caused by a cargo train show significant behavioural reactions. The same substrate borne vibration was presented to bee colonies every 5 minutes continuously for six months at realistic amplitudes. On the colony level no differences are found for capped and open worker brood, worker eggs, adult drone population, capped and open drone brood, brood development, varroa mites, collected pollen and honey production; while some significant differences are present for worker population and pollen collecting foragers. We conclude that honey bee colonies in the vicinity of railroads are exposed to substrate borne vibrational noise above their threshold of sensitivity up to 20 m. At the individual level bees show reactions to the vibrations; however, at the population level bees seem to cope with the disturbance. As higher amplitudes and additional stress factors might affect the colonies, it seems to be anyways advisable to generally avoid placing bee colonies close to anthropogenic vibrational noise sources.