Weak anthropogenic electric fields affect honeybee foraging.

Bees tend to acquire a positive electrostatic charge while flying. In contrast, flowers are usually negatively charged due to their electrical connection to the ground and the generally positive atmospheric potential gradient. These charge dynamics create an electrical environment that provides foraging signals and facilitates pollen transfer. Animal pollination is responsible for approximately 75% of food crops and 35% of global food production, which is estimated to have an annual economic value of between 235 billion and 577 billion US dollars. The following study investigated how visits by honeybees to flowers are influenced by small electric fields generated on site, making this a semifield study.

Field experiments were conducted in Bristol, UK, to study the impact of weak anthropogenic electric fields on pollinator behavior. Researchers manipulated the electrical environment of flowers by exposing them to electric fields that mimicked the alternating and direct current voltages of transmission lines. Then, they observed how honeybees landed. The electric fields were generated near 2 catnip flowers (1.2 meters apart) using a portable, battery-powered function generator. The researchers simultaneously observed the foraging behavior of the honeybees at 2 flowers, focusing on how they landed on the exposed flower and the (sham-exposed) control flower.

In an experiment in which electric fields were altered, the average number of bees that landed on flowers exposed to alternating or direct current fields decreased by 70.8% and 52.6%, respectively, compared to flowers in the control group. In contrast, no difference in landing numbers was observed with negative DC treatment. Regarding temporal variation in observed behavior, the number of bees that landed on flowers exposed to AC treatment during the first 10 minutes was 5.9% of what was observed for the paired control flower. This figure increased to 58.8% in the subsequent 10 minutes. This effect was less pronounced for DC fields. The AC field used in this experiment corresponds to ambient electric fields at a distance of about 100 meters from a 275 kV high-voltage transmission line.

This study shows that weak, locally limited anthropogenic electric fields with strengths comparable to those measured 50 to 150 meters away from high-voltage transmission lines alter the foraging behavior of honeybees. Therefore, it is conceivable that such fields could influence the foraging behavior of pollinators and their interactions with flowers. However, the experimental electric fields used in this study were constant in strength and dynamics, representing a stable stimulus. In contrast, anthropogenic electric fields often fluctuate considerably in strength due to variable power consumption throughout the day. In addition, these results focus on short-term effects. Further research is needed to understand how these responses can be applied to different pollinators, plant species, and broader ecological networks. (AT)