Increased aggression and reduced aversive learning in honey bees exposed to extremely low frequency electromagnetic fields

Abstract

Honey bees, Apis mellifera, are a globally significant pollinator species and are currently in decline, with losses attributed to an array of interacting environmental stressors. Extremely low frequency electromagnetic fields (ELF EMFs) are a lesser-known abiotic environmental factor that are emitted from a variety of anthropogenic sources, including power lines, and have recently been shown to have a significant impact on the cognitive abilities and behaviour of honey bees. Here we have investigated the effects of field-realistic levels of ELF EMFs on aversive learning and aggression levels, which are critical factors for bees to maintain colony strength. Bees were exposed for 17 h to 100 μT or 1000 μT ELF EMFs, or a sham control. A sting extension response (SER) assay was conducted to determine the effects of ELF EMFs on aversive learning, while an intruder assay was conducted to determine the effects of ELF EMFs on aggression levels. Exposure to both 100 μT and 1000 μT ELF EMF reduced aversive learning performance by over 20%. Exposure to 100 μT ELF EMFs also increased aggression scores by 60%, in response to intruder bees from foreign hives. These results indicate that short-term exposure to ELF EMFs, at levels that could be encountered in bee hives placed under power lines, reduced aversive learning and increased aggression levels. These behavioural changes could have wider ecological implications in terms of the ability of bees to interact with, and respond appropriately to, threats and negative environmental stimuli.

Effect of Rearing Queen Bees, Apis mellifera L. Raised from Grafted Larvae Under Magnetic Field Conditions on Its Characteristics

“…These data agreed with FCC, (1999), Hsu, and Li (1994), Harst, et al (2006), Stever, et al (2007, Kumar, et al (2010), Sharma and Kumar (2010), Sainudeen (2011), Kumar et al (2013) and Shepherd et al (2019)…”

Extremely Low‐Frequency Electromagnetic Fields Entrain Locust Wingbeats

“…The fields produced by HVTLs are dynamic and vary in intensity at 50 Hz [WHO, 2007]. In previous studies [Shepherd et al, 2018[Shepherd et al, , 2019, we mapped the EMF generated by the coils and modeled the EMF generated around HVTLs [Shepherd et al, 2018]. Due to the small physical dimensions of the coils, using a meter to map the EF strength was inaccurate.…”

“…Pellacani and Costa [2018] describe the range of biological effects that ELF EMF pollution causes, including neurological effects that underpin behavioral processes in a variety of organisms. In addition, ELF EMFs can have profound effects on the behavior and cognition of insects [Maliszewska et al, 2018;Shepherd et al, 2018Shepherd et al, , 2019. Important pollinator species, such as honeybees, use low-strength magnetic fields as cues for foraging [Chicas-Mosier et al, 2020].…”

“…Important pollinator species, such as honeybees, use low-strength magnetic fields as cues for foraging [Chicas-Mosier et al, 2020]. Exposure to 50 Hz EMFs, at levels honeybees may encounter from overhead powerlines in the environ-ment, reduces learning, aggression, and foraging flight [Shepherd et al, 2018[Shepherd et al, , 2019. Fifty-hertz electric fields (EFs) have also been shown to increase the activities of antioxidant systems in honeybees, including proteolytic and superoxide dismutase (SOD) systems [Migdał et al, 2020].…”

Effect of the electric field at 50 Hz and variable intensities on biochemical markers in the honey bee’s hemolymph

“…In addition, behavioral changes were compared with the activity of the proteases in the hemolymph of the bees [20]. Results of Shepherd et al [8,10] indicate that exposure to extremely low frequency (ELF) electromagnetic fields (EMFs) reduced aversive learning, alter flight dynamics, reduce the success of foraging flights towards food sources, and feeding, and increased level of aggression. The average levels of selected biochemical markers in the honey bee's hemolymph after bees exposure to the E-field at 50 Authors assumed that ELF electromagnetic fields at 50 Hz emitted from power lines may be an environmental stressor for honey bees, possibly altering their cognitive and motor skills, which could reduce their ability to pollinate crops [8].…”