Assessment of thermodynamic and acoustic parameters in honeybee colonies under exposure to non-ionizing electromagnetic radiation

Abstract

Twenty-one clinically healthy honeybee colonies were monitored in a private apiary located in Vâlcea County, Romania, within an area influenced by electromagnetic fields (EMF) according to the National Authority for Management and Regulation in Communications (ANCOM) allocations. The site was situated below the activation threshold of the 5G n78 band (3.3–3.8 GHz), where mean field intensities of 12.74 mW/m² and peak values of 17.96 mW/m² were recorded. For each colony, five thermographic measurements were conducted (at the hive entrance, left lateral wall, rear wall, right lateral wall, and interior), totaling 105 recordings. During the inactive beekeeping season of 2025, strong colonies initiated winter clustering at approximately 7 °C, medium-strength colonies at 8 °C, and swarms at 10 °C, values consistent with the literature (7–10 °C). Thermographic analyses showed that only strong colonies consistently maintained the optimal internal range (32–36 °C), although peripheral zones exhibited peaks up to 52 °C. Medium-strength colonies displayed higher variability, with maxima of 52–55 °C, while swarms remained unstable, fluctuating around the minimum optimal temperature (≈25 °C) and frequently dropping to lower values (21–24 °C), confirming significant differences in thermoregulatory capacity among colony categories. Acoustic monitoring of the colonies revealed a nonlinear profile of sound level: ~36 dB at 50 m, maximum levels of 43–45 dB at 400–540 m due to reflections and interferences of EMF, and ~40 dB at 640–1000 m, with high variability influenced by terrain and nearby constructions.