Smartphone-based sound level meter application for monitoring thermal comfort of honeybees Apis mellifera L

Abstract

ABSTRACT As thermoregulatory behaviors produce audible sounds, we sought to answer the following questions: (a) can a smartphone-based sound level meter application detect changes in the sound intensity level (SIL) of Apis mellifera hives? (b) Does the SIL reflect the hive microclimate? (c) Can analysis of the bees’ behavior help to detect thermal stress? We monitored the daily variation of the internal (Tin) and external hive temperatures (Tair), SIL, and the numbers of incoming (Fin) and outgoing (Fout) honeybees in three thermal environments: natural (T0) and controlled at 33°C (T1) and 40°C (T2). Hive overheating was observed in the T2 hive, and high and constant SIL was recorded. In T1, Tin oscillated depending on Tair, increasing slightly above the upper limit of the optimal range when Tair increased. We detected elevations in SIL at the times points when Tin increased. The Fout was lower in treatments where there was an increased need to warm the nest (T0 and T1). The Fin was more intense in the early morning, and the incoming of bees was highest in T2 followed by T1 and then T0. In conclusion, this technology allowed detection of SIL changes associated with even slight increases in Tin above the optimal range.