The effects of mining machinery noise of different frequencies on the behaviour, faecal corticosterone and tissue morphology of wild mice (Mus musculus)

Mining noise has a wide variety of frequency spectra and is a potential source of stress for wildlife. We evaluated the effects of mining machinery noise on behaviour and associated physiological parameters at two isoenergetic frequency ranges: high (> 2 kHz) and low (<= 2 kHz), the latter being less audible to mice, our model species. Effects of these two frequency spectra on behaviour, organ morphology and faecal corticosterone of wild mice were compared with a control treatment with no extra auditory stimuli. The mice exposed to high frequency noise spent less time in their nest than those exposed to low frequency noise or those in the control treatment, and they spent more time circling, especially anticlockwise, which in conjunction with elevated faecal corticosterone levels may reflect a greater right brain hemisphere stress-related response, particularly in females. Low frequency mining noise reduced grooming and circling, suggesting decreased physiological arousal due to mild stress. Low frequencies were also associated with increased faecal corticosterone in males compared to controls, which may be related to gender-based differences of the ear canal that affect frequency sensitivity. In conclusion, high frequency and low frequency mining machinery noise produced stress-related responses that may be important for the animals' welfare and survival.