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

Mining noise has been identified as a source of stress for wildlife but the effects on the behaviour and physiology of individuals are largely unknown. We evaluated the effects of exposing wild mice to mining machinery noise for 3 weeks at two amplitude ranges: high (HA; 70-75 dB (A)) and low (LA; 60-65 dB (A)) on their behaviour, organ properties and faecal corticosterone levels, when compared with a control treatment (no extra auditory stimuli, below 55 dB (A)). Both noise treatments increased circling to the left, compared to the control (P = 0.001) which corresponds to right hemispheric processing of the stress response; however only the high amplitude noise increased circling to the right (left hemisphere activation; P < 0.0001), which may inhibit stress arousal by right hemisphere. Total circling behaviour (to the left and right) was just increased in mice exposed to high amplitude noise, compared with those in the control and low amplitude noise (P < 0.0001), but in the low amplitude noise faecal corticosterone was increased (P = 0.003). We hypothesize that dopamine-related stereotypies during high amplitude mining noise were a coping mechanism that prevented a physiological response. Noise-exposed males tended to have smaller spleens (P = 0.003) and females in the HA treatment tended to have a smaller adrenal cortex/medulla ratio (P = 0.007). Mining machinery noise produced amplitude - dependent stress responses in wild mice that probably required the generation of coping mechanism.