• India’s Ganga River is getting noisier with increased ship traffic and dredging, and that’s stressing the river’s iconic dolphins and changing how they communicate, a new study has found.
• When fewer than five vessels moving on the river per hour, the dolphins seem to enhance their vocal activities to compensate for the high-frequency noise generated by the propellers.
• But as vessel traffic increases and water levels fall during the dry season, leading to more intense and sustained noise pollution, the dolphins don’t seem to alter their clicks much compared to baseline levels, the researchers found.
• This is likely because having to continuously emit clicks in a persistently noisy world can be physically taxing, forcing the endangered mammals to “either call at baseline levels or shut up,” according to the researchers.

Mongabay