Tim Stephens, 8 July 2022.

Excerpt:

>The reaction of narwhals to the loud noise from seismic air guns used in oil exploration involves a disruption of the normal physiological response to intense exercise as the animals try to escape the noise. The overall effect is a large increase in the energetic cost of diving while a paradoxically reduced heart rate alters the circulation of blood and oxygen.

>“They’re swimming as hard as they can to get away, and yet their heart rate is not increasing—we think because of a fear response. This affects how much blood and oxygen can circulate, and that’s going to be problematic,” said Terrie Williams, a professor of ecology and evolutionary biology at UC Santa Cruz who led the new study.

>Published July 8 in the Journal of Functional Ecology, the study provides the first look at the impact of seismic noise on the physiological responses of a deep-diving cetacean.

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>According to Williams, the combination of extremely low heart rates, increased heart rate variability, and high-intensity exercise during deep dives presents a significant physiological challenge for narwhals, especially if the disruptions are prolonged as would be likely during extended oil exploration activities.

>Narwhals live year-round in high Arctic waters where sea ice has helped isolate them from disturbance by humans for millions of years.

>But declines in polar sea ice are making the region more accessible to shipping, natural resource exploration, and other human activities.

Journal of Functional Ecology, 2022. DOI: 10.1111/1365-2435.14119