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Narwhals Repeatedly Strike Deep-Sea Hydrophones in Greenland Fjord, Study Finds

A peer-reviewed study reports bottom-moored hydrophones can attract narwhals, challenging the assumption that passive acoustic monitoring is nonintrusive.

Overview

  • Researchers documented 247 hit and rub incidents in more than 4,000 hours of audio from Inglefield Bredning Fjord between August 2022 and May 2024.
  • Accounting for ~15-minute recording gaps, the team estimated 484–613 actual hits during two months of narwhal presence, averaging about 10–11 per day mostly in daylight.
  • Interactions were captured on the two deepest moorings about 25 kilometers apart at roughly 190–400 meters, often following echolocation clicks and a foraging buzz.
  • Stomach analyses of 16 locally harvested narwhals showed a cod-dominated diet, supporting prey confusion as a plausible driver alongside possibilities like play or rubbing linked to molting.
  • The authors urge precautionary design adjustments such as shorter mooring lines and emphasize Indigenous collaboration for interpreting behavior and refining monitoring practices.