Classification of narwhal (Monodon monoceros) calls and changes in rates of calling associated with passing ships in Milne Inlet, Nunavut, Canada

Abstract

My study is part of an environmental monitoring program to assess potential impacts from increased shipping noise disturbance on narwhal (Monodon monoceros) vocalization behaviours on their summering grounds in 2018-2019, in Koluktoo Bay and Milne Inlet, Nunavut, Canada. A complete call repertoire was established using sounds recorded from passive acoustic monitors and acoustic tags attached to individual narwhals. Five major call types were identified: Buzzes, Echolocation Clicks, Knocks, Whistles, and a patterned Double Buzz. Buzzes, Knocks, and Whistles (all social calls) were used to determine if changes to narwhal calling rates occurred in the presence of ore carrier noise. When ship noise was above ambient noise levels, call counts were lower but returned to normal shortly after ship passages. Decreases in calling rates occurred within line-of-sight of the ship (±5 km) with no association to any amplitude threshold (dB level). Minimizing ship noise exposure durations should be undertaken whenever possible.