  Narwhals in the Arctic are increasingly exposed to human activities that can
temporarily or permanently threaten their survival by modifying their behavior.
We examine GPS data from a population of narwhals exposed to ship and seismic
airgun noise during a controlled experiment in 2018 in the Scoresby Sound fjord
system in Southeast Greenland. The fjord system has a complex shore line,
restricting the behavioral response options for the narwhals to escape the
threats. We propose a new continuous-time correlated velocity model with
varying coefficients that includes spatial constraints on movement. To assess
the sound exposure effect we compare a baseline model for the movement before
exposure to a response model for the movement during exposure. Our model,
applied to the narwhal data, suggests increased tortuosity of the trajectories
as a consequence of the spatial constraints, and further indicates that sound
exposure can disturb narwhal motion up to a couple of tens of kilometers.
Specifically, we found an increase in velocity and a decrease in the movement
persistence.
