Assessing shipping noise as a potential driver of harbour seal (Phoca vitulina) habitat selection

Over the past decade, anthropogenic noise from activities such as shipping has significantly increased in the ocean, raising questions on their potential impact on coastal species such as harbour seals. In this study, we assessed the spatial overlap between ships (equipped with AIS transmitters) and harbour seals (tracked using telemetry) in the English Channel, one of the densest shipping areas in the world. We then studied how their habitat selection varied according to environmental parameters taking into account shipping noise as a potential driver. A total of 28 harbour seals were captured and equipped with GPS-GSM tags. AIS data (ships > 15 m length) was used to estimate shipping traffic density and model the associated shipping noise. We then used generalised additive mixed models to assess harbour seals’ habitat selection using distance to haulout, distance to shore, bathymetry, tidal current, sediment type, and shipping noise as explanatory variables. The model selected had an explained deviance of 71.8%. Our findings indicate that distance to haulout sites was the primary driver of habitat selection (~91.5% deviance), while other environmental factors such as bathymetry (~4.4%), distance to shore (~3.1%), tidal current (~0.3%), sediment type (~0.6%), and shipping noise (~0.1%) had only minor influences on their selection. Despite a high spatial overlap between shipping activity and tracked seals (73% of overlap), the weak contribution of shipping noise suggests that either seals may be habituated to chronic noise exposure or that noise levels rarely exceed tolerance threshold levels. To the best of our knowledge, this is the first article integrating shipping noise into harbour seals’ habitat selection models. These findings provide an understanding of harbour seal habitat selection in anthropogenic environments.