Variation in harbour porpoise activity in response to seismic survey noise.
Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency.
Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK enrico.pirotta@abdn.ac.uk.
Enrico
E
Pirotta
Lighthouse Field Station, Institute of Biological and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL, UK Marine Scotland Science, Marine Laboratory, Aberdeen AB11 9DB, UK.
Kate L
KL
Brookes
Lighthouse Field Station, Institute of Biological and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL, UK.
Isla M
IM
Graham
Lighthouse Field Station, Institute of Biological and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL, UK.
Paul M
PM
Thompson
D000818:Animals; D001522:Behavior, Animal / Q000528:radiation effects*; D004455:Echolocation; D009622:Noise / Q000009:adverse effects*; D050741:Phocoena
activity budget; anthropogenic disturbance; environmental impact assessment; foraging efficiency