The 3S3 experiment data report - using operational naval sonars to study the effects of continuous active sonar, and source proximity, on sperm whales

The 3S project is an international collaborative effort with the aim to investigate behavioral reactions of cetaceans to naval sonar signals. The objectives of the third phase of the project (3S3) were to investigate if exposure to continuous active sonar (CAS) leads to different types or severity of behavioral responses than exposure to traditional pulsed active sonar (PAS) signals, and to investigate how the proximity of the source to a whale affects behavioral responses. This report summarizes the method and data collected during the 3S-2016, 3S-2017 and 3S-2019-OPS research trials.

We worked on and off the shelf break between Harstad and Tromsø in Norway. Sperm whales and pilot whales were the primary target species. When a target species was localized, a tag boat was launched and DTAG or mixed-DTAGs deployed. The mixed-DTAG contained a GPS, an Argos satellite transmitter, in addition to the core DTAG unit with triaxial accelerometers and magnetometer sensors, stereo acoustic sensors and a pressure sensor. In addition to the tags, additional acoustic data were collected by two moored acoustic buoys, for assessment of potential vocal responses and avoidance of the exposed area. Tagged whales were subject to controlled sonar exposure experiments (CEE). The experimental design involved dose escalation at different ranges and maximum source levels using operational sources towed by the FFI research vessel H.U. Sverdrup II (HUS) or the Norwegian Navy frigate KNM Otto Sverdrup (OSVE). The experiments were conducted under permit from the Norwegian Animal Research Authority, and all procedures were approved by the Animal Welfare Ethics Committee at the University of St Andrews. A separate risk assessment and management plan was developed for the trial to minimize risk to the environment and third parties.

During a total of 9 weeks at sea we tagged 33 sperm whales and collected 630 hours of tag data. We conducted 24 controlled exposure experiments with 71 sonar or control sessions. 7 CEEs with 16 sessions were conducted using the frigate OSVE as the source vessel. In addition, 8 long-finned pilot whales were tagged, but tag durations were generally short and only 2 CEE sessions were conducted. Only the sperm whale data is reported here. Data plots of all collected data are presented, with a summary of key experimental outcomes. Further analysis and interpretation of the data will be presented in already published or scientific papers in preparation.

We expect that the data collected will be sufficient to achieve the objectives of the 3S3 project and answer the questions of CAS versus PAS and received level versus range conclusively for sperm whales. This knowledge will increase our ability to do risk assessment on new CAS technology and to assess how experimental data from CEEs using scaled sources can be used to predict responses from real naval sonar scenarios. Remaining questions for future research include how CAS affects the behavior of other species, particularly species more sensitive to PAS, and whether habituation or sensitization might occur during longer duration exposures that are more realistic.

A video showing the activities during the 3S3 experiments can be seen following this link.

The data plots in Appendix B can be downloaded here. The file is approximately 130 Mb.