Scientists from Marine Ecology and Telemetry Research (MarEcoTel) and a team of collaborators have just released the findings of a new study into how whales are affected by military sonar in the journal Royal Society Open Science. This study focused on Cuvier’s beaked whales that live off the coast of Southern California in an area the US Navy frequently uses for training exercises. This is the species most frequently observed to strand in association with sonar use in other parts of the world. Using small, dive-recording satellite transmitters attached to the whales’ fins, they monitored the behavior of 16 whales for periods up to several months, allowing a comparison between how whales behaved when military sonar systems were active and when not in use. This study provided the first large sample of whale behavior with known exposures to ship sonar, which have been studied previously, and to helicopter-deployed sonar that has received much less attention because it is considerably quieter than the sonar used by ships. It also allowed researchers to identify the range of distances to sonar that whales changed their behavior.
A variety of behavioral changes were observed, including increased dive duration and an increase in the amount of time between the very deep dives these whales conduct when they are searching for food near the ocean floor. Some of these behavior changes were evident when sonar was used up to 100 km away, though they became more pronounced the closer the sonar was to the whale. One surprising finding was that whales tended to respond more strongly to the quieter helicopter-deployed sonar than to ship sonar at a similar distance. In fact, one whale dove for an astonishing 2 hours and 43 minutes, a new mammalian diving record, while a helicopter deployed its sonar nearby. The authors suggest that these whales may respond more strongly to helicopter-deployed sonar because it is used in a less predictable way.
While none of these whales, who appear to preferentially use this region despite the regular disturbance, stranded or died as a result of sonar use during the course of the study, these findings underscore the importance of understanding what these responses mean for the health of both individuals and populations over time. They also suggest that in an area where whales are frequently exposed, the context of sonar is a potentially important predictor of behavior in addition to sound level, which is how sonar impacts are currently estimated.
A copy of the paper can be downloaded here (Falcone et al. 2017), or by going to the Royal Society Open Science Website (Falcone et al. 2017).
For more information, please contact Erin Falcone (email@example.com) or Greg Schorr (firstname.lastname@example.org)
An adult male Cuvier's beaked whale surfaces to breath. Mature males in this species have two small, conical teeth that erupt from the tip of the lower jaw; this whale has stalked barnacles growing from his teeth. Males use their teeth to fight with one another, and older males, like this one, will become covered with long, linear scars as a result. The yellowish coloration on this whale is caused by a type of algae that grows on the whales' skin.
We just completed our fourth field effort of 2017. This was our third trip down to San Clemente Island this year. This is a continuation of our long-term study on potential impacts of military activities on beaked whales and other species. The U.S. Navy’s Southern California Anti-Submarine Warfare Range (SOAR), which extends west into the San Nicolas Basin from San Clement Island, is a focal training area within the Southern California Offshore Complex (SOCAL). SOAR consists of an array of 88 bottom-mounted hydrophones that are used for real-time, three-dimensional tracking of undersea vehicles. During this project, we work closely with M3R (Marine Mammal Monitoring on Navy Ranges). Acousticians monitor these hydrophones looking for vocalizing beaked whales and other species to identify areas where we should focus our efforts. Beaked whales vocalize during deep foraging dives. M3R tracks the locations where the vocalizations are occurring to provide the best opportunity for us to locate these animals once they have ceased foraging at depth and return to the surface.
This survey effort took place from July 22-30th. During that time, we surveyed 666 nautical miles and spent over 70 hours on the water searching for whales and dolphins. In total, we documented seven species: Cuvier’s beaked whale, humpback whale, short-beaked and long-beaked common dolphin, bottlenose dolphin, bryde’s whale, and fin whale. It was rather quiet for large whales during this survey. We documented one humpback whale, five fin whales (two mom/calf pairs), and a Bryde’s whale. Bryde’s whales are infrequently sighted so we were very excited to document the presence of this animal. While it was pretty quiet for large whales, we were quite successful in locating beaked whales. In all, we had five encounters totaling 9 unique individuals including 2 calves. We started out the trip with some luck as we documented our first encounter of beaked whales on the very first day on the water as we surveyed from the coast out to the island. Later in the week, we were able to deploy a satellite tag on an adult male. In addition to recording dive behavior and locations, this tag provides superior location estimate over a standard Argos tag with the inclusion of Fastloc fast-acquistion GPS developed by MarEcoTel and Wildlife Computers as part of a project in collaboration with the Naval Undersea Warfare Center and was funded by the Environmental Security Technology Certification Program. This was our third deployment of this type of tag on a Cuvier’s, all occurring this year. When we relocated this animal four days later, he was still associated with the same individual from the tagging day as well as a new one. In addition to quality photographs of all animals, we collected nine water samples from the footprints to contribute to a study looking at environmental DNA conducted by the University of Oregon. An additional five biopsy samples were collected from bottlenose and common dolphins to contribute to ongoing studies.
Funding for this research was provided by the U.S. Navy Pacific Fleet. Our next field effort will occur in November and we will be back on San Clemente Island.