With more than 300 extremely quiet diesel-electric submarines patrolling the oceans, operated by more than 40 nations worldwide, anti-submarine warfare is a top warfighting and training priority for the Navy.
As a part of the Navy’s annual training exercises, ships can deploy powerful sonar to locate submarines, producing sound waves that can travel across hundreds of kilometers of ocean and possibly disrupt the communication and feeding of marine mammals.
In September 2015, the Navy committed to limit its use of sonar and other activities which may unintentionally impact cetaceans and other marine mammals in specified habitats around the Hawaiian Islands and southern California.
These areas are known to be vital to marine mammals for reproducing, feeding, and migrating; some also harbor small, resident populations of animals. A prime feeding area for blue whales is found in the waters near San Diego, with rare beaked whales found in the waters between Santa Catalina and San Nicolas islands and Hawaii’s Pacific Missile Range Facility.
Attempts to predict and mitigate the effects of noise are hampered by a lack of knowledge regarding the actual numbers of whales that may be inhabiting Navy testing and training ranges, and regarding the manner in which these animals are likely to react to Navy sound sources.
SSC Pacific’s role
The Novel Active Acoustic Tag for Tracking Whales applied research project is a SSC Pacific effort to support the Navy’s requirement to monitor responses of marine mammals to sonar activities, reduce environmental impacts, and improve the Navy’s ability to predict and mitigate the effects of anti-submarine warfare activities on baleen whales.
The goal of SSC Pacific bioacoustic scientist Elizabeth Henderson is to develop an active acoustic pinger that will assist in the detection of the locations, movement patterns, and vocalization rates of whales for assessment, relative to Navy testing and training activities in order to fill important data gaps.
The proposed effort would allow baleen whale presence, vocalization rates, and behavior to be quantified and correlated with naval training and testing activities on instrumented ranges, which would improve whale density estimates and the Navy’s ability to understand the behavioral responses of whales to sonar and other Navy sound sources.
According to the National Oceanic and Atmospheric Administration, baleen whales are the largest animals on earth, yet they feed on some of the smallest animals in the ocean. There are 12 baleen whale species divided into four families, including right, pygmy right, gray and rorqual whales.
The results of SSC Pacific’s efforts could lead to more accurate acoustic impact assessments in Navy environmental studies and better support the Marine Mammal Protection Act (MMPA) and Endangered Species Act (ESA).
The pinger tag creates a repeated high-frequency ping outside the range of the whale’s hearing that can be detected on the range hydrophones and used to track the whales when they are not vocalizing.
Marine mammals produce a variety of vocalizations, primarily for communication, although the toothed whales produce echolocation clicks, a type of sonar used to navigate and find prey. Baleen whales produce very low frequency vocalizations, some even below the level of human hearing. Low frequency sounds travel farther in water, and therefore these calls are likely used to communicate across long distances.
Humpback whale males, for example, will often sing for extended periods of time, and researchers can track their position by localizing the whale using their song. However, if they cease singing they can no longer be tracked. This is where the pinger comes into play: researchers can track the pings instead of the vocalizations.
A time/depth recorder in a separate satellite tag records information as the whale is diving. When the whale is at the surface, the tag uplinks the data through the satellites. Care is being taken during testing to ensure that the whales themselves do not hear the pinger, and that any cetaceans that would hear it (such as dolphins) are not bothered by it.
The way ahead
Testing is planned to take place in Hawaii. The pinger tag will initially be attached temporarily using suction cups, so the tag could fall off within a matter of minutes to hours. This allows for additional testing to ensure no unforeseen responses occur. If the initial tag testing phase is successful and creates no response in the whales while proving effective at tracking, then future tags could be attached using small titanium darts that last for weeks to months.
Because the tag is intended to be outside of the hearing capabilities of the whale, it does not negatively impact the whales. Navy scientists can then monitor marine mammal movement patterns effectively during Navy testing and training activities utilizing active sonar.
The Navy, as a world leader in marine mammal research, conducts extensive research to better understand marine mammals in order to best protect them while meeting national security objectives. The Navy’s research community is dedicated to building and strengthening one of the world’s most robust research programs designed to improve the understanding of marine mammal ecology and population dynamics, to determine potential effects of man-made sound, and to monitor for marine mammal presence.