Marine Mammal Research
The U.S. Navy is a global leader in marine mammal research, helping to better understand the relationship between humans and these complex creatures.
The U.S. Navy is legally mandated to assess the potential effects of all training and testing activities on marine life, but definitive studies on the response of marine mammals to anthropogenic sound are hampered by the short surface time and deep-diving lifestyle of many species. In the past two decades, rapid advances in the transmitters, receivers, and data storage tags that are attached to animals have made it possible to collect high-quality biological and oceanographic observations on timescales varying from days to years. The Office of Naval Research (ONR) has supported biologist Dr. Peter Tyack and engineer Mark Johnson (both formerly at Woods Hole Oceanographic Institute) since early in the 2000s to better understand the effects of Navy sonar on marine mammals.
A Blue whale is pole-tagged with a Dtag off southern California.
(Photo courtesy of Ari Friedlaender, NMFS permit #19116)
The results have been a resounding success. Tyack and Johnson partnered to develop what would become known as the “Dtag,” or digital recording tag, which to this day—now in its third generation—is the most sophisticated tag available for marine mammals.
The Dtag is noninvasive (attached to the whales with suction cups) and contains solid-state memory. It records continuously from a built-in hydrophone and a suite of sensors. The sensors sample the orientation of the animal in three dimensions with sufficient speed and resolution to capture individual fluke strokes. Audio and sensor recording is synchronous, so the relative timing of sounds and motion can be determined precisely.
The Dtag has revolutionized our understanding of marine mammal movement and behavior, and led to the development of an active field of research to better understand and assess the potential behavioral effects of Navy activities on marine mammals.