From the 1950s through the end of the Cold War, the US Navy has maintained an extraordinary network of secret undersea hydrophone arrays known as the SOound SUrveillance System (SOSUS). SOSUS was designed for monitoring the movements of submarines and surface ships throughout vast areas of the Atantic and Pacific oceans by detecting and tracking the vessels' low-frequency sounds (<1000 Hz). SOSUS is part of the larger Integrated Undersea Surveillance System (IUSS).

Since 1993, scientists from the Bioacoustics Research Program (BRP) have been granted access to parts of the IUSS network for studies on whales. The initial logic was simple. Since the system works best for low-frequency sounds and many whales produce low-frequency sounds, can the network be used to detect, count, and track vocalizing whales? The answer was a resounding YES! In the first afternoon, witht the help of Navy analysts, more blue whale sounds were detected than had been described in the entire collection of scientific papers. Within a day we had confirmed detections of blue, fin, humpback, and minke whales. The long, patterned sequences of blue and fin whale sounds can sometimes be detected by SOSUS at distances in excess of 1500 nautical miles (approximately 3000 km). Humpbacks are detectable over distances of a few hundred miles, and minkes over distances of up to a hundred miles.

None of the accomplishments presented here would have been possible without the remarkable support and guidance of Navy personnel. Beginning in 1993, using acoustic data from IUSS, we have studied the seasonal and geographic patterns of vocal activity for blue, fin, humpback, and minke whales from large portions of the western North Atlantic (east of the Canadian maritime provinces and the US eastern seaboard) and eastern North Atlantic (west of Britain and Ireland).

		Figure 1. Sound spectrograms of sample vocalizations from four species of large baleen whales in the western north Atlantic, made from sounds obtained from the IUSS system.

(To hear the sounds that correspond to spectrograms such as these, click here.)

All four species exhibit annual cycles of calling.

		Figure 2. An example plot of the daily counts of finback whales for three years, at one site in the western North Atlantic. The annual pattern of vocal activity is evident.

The whale detection data collected from the IUSS have provided the first ocean-scale view ever compiled on the distribution of whale vocal activity. These studies are unprecedented both in their geographical scope and in their level of detail. They demonstrate the unique power of existing IUSS assets to simultaneously collect large quantities of acoustic data on numerous individual whales across a vast geographic area. Such studies could not be undertaken without access to IUSS resources.

Figure 3, a map of the Atlantic Ocean and the track of an individual blue whale, tracked for 43 days with the IUSS system by Navy personnel, is a small demonstration of the types of data available from so powerful an underwater listening system.

			Figure 3. Map of Atlantic Ocean and the track of a Blue Whale, tracked for 43 days with the IUSS system by IUSS personnel. Map provided by Dr. Clyde Nishimura of the Naval Research Lab.

The use of IUSS to monitor whale vocalizations in the western North Atlantic has been funded by the US Office of Naval Research and the Naval Research Laboratory. IUSS whale monitoring work in the eastern North Atlantic has been funded by the Atlantic Frontier Environmental Network through the (UK) Joint Nature Conservation Committee. We thank these sponsors, and the many talented, capable, and enthusiastic personnel within the US Navy without whose skills and support this work would not have been possible.