blue whale D calls **audible only with appropriate speakers**

This blue whale D-call series was recorded through a hydrophone on the Monterey Accelerated Research System (MARS) cabled observatory during hour 13 (UTC) of 18-July-2016. MARS is located at 36.7125N, 122.1869W on Smooth Ridge, which is on the continental slope west of Monterey Bay at approximately 900 m depth. Segments between calls were removed to shorten the recording and focus on variation of D-call attributes. This recording is of much higher quality than a shorter segment of D calls posted in this pack years ago. A subwoofer or good headphone set is required to hear these low-frequency vocalizations.

Bursts of blue whale D-call activity such as this have been associated with social foraging involving long-range acoustic communication. This behavior may enable a regional population of whales to share information about encounters with favorable foraging habitat, thus collectively sensing a vast and patchy habit to find the food resources they need to survive. For more information about this aspect of blue whale behavioral ecology, see https://www.sciencedirect.com/science/article/abs/pii/S000334722100316X.

For more information about the recording system, see https://www.mbari.org/technology/monterey-accelerated-research-system-mars/.