| Summary: | Humpback whale "meow" vocalizations are characterized, classified and applied to derive humpback areal population density estimates. The "meow" vocalizations are the dominant calls recorded in the 300 to 700 Hz range using a coherent hydrophone array and previously found to be temporally and spatially synchronous with the formation of nocturnal Atlantic herring shoals in the Gulf of Maine. Here, each downsweep "meow" chirp is characterized by several features extracted from pitch tracking and then classified using K-means clustering. By accounting for the number of distinct "meow" clusters, the bearing-time trajectories concurrently observed for each cluster, and their corresponding localization areas, lower bound estimates of the nightly vocalizing humpback areal population density on the Northeastern flank of Georges Bank in Fall 2006 are derived. The humpback areal population density estimates derived here are in good agreement to those compiled from decades of visual surveys for the northern Georges Bank area. Unlike songs, which are uttered primarily by adult males, the humpback "meow" vocalizations are feeding related and likely uttered by all individuals regardless of gender or maturity. It is also shown that changes in humpback population composition can be monitored from changes in "meow" vocalization classification.
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