Abstract
The vocalization behavior of humpback whales was monitored over vast areas of the Gulf of Maine using the passive ocean acoustic waveguide remote sensing technique (POAWRS) over multiple diel cycles in Fall 2006. The humpback vocalizations comprised of both song and non-song are analyzed. The song vocalizations, composed of highly structured and repeatable set of phrases, are characterized by inter-pulse intervals of 3.5 ± 1.8 s. Songs were detected throughout the diel cycle, occuring roughly 40% during the day and 60% during the night. The humpback non-song vocalizations, dominated by shorter duration (≤3 s) downsweep and bow-shaped moans, as well as a small fraction of longer duration (∼5 s) cries, have significantly larger mean and more variable inter-pulse intervals of 14.2 ± 11 s. The non-song vocalizations were detected at night with negligible detections during the day, implying they probably function as nighttime communication signals. The humpback song and non-song vocalizations are separately localized using the moving array triangulation and array invariant techniques. The humpback song and non-song moan calls are both consistently localized to a dense area on northeastern Georges Bank and a less dense region extended from Franklin Basin to the Great South Channel. Humpback cries occur exclusively on northeastern Georges Bank and during nights with coincident dense Atlantic herring shoaling populations, implying the cries are feeding-related.
Highlights
The diel vocalization behavior of Northwestern Atlantic humpback whales (Megaptera Novaeangliae) was monitored over vast areas of the Gulf of Maine using the passive ocean acoustic waveguide remote sensing (POAWRS) technique [1,2,3] from 19 September to 6 October 2006
The humpback vocalizations measured by the passive ocean acoustic waveguide remote sensing technique (POAWRS) receiver array from 27 September to October 2006 are plotted in Figure 1 as a function of measured bearing and time
70% of humpback vocalizations arise from bearing ranges 90◦ –130◦
Summary
The diel vocalization behavior of Northwestern Atlantic humpback whales (Megaptera Novaeangliae) was monitored over vast areas of the Gulf of Maine using the passive ocean acoustic waveguide remote sensing (POAWRS) technique [1,2,3] from 19 September to 6 October 2006. Humpback vocalizations were measured using a large-aperture densely-sampled coherent hydrophone array system at a rate of approximately 1800 ± 1100 calls per day occurring in the 100–1000 Hz frequency range. We provide representative beamformed spectrograms of the detected humpback song and non-song vocalization sequences, and quantify the temporal-spectral characteristics that distinguish them. Humpback song sequences are identified as those composed of repeatable themes or patterned set of phrases [2,5,6,7,8], where each phrase is composed of units with distinctive time-frequency characteristics. Calls and call sequences without a repeatable theme or patterned set of phrases were categorized as non-song.
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