Source levels of foraging humpback whale calls

Area of Science:

• Marine Biology
• Bioacoustics
• Animal Communication

Background:

• Humpback whales (Megaptera novaeangliae) utilize diverse vocalizations, with non-song calls prevalent on foraging grounds.
• Understanding the acoustic properties of these calls is crucial for marine mammal research and conservation.

Purpose of the Study:

• To estimate the source levels of humpback whale non-song vocalizations on high-latitude foraging grounds.
• To compare source levels across different vocal classes within the species' repertoire.

Main Methods:

• Acoustic data were collected using a four-element planar array in Glacier Bay National Park and Preserve, Southeast Alaska.
• Source levels of 426 humpback whale calls, categorized into four vocal classes, were estimated.
• Source levels were measured in dB RMS re 1 µPa @ 1m within the call's bandwidth.

Main Results:

• No significant difference in source levels was found among the four humpback whale vocal classes.
• The mean call source level was determined to be 137 dB RMS re 1 µPa @ 1m (range: 113-157 dB RMS re 1 µPa @ 1m).
• Bandwidth was defined as the frequency range from the lowest to the highest frequency component of the call.

Conclusions:

• The estimated mean source level of 137 dB provides a robust measure for humpback whale calls on foraging grounds.
• These findings supplement and enhance previous estimates of humpback whale vocal source levels.
• The study contributes valuable data to the field of marine bioacoustics and understanding humpback whale communication.