Putative contact calls made by humpback whales (Megaptera novaeangliae) in southeastern Alaska

Abstract

Describing the acoustic properties and usage patterns of whale vocalizations is essential for documenting their functions and biological importance. Here the authors describe the acoustic characteristics and patterns of occurrence of the most common vocalization of the humpback whale (Megaptera novaeangliae) on its southeastern Alaska summer feeding grounds; a simple frequency-modulated call referred to as the “whup”.  The authors examined 59 randomly selected days of continuous data recorded from an anchored hydrophone in Glacier Bay National Park from May through September 2007-2010. Using an automated detector 1,336 whups were identified, and their physical characteristics measured.  Two distinct components of each whup were measured: a low-frequency growl with a fundamental tone, and a broadband upsweep.  The growl component averaged 0.47 sec duration, within a 56-187 Hz frequency range, and had a peak frequency of 94 Hz.  The upsweep component averaged 0.19 sec duration over a broadband frequency range of 52-743 Hz, with a peak frequency of 93 Hz.   Of the 1,336 whups identified, 61% were in multiple-call groupings. Whups were significantly more likely to occur at night than during the day (t= -2.647, df=22, p=0.0147). Due to its patterns of usage and acoustic similarity to other mysticete contact calls, the authors speculate that inter-group communication is the main function of this call.