Blue whale vocalizations recorded around New Zealand: 1964–2013

Abstract

Previous underwater recordings made in New Zealand have identified a complex sequence of low frequency sounds that have been attributed to blue whales based on similarity to blue whale songs in other areas. Recordings of sounds with these characteristics were made opportunistically during the Southern Ocean Research Partnership's recent Antarctic Blue Whale Voyage. Detections of these sounds occurred all around the South Island of New Zealand during the voyage transits from Nelson, New Zealand to the Antarctic and return. By following acoustic bearings from directional sonobuoys, blue whales were visually detected and confirmed as the source of these sounds. These recordings, together with the historical recordings made northeast of New Zealand, indicate song types that persist over several decades and are indicative of the year-round presence of a population of blue whales that inhabits the waters around New Zealand. Measurements of the four-part vocalizations reveal that blue whale song in this region has changed slowly, but consistently over the past 50 years. The most intense units of these calls were detected as far south as 53°S, which represents a considerable range extension compared to the limited prior data on the spatial distribution of this population.

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Blue whale song around New Zealand differs from the Western Australian pygmy blue whale song [83,98,99]. The typical sequence of units comprises two consecutive AM tones with associated harmonics, followed by an upsweep.…”

Validating the reliability of passive acoustic localisation: a novel method for encountering rare and remote Antarctic blue whales

“…Analysis of the bearings to sound sources followed the methods of Miller et al (2012Miller et al ( , 2013Miller et al ( , 2014. This involved a series of signal-processing steps on saved audio clips performed via a suite of MATLAB scripts.…”

“…This involved a series of signal-processing steps on saved audio clips performed via a suite of MATLAB scripts. Signal processing included the 'validation' of the sono buoy compass and measurement of a compass correction for each sono buoy as described in Miller et al (2012Miller et al ( , 2013Miller et al ( , 2014. The final output was a true bearing from the sonobuoy to the sound source of interest.…”

Documentation of a New Zealand blue whale population based on multiple lines of evidence

“…The pygmy blue whales found in the Indian Ocean and off Australia appear to have diverged from Antarctic blue whales around the last glacial maximum and are genetically, acoustically, and morphologically distinct from Antarctic and Chilean blue whales (Branch et al 2007, Miller et al 2014, Attard et al 2015. Under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, Antarctic blue whales are classified as 'Critically Endangered' (Reilly et al 2008), and pygmy blue whales are listed as 'Data Deficient' (Cetacean Specialist Group 1996).…”