Repeated call types in Hawaiian melon-headed whales (Peponocephala electra)

Abstract

Melon-headed whales are pantropical odontocetes that are often found near oceanic islands. While considered sound-sensitive, their bioacoustic characteristics are relatively poorly studied. The goal of this study was to characterize the vocal repertoire of melon-headed whales to determine whether they produce repeated calls that could assist in recognition of conspecifics. The first tag-based acoustic recordings of three melon-headed whales were analyzed. Tag records were visually and aurally inspected and all calls were individually extracted. Non-overlapping calls with sufficient signal-to-noise were then parameterized and visually grouped into categories of repeated call types. Thirty-six call categories emerged. Categories differed significantly in duration, peak and centroid frequency, and À3 dB bandwidth. Calls of a given type were more likely to follow each other than expected. These data suggest that repeated calls may function in individual, subgroup, or group recognition. Repeated call production could also serve to enhance signal detection in large groups with many individuals producing simultaneous calls. Results suggest that caution should be used in developing automatic classification algorithms for this species based on small sample sizes, as they may be dominated by repeated calls from a few individuals, and thus not representative of species-or population-specific acoustic parameters.

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

“…A series of broadband pulses is sometimes called a bout of pulses in the literature, other times an amplitude-modulated (AM) sound, and, if the analysis window is longer than the pulses, the sound looks tonal in spectrograms. To make this even more interesting, some animals are able to produce sounds along a continuum from tonal to pulsed [7][8][9]. As we did not have access to the raw data underlying the various published spectrograms, we based our grouping on published spectral features.…”

“…Acoustic recordings from Australia do not exist. Off Hawaii and in the Caribbean, whistles with fundamentals of 890-24,500 Hz and 0.1-1.4-s duration have been recorded [7,228,229]. Burst-pulse sounds appear more broadband (0.5-40 kHz) with 0.1-s duration, 2.47-ms IPI, 47 pulses/train, and a source level of about 165 dB re 1 µPa rms @ 1 m [228,229].…”

Whistle characteristics and daytime dive behavior in pantropical spotted dolphins (Stenella attenuata) in Hawai‘i measured using digital acoustic recording tags (DTAGs)

“…However, until recently, DTAG deployments on small odontocetes have been limited by the comparatively large size of acoustic recording tags and the active behavior of the study animals. This is only the second published study to demonstrate deployment of acoustic tags on a small pelagic delphinid species (see Kaplan et al, 2014). Small pelagic delphinids have some of the highest densities for marine mammals at sea; they often travel in large groups of hundreds of animals (Rankin et al, 2008) and thus anthropogenic activities can expose many individuals (i.e., high numbers of "level B takes" in terms of the U.S. Marine Mammal Protection Act).…”

“…DTAGs have been deployed on multiple cetacean taxa including various baleen, beaked, and pilot whales (reviewed in Johnson et al, 2009). The latest version of the tag, the DTAG3, was developed for attachment to smaller odontocetes and was recently used to study the acoustic repertoire of melonheaded whales (Peponocephala electra; Kaplan et al, 2014). The DTAG3 has yet to be utilized on many species of small odontocetes, despite their relative abundance and the potential influence of noise exposure on large numbers of individuals.…”

Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity

“…Melon-headed whales primarily rest, socialize and travel during the day, and forage at night , Baird 2016). The species is vocally active, producing a variety of whistles and clicks (Frankel & Yin 2010, Kaplan et al 2014. As in other delphinids, clicks are used in echolocation, and whistles are likely important for communication, maintaining group cohesion and facilitating social interactions.…”