Variability and context specificity of narwhal (Monodon monoceros) whistles and pulsed calls

Abstract

The behavioral and environmental context of animal calls provides insights into their functions. Narwhals are a highly vocal species and, like other social cetaceans, rely on acoustic signals to communicate. We characterize and categorize narwhal whistles and pulsed calls, as well as investigate variation in these calls under different contexts (behavior, herd, and year) using recordings made during the month of August 2006–2008, in Koluktoo Bay (72°04′N, 80°32′W). We detected similarities among whistles but not pulsed calls that were produced under a similar behavioral context. Both whistles and pulsed calls recorded within the same herd were more similar than whistles and pulsed calls recorded within different herds. We did not find any type of whistle to be associated with a specific behavior although some acoustical features might be behavior specific. Both whistles and pulsed calls show properties that are consistent with the hypothesis that narwhals produce group‐ or individual‐specific calls.

Highly Directional Sonar Beam of Narwhals (Monodon monoceros) Measured with a Vertical 16 Hydrophone Array

“…Clicks and whistles up to 24 kHz were first described [24, 25], with Watkins et al [24] acknowledging that they did not cover the full repertoire of narwhal. More recent studies using single receivers resulted in the description of whistles, pulsed calls, and clicks [26, 27]. Recordings with higher sampling rates revealed the true broadband nature of narwhal clicks where train clicks contained energy at above 100 kHz [28] and even extending above 200 kHz [29].…”

Seasonal Trends in Acoustic Detection of Marine Mammals in Baffin Bay and Melville Bay, Northwest Greenland + Supplementary Appendix 1 (See Article Tools)

“…Mysticete calls are commonly detected at ranges of several tens of kilometres on a single hydrophone , while odontocete clicks and whistles can be detected at ranges of 1 -6 km (Quintana-Rizzo et al, 2006;Wang et al, 2006;Jensen et al, 2012;Ainslie, 2013). Stafford et al (2012a) and Marcoux et al (2012) discuss the large overlap in vocal repertoires of the two Monodontid species (beluga whales and narwhals) that share migration routes in Baffin Bay (Heide-Jørgensen et al, 2003a, c). To our knowledge, no studies have systematically discriminated between calls of these species.…”

A multi-year study of narwhal occurrence in the western Fram Strait—detected via passive acoustic monitoring

“…Since narwhal pulsed and tonal signals (used for communication) and echolocation clicks (used for navigation and locating prey) are produced year-round (Marcoux, Auger-Méthé & Humphries 2011;Stafford, Laidre et al 2012), it is reasonable to postulate that the observed acoustic presence is a good proxy for overall occurrence of this species in the area. Furthermore, a recent study of narwhals tagged with short-term acoustic devices in coastal areas of East Greenland showed that narwhal pulsed and tonal signals were recorded most often when the animals were at depths of less than 100 m (Blackwell et al 2018), that is, within the same depth range as the hydrophone in the current study (75 m).…”

“…If visual inspection did not provide an unambiguous "yes/no" for acoustic presence, the corresponding sound files were listened to in order to classify the sounds correctly. Narwhals and white whales produce sounds within overlapping frequency ranges and therefore distinguishing between these two can be difficult if both species are present in acoustic recordings (Marcoux, Auger-Méthé & Humphries 2011;Stafford, Laidre et al 2012;Frouin-Mouy et al 2017). However, white whales are not known to occur in this area.…”