Underwater vocal complexity of Arctic sealErignathus barbatusin Kongsfjorden (Svalbard)

Abstract

In this study the description of underwater vocal repertoire of bearded seal in Svalbard (Norway) was extended. Two autonomous passive acoustic recorders were deployed for one year (August 2014-July 2015) in the inner and outer parts of the Kongsfjorden, and 1728 h were recorded and 17 220 vocalizations were found. Nine different vocalization classes were identified and characterized using ten acoustic parameters. The calls showed heterogeneous spectral features, but share the descending trend of frequency modulation. The different classes emerged were discriminated primarily by bandwidth and duration, and then by minimum frequency, central frequency, and maximum frequency in this order. This study represents a step forward to improve the understanding of the acoustic behaviour and the social function of these calls, and identified long passive acoustic monitoring as an effective method to assess vocal complexity and the ecology of marine species producing sounds.

Individual variability in diving, movement and activity patterns of adult bearded seals in Svalbard, Norway

“…This is likely related to the breeding behaviour of some male bearded seals that use a “roaming” strategy 38 , 53 . Male bearded seals in Svalbard vocalize intensively from early April to mid July, with mating taking place after pups are weaned in mid to late May 54 , 55 .…”

Bearded seal (Erignathus barbatus) vocalizations across seasons and habitat types in Svalbard, Norway

“…Spectrograms of each acoustic file (one file for each hour) were generated using the bioacoustics software Ishmael (version 3.0) in order to screen the data records for bearded seal vocalizations FFT 20,148/4096,75% overlap,Hanning window). This study follows the most recent classification of the underwater vocal repertoire of bearded seals in Svalbard, which recognizes nine different vocalization types (Parisi et al 2017). Firstly, bearded seal vocal presence was assessed by scoring every hour in a binary manner for the entire recording period at each location; detections of any of the nine vocalization types were assigned a (1) and an absence of calling was assigned a (0).…”

“…For example, bearded seals vocalize year-round in the Beaufort Sea (MacIntyre et al 2013), whereas they vocalize in a more seasonally restricted fashion in Svalbard, with most calling taking place in the period from February to July (Van Parijs et al 2001;Parisi et al 2017). Some call types, such as moans, a short duration vocalization of low to mid-frequency, seem to be widely used outside the mating season, but use of these shorter calls decreases towards the peak of the mating period (Frouin-Mouy et al 2016;Parisi et al 2017). Trills are the dominant call type during the months that mating occurs (Van Parijs et al 2001;Risch et al 2007;Frouin-Mouy et al 2016;Parisi et al 2017).…”

“…Some call types, such as moans, a short duration vocalization of low to mid-frequency, seem to be widely used outside the mating season, but use of these shorter calls decreases towards the peak of the mating period (Frouin-Mouy et al 2016;Parisi et al 2017). Trills are the dominant call type during the months that mating occurs (Van Parijs et al 2001;Risch et al 2007;Frouin-Mouy et al 2016;Parisi et al 2017). Trills are long duration calls that exhibit frequency modulation and occur across a wide frequency band; they are assumed to advertise the breeding condition of males (Burns 1981;Cleator et al 1989).…”

“…Previous studies of the acoustic behaviour of Svalbard's bearded seals have all been conducted in Kongsfjorden (Fig. 1a, b) (Van Parijs et al 2001, 2003, 2004Parisi et al 2017;de Vincenzi et al 2019). These research efforts have contributed to a better understanding of the vocal biology of this species and provide a baseline for future monitoring efforts.…”