Temporal evolution of the Mediterranean fin whale song

Abstract

We present an analysis of fin whale (Balaenoptera physalus) songs on passive acoustic recordings from the Pelagos Sanctuary (Western Mediterranean Basin). The recordings were gathered between 2008 and 2018 using 2 different hydrophone stations. We show how 20 Hz fin whale pulses can be automatically detected using a low complexity convolutional neural network (CNN) despite data variability (different recording devices exposed to diverse noises). The pulses were further classified into the two categories described in past studies and inter pulse intervals (IPI) were measured. The results confirm previous observations on the local relationship between pulse type and IPI with substantially more data. Furthermore we show inter-annual shifts in IPI and an intra-annual trend in pulse center frequency. This study provides new elements of comparison for the understanding of long term fin whale song trends worldwide.

Fin whale singalong: evidence of song conformity

“…After the song transition, we found a gradual increase in song INIs along with a decrease in peak frequencies of the 20-Hz and HF notes. These findings are in line with the gradual trends of decreasing frequencies 27,29,41 and increasing INIs 25,27,30 described for fin whale songs in other ocean basins and in the Mediterranean Sea. Contrarily to the rapid changes in INIs, a global-scale process of cultural transmission cannot explain these directional changes.…”

“…Fin whales produce low-frequency songs that are believed to act as mating displays 17 , because they are produced by males 18 and intensify during the breeding season 17,[19][20][21] . In this species, the song inter-note interval (INI) (i.e., rhythm) is the most distinctive parameter between regions 17,[22][23][24][25] and can change abruptly from one year to the next 22,[24][25][26] or progressively over time [26][27][28][29] . Moreover, frequencies of two fin whale song components, the 20-Hz note and the higher frequency (~130-Hz) upsweep (hereafter HF note) 22 , have been decreasing gradually over the last decade in different ocean basins 27,28 .…”

“…Moreover, frequencies of two fin whale song components, the 20-Hz note and the higher frequency (~130-Hz) upsweep (hereafter HF note) 22 , have been decreasing gradually over the last decade in different ocean basins 27,28 . So far, studies on fin whale song changes have been merely descriptive and only focused on the potential drivers of these variations [24][25][26][27][28][29][30] .…”

Targeting fin whale conservation in the North-Western Mediterranean Sea: insights on movements and behaviour from biologging and habitat modelling

“…In general, both home and core ranges encompass critical habitats for fin whales in the North-Western Mediterranean Sea and agree well with prior knowledge on the presence and behaviour of fin whales in this portion of the Basin. Recent summer wide-scale aerial surveys [78][79][80], as well as studies based on photographic mark recapture [40,81] and visual [82] and acoustic surveys [27,83], 0q 3q E 6 q E 9 q E 1 2 q E 0 q 3q E 6 q E 9 q E 1 2 q E 0q 3q E 0 preferred habitat (% of daily occurrence) (for frequency estimate >1% of total days) 20 40 60 80 100 show a consistent seasonal use of the Balearic Sea, the slope, and offshore waters of the Gulf of Lion and the Corso-Provençal-Ligurian Basin for feeding purposes. In this context, our study demonstrates that animal-borne tracking technology can be used to support and consolidate other approaches.…”

Fin whale song evolution in the North Atlantic

“…These authors concluded that differences in songs may reflect differences in fin whale movements and/or social and vocal behaviours that occur at shorter timescales than genome evolution. In fact, fin whale song INIs can change abruptly from one year to the next in the same region ( Delarue et al, 2009 ; Hatch and Clark, 2004 ; Helble et al, 2020 ; Morano et al, 2012 ; Širović et al, 2017 ) and have been progressively changing over time in different ocean regions ( Best et al, 2022 ; Helble et al, 2020 ; Leroy et al, 2018a ; Weirathmueller et al, 2017 ). Also, the center frequencies of two fin whale song components, the 20 Hz note and the higher frequency (~130 Hz) upsweep (hereafter HF note; Hatch and Clark, 2004 ), have been decreasing gradually over the last decade in different ocean basins ( Leroy et al, 2018a ; Weirathmueller et al, 2017 ; Wood and Širović, 2022 ).…”