Abstract
Songs are distinct, patterned sounds produced by a variety of animals including baleen whales. Fin whale songs, which consist of short pulses repeated at regular interpulse intervals (IPIs), have been suggested as a tool to distinguish populations. Fin whale songs were analyzed from data collected from 2000–2012 in Southern California and from 2004–2010 in the Gulf of California using autonomous acoustic recorders. IPIs were measured for each identifiable song sequence during two random days of each month with recordings. Four distinct song types were identified: long doublet, short doublet, long triplet, and short triplet. Long and short doublets were the dominant songs in Southern California, while long and short triplets were dominant in the Gulf of California. An abrupt change in song type occurred in both areas during the monitoring period. We argue that each song type is unique to a population and these changes represent a shift in the primary population in the monitoring area. Occasional temporal and spatial song overlap indicated some exchange or visitation among populations. Fin whales appear to synchronize and gradually modify song rhythm over long time scales. A better understanding of the evolutionary and ecological importance of songs to fin whale populations is needed.
Highlights
Songs are distinctive sounds or sequences of sounds produced in a repeated pattern[1]
Four distinct song types were identified in the data and were termed long doublet, short doublet, long triplet, and short triplet based on the total interpulse intervals (IPIs) durations of the song and the patterns of intervals within the series
This monthly pattern of longer IPIs during the winter months and shorter IPIs in the summer months was shown to be the dominant descriptor within the generalized additive modeling (GAM) framework (Table 1)
Summary
Songs are distinctive sounds or sequences of sounds produced in a repeated pattern[1]. The specificity can show itself in the presence of higher frequency pulse components[11, 12], or in the interpulse interval (IPI) durations of a song sequence, with all members in an area seemingly matching the same frequency and IPI features[9, 10, 13] Based on their IPIs, fin whale songs can be classified into three broad categories: singlets, doublets, and triplets[9, 10, 14]. Previous analyses of fin whale acoustic records have generally focused on broad spatial and temporal patterns of call occurrence, or more detailed call descriptions, while grouping all 20 Hz calls into a single category[11, 17, 19,20,21,22,23,24] Based on such analyses, we know fin whales produce 20 Hz calls year-round in Southern California, with a decrease in calling during the summer[17]. A more detailed analysis of calling patterns is needed to reveal those elements
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