Changes in fin whale (Balaenoptera physalus) song over a forty-four year period in New England waters

Although much marine mammal research has been conducted on whales in the waters surrounding Cape Cod, Massachusetts, little work has been done on the supposed resident fin whale (Balaenoptera physalus) population that resides in this area. Fin whales have three different sounds in their vocal repertoire but a relatively simple song that is composed of long trains of high intensity 20-Hz pulses. Performed only by males, the song may be a reproductive display with song characteristics evolutionarily fixed within populations. In this study, fin whale vocalizations recorded in the area of Cape Cod Bay during the years 1961, 1978, 2001, and 2005 were characterized and compared within years to detect possible divergence in the male song. Reliable comparisons with the earlier data proved difficult because of small sample sizes under the chosen song parameters. However, measurements of inter-pulse interval and song length did vary significantly between the short time span of 2001 to 2005. Mean inter-pulse intervals were shorter in 2001, and song duration was longer within the 2005 recordings. Negative correlations between the center frequency and the song duration, as well as the center frequency and inter-pulse interval were also found. Although we rejected the null hypothesis that song notes and features are fixed and do not change over time, we did discover valuable information regarding the relationships between different features of fin whale song. Based on comparison of the temporal and individual variation observed in our data with those collected on a population in Bermuda, it is unclear whether vocal characteristics are distinct and could be an identifying feature of separate breeding populations