Sascha K. Hooker and Hal Whitehead. In press.
Marine Mammal Science.
Sounds produced by northern bottlenose whales (Hyperoodon ampullatus) recorded
in the Gully, a submarine canyon off Nova Scotia, consisted predominately of clicks.
In 428 minutes of recordings no whistles were heard which could unequivocally be
attributed to bottlenose whales. There were two major types of click series, initially
distinguished by large differences in received amplitude. Loud clicks (produced by nearby
whales socializing at the surface) were rapid, with short and variable inter-click
intervals (mean 0.07 s; CV 71%). The frequency spectra of these were variable and often
multimodal, with peak frequencies ranging between 2 and 22 kHz (mean 11 kHz, CV 59%).
Clicks received at low amplitude (produced by distant whales, presumably foraging
at depth) had more consistent inter-click intervals (mean 0.40 s, CV 12.5%), generally
unimodal frequency spectra with a mean peak frequency of 24 kHz (CV 7%) and 3 dB
bandwidth of 4 kHz. Echolocation inter-click intervals may reflect the approximate
search distance of an animal, in this case 300 m, comparable to that found for sperm
whales. The relationship between click frequency and the size of object being
investigated, suggests that 24 kHz would be optimal for an object of approximately
6 cm or more, consistent with the size range of their squid prey.