Sounds recorded in the presence of Blainville’s beaked whales, Mesoplodon densirostris, near Hawai’i

Abstract

During a combined visual and acoustic cetacean survey of the Hawaiian Islands in 2002, four midfrequency sounds were recorded in close proximity to a group of Blainville's beaked whales, Mesoplodon densirostris. These sounds included one frequency-modulated whistle, and three frequency- and amplitude-modulated pulsed sounds, with energy between 6 and 16 kHz. Until recently, little was known of the acoustic behavior of beaked whales, and early descriptions of audible sounds made by beaked whales are incomplete [Caldwell and Caldwell, Cetology 4, 1-5 (1971); Lynn and Reiss, Marine Mammal Sci. 8(3), 229-305 (1992); T. C. Poulter, "Marine mammals," in Animal Communication; Techniques of Study and Results of Research, edited by T. A. Sebeok (Indiana University Press, Bloomington, 1968)]. Recent recordings of high-frequency clicks (>20 kHz, [Johnson et al., Proc. R. Soc. London, Ser. B (Suppl.) 271, 5383-5386 (2004); Zimmer et al., J. Acoust. Soc. Am. 117(6), 3919-3927.]) were above the frequency response of our equipment, and therefore not detected. Sound production within the midfrequency range of sounds described here suggests that the hearing of M. densirostris is sensitive at frequencies used in some types of active sonars.