Echolocation clicks of free-ranging Cuvier’s beaked whales (Ziphius cavirostris)

Abstract

Strandings of beaked whales of the genera Ziphius and Mesoplodon have been reported to occur in conjunction with naval sonar use. Detection of the sounds from these elusive whales could reduce the risk of exposure, but descriptions of their vocalizations are at best incomplete. This paper reports quantitative characteristics of clicks from deep-diving Cuvier's beaked whales ͑Ziphius cavirostris͒ using a unique data set. Two whales in the Ligurian Sea were simultaneously tagged with sound and orientation recording tags, and the dive tracks were reconstructed allowing for derivation of the range and relative aspect between the clicking whales. At depth, the whales produced trains of regular echolocation clicks with mean interclick intervals of 0.43 s (Ϯ0.09) and 0.40 s (Ϯ0.07). The clicks are frequency modulated pulses with durations of ϳ200 s and center frequencies around 42 kHz, Ϫ10 dB bandwidths of 22 kHz, and Q 3 dB of 4. The sound beam is narrow with an estimated directionality index of more than 25 dB, source levels up to 214 dB pp re: 1 Pa at 1 m, and energy flux density of 164 dB re: 1 Pa 2 s. As the spectral and temporal properties are different from those of nonziphiid odontocetes the potential for passive detection is enhanced.

Effective beam pattern of the Blainville's beaked whale (Mesoplodon densirostris) and implications for passive acoustic monitoring

“…Much of what is known about the foraging behavior and sound production of this species has come from sound and movement recording tags attached to the dorsal surface of animals Madsen et al, 2005;Zimmer et al, 2005). Similar data have also been obtained from Cuvier's beaked whale (Ziphius cavirostris), another species considered to be sensitive to sonar (D'Amico et al, 2009).…”

“…However, the improved localization accuracy highlights several other sources of error that must be considered both in estimating the transmission beam pattern and in modeling PAM performance. Even with the body orientation known precisely from a tag, the orientation of the head, and therefore the sound source, may differ from the body orientation as the animal moves its head independently of body motions while echolocating (Rasmussen et al, 2004;Zimmer et al, 2005). This leads to an apparent widening of the beam pattern when averaged over multiple clicks that may increase the probability of detection of a PAM system.…”

“…Following Zimmer et al (2005), we assume that the sound source has a fixed but unknown orientation with respect to the whale's body axes. This assumption breaks down if the whale turns its head without turning the body, an action which may occur often during foraging.…”

Clicking for calamari: toothed whales can echolocate squid Loligo pealeii

“…5). While beaked whales and large delphinids produce clicks with comparable energy flux source levels , Zimmer et al 2005, Au et al 2007), they may hunt in quite different ambient noise environments. Thus, we consider the detection performance of a beaked whale in a low-noise deep ocean environment (Au et al 2002) and that of a Au et al 2007) of 3 different targets with TS E of -41, -61 and -70 dB by 3 different toothed whale species: (A) a sperm whale with a sonar click source level of 190 dB re 1 μPa 2 s, and (B) a beaked whale and (C) a delphinid with sonar click source levels of 167 dB re 1 μPa 2 s. The estimated detection ranges for the beaked whale will also be applicable for the delphinid under low noise conditions and the estimated ranges for the delphinid will be applicable for the beaked whale under high noise conditions.…”

“…2a,b). The second simulated the frequency-modulated click of a mediumsized beaked whale (Zimmer et al 2005, with a duration of around 210 μs, a centroid frequency of 51 kHz and a -10 dB BW of 24 kHz (Fig. 2c,d).…”