The monopulsed nature of sperm whale clicks
30 Jul 2003-Journal of the Acoustical Society of America (Acoustical Society of America)-Vol. 114, Iss: 2, pp 1143-1154
TL;DR: On-axis click properties support previous work proposing the nose of sperm whales to operate as a generator of sound.
Abstract: Traditionally, sperm whale clicks have been described as multipulsed, long duration, nondirectional signals of moderate intensity and with a spectrum peaking below 10 kHz. Such properties are counterindicative of a sonar function, and quite different from the properties of dolphin sonar clicks. Here, data are presented suggesting that the traditional view of sperm whale clicks is incomplete and derived from off-axis recordings of a highly directional source. A limited number of assumed on-axis clicks were recorded and found to be essentially monopulsed clicks, with durations of 100 micros, with a composite directionality index of 27 dB, with source levels up to 236 dB re: 1 microPa (rms), and with centroid frequencies of 15 kHz. Such clicks meet the requirements for long-range biosonar purposes. Data were obtained with a large-aperture, GPS-synchronized array in July 2000 in the Bleik Canyon off Vesteralen, Norway (69 degrees 28' N, 15 degrees 40' E). A total of 14 h of sound recordings was collected from five to ten independent, simultaneously operating recording units. The sound levels measured make sperm whale clicks by far the loudest of sounds recorded from any biological source. On-axis click properties support previous work proposing the nose of sperm whales to operate as a generator of sound.
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TL;DR: Beaked whales (Cetacea: Ziphiidea) of the genera Ziphius and Mesoplodon are so difficult to study that they are mostly known from strandings.
Abstract: Beaked whales (Cetacea: Ziphiidea) of the genera Ziphius and Mesoplodon are so difficult to study that they are mostly known from strandings. How these elusive toothed whales use and react to sound...
379 citations
TL;DR: Similarity in foraging behaviour in the three regions and high diving efficiencies suggest that the success of sperm whales as mesopelagic predators is due in part to long-range echolocation of deep prey patches, efficient locomotion and a large aerobic capacity during diving.
Abstract: 1. Digital tags were used to describe diving and vocal behaviour of sperm whales during 198 complete and partial foraging dives made by 37 individual sperm whales in the Atlantic Ocean, the Gulf of Mexico and the Ligurian Sea. 2. The maximum depth of dive averaged by individual differed across the three regions and was 985 m (SD = 124.3), 644 m (123.4) and 827 m (60.3), respectively. An average dive cycle consisted of a 45 min (6.3) dive with a 9 min (3.0) surface interval, with no significant differences among regions. On average, whales spent greater than 72% of their time in foraging dive cycles. 3. Whales produced regular clicks for 81% (4.1) of a dive and 64% (14.6) of the descent phase. The occurrence of buzz vocalizations (also called 'creaks') as an indicator of the foraging phase of a dive showed no difference in mean prey capture attempts per dive between regions [18 buzzes/dive (7.6)]. Sperm whales descended a mean of 392 m (144) from the start of regular clicking to the first buzz, which supports the hypothesis that regular clicks function as a long-range biosonar. 4. There were no significant differences in the duration of the foraging phase [28 min (6.0)] or percentage of the dive duration in the foraging phase [62% (7.3)] between the three regions, with an overall average proportion of time spent actively encountering prey during dive cycles of 0.53 (0.05). Whales maintained their time in the foraging phase by decreasing transit time for deeper foraging dives. 5. Similarity in foraging behaviour in the three regions and high diving efficiencies suggest that the success of sperm whales as mesopelagic predators is due in part to long-range echolocation of deep prey patches, efficient locomotion and a large aerobic capacity during diving.
364 citations
Cites background from "The monopulsed nature of sperm whal..."
...Whales began clicking at an average range of 295–539 m from the depth of the first recorded buzz, which is well within the theoretical range over which sperm whales should be able to detect squid based on the properties of their regular clicks (Møhl et al. 2003)....
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...Whales began clicking at an average range of 295–539 m from the depth of the first recorded buzz, which is well within the theoretical range over which sperm whales should be able to detect squid based on the properties of their regular clicks (Møhl et al. 2003)....
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TL;DR: The hypothesis that creaks are an echolocation signal adapted for foraging, analogous to terminal buzzes in taxonomically diverse echlocating species, strongly support the hypothesis thatcreaks are produced during prey capture.
Abstract: During foraging dives, sperm whales (Physeter macrocephalus) produce long series of regular clicks at 0.5-2 s intervals interspersed with rapid-click buzzes called "creaks". Sound, depth and orientation recording Dtags were attached to 23 whales in the Ligurian Sea and Gulf of Mexico to test whether the behaviour of diving sperm whales supports the hypothesis that creaks are produced during prey capture. Sperm whales spent most of their bottom time within one or two depth bands, apparently feeding in vertically stratified prey layers. Creak rates were highest during the bottom phase: 99.8% of creaks were produced in the deepest 50% of dives, 57% in the deepest 15% of dives. Whales swam actively during the bottom phase, producing a mean of 12.5 depth inflections per dive. A mean of 32% of creaks produced during the bottom phase occurred within 10 s of an inflection (13x more than chance). Sperm whales actively altered their body orientation throughout the bottom phase with significantly increased rates of change during creaks, reflecting increased manoeuvring. Sperm whales increased their bottom foraging time when creak rates were higher. These results all strongly support the hypothesis that creaks are an echolocation signal adapted for foraging, analogous to terminal buzzes in taxonomically diverse echolocating species.
262 citations
Cites background from "The monopulsed nature of sperm whal..."
...Source levels within the beam are estimated to be as high as 236dB re 1lPa at 1 m. (Møhl et al. 2003)....
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TL;DR: Qu quantitative characteristics of clicks from deep-diving Cuvier's beaked whales (Ziphius cavirostris) are reported using a unique data set and the potential for passive detection is enhanced.
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 cavirostris) 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 (±0.09) and 0.40 s (±0.07). The clicks are frequency modulated pulses with durations of ∼200 μs and center frequencies around 42 kHz, −10 dB bandwidths of 22 kHz, and Q3 dB of 4. The sound beam is narrow with an estimated directionality index of more than 25 dB...
241 citations
TL;DR: Blainville's beaked whales (Mesoplodon densirostris Blainville) echolocate for prey during deep foraging dives using acoustic tags to demonstrate that these whales produce two distinct types of click sounds during different phases in biosonar-based foraging.
Abstract: SUMMARY Blainville9s beaked whales ( Mesoplodon densirostris Blainville)
echolocate for prey during deep foraging dives. Here we use acoustic tags to
demonstrate that these whales, in contrast to other toothed whales studied,
produce two distinct types of click sounds during different phases in
biosonar-based foraging. Search clicks are emitted during foraging dives with
inter-click intervals typically between 0.2 and 0.4 s. They have the
distinctive form of an FM upsweep (modulation rate of about 110 kHz
ms -1 ) with a -10 dB bandwidth from 26 to 51 kHz and a pulse length
of 270 μs, somewhat similar to chirp signals in bats and Cuvier9s beaked
whales ( Ziphius cavirostris Cuvier), but quite different from clicks
of other toothed whales studied. In comparison, the buzz clicks, produced in
short bursts during the final stage of prey capture, are short (105 μs)
transients with no FM structure and a -10 dB bandwidth from 25 to 80 kHz or
higher. Buzz clicks have properties similar to clicks reported from large
delphinids and hold the potential for higher temporal resolution than the FM
clicks. It is suggested that the two click types are adapted to the separate
problems of target detection and classification versus capture of low
target strength prey in a cluttered acoustic environment.
229 citations
Cites background from "The monopulsed nature of sperm whal..."
...On this presumption, the click with maximum amplitude in each sequence will be the closest to representing an on-axis version of the click (Møhl et al., 2003)....
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...The low-frequency, multi-pulsed clicks of sperm whales form a third category (Møhl et al., 2003)....
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References
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TL;DR: Comparing and contrasting the morphologic patterns of nasal structures across species representing every extant odontocete superfamily reveals probable homologous relationships, which suggests that all toothed whales may be making their biosonar signals by a similar mechanism.
Abstract: The site and physiologic mechanism(s) responsible for the generation of odontocete biosonar signals have eluded investigators for decades. To address these issues we subjected postmortem toothed whale heads to interrogation using medical imaging techniques. Most of the 40 specimens (from 19 species) were examined using x-ray computed tomography (CT) and/or magnetic resonance imaging (MR). Interpretation of scan images was aided by subsequent dissection of the specimens or, in one case, by cryosectioning. In all specimens we described a similar tissue complex and identified it as the hypothetical biosonar signal generator. This complex includes a small pair of fatty bursae embedded in a pair of connective tissue lips, a cartilaginous blade, a stout ligament, and an array of soft tissue air sacs. Comparing and contrasting the morphologic patterns of nasal structures across species representing every extant odontocete superfamily reveals probable homologous relationships, which suggests that all toothed whales may be making their biosonar signals by a similar mechanism.
437 citations
TL;DR: Previously published properties of sperm whale clicks underestimate the capabilities of the sound generator and therefore cannot falsify the Norris and Harvey theory.
Abstract: In sperm whales (Physeter catodon L. 1758) the nose is vastly hypertrophied, accounting for about one-third of the length or weight of an adult male. Norris and Harvey [in Animal Orientation and Navigation, NASA SP-262 (1972), pp. 397–417] ascribed a sound-generating function to this organ complex. A sound generator weighing upward of 10 tons and with a cross-section of 1 m is expected to generate high-intensity, directional sounds. This prediction from the Norris and Harvey theory is not supported by published data for sperm whale clicks (source levels of 180 dB re 1 μPa and little, if any, directionality). Either the theory is not borne out or the data is not representative for the capabilities of the sound-generating mechanism. To increase the amount of relevant data, a five-hydrophone array, suspended from three platforms separated by 1 km and linked by radio, was deployed at the slope of the continental shelf off Andenes, Norway, in the summers of 1997 and 1998. With this system, source levels up to 223 dB re 1 μPa peRMS were recorded. Also, source level differences of 35 dB for the same click at different directions were seen, which are interpreted as evidence for high directionality. This implicates sonar as a possible function of the clicks. Thus, previously published properties of sperm whale clicks underestimate the capabilities of the sound generator and therefore cannot falsify the Norris and Harvey theory.
220 citations
TL;DR: Shared click features suggest that sound production in sperm whales is based on the same fundamental biomechanics as in smaller odontocetes and that the nasal complexes are therefore not only anatomically but also functionally homologous in generating the initial sound pulse.
Abstract: Delphinoids (Delphinidae, Odontoceti) produce tonal sounds and clicks by forcing pressurized air past phonic lips in the nasal complex. It has been proposed that homologous, hypertrophied nasal structures in the deep-diving sperm whale (Physeter macrocephalus) (Physeteridae, Odontoceti) are dedicated to the production of clicks. However, air volumes in diving mammals are reduced with increasing ambient pressure, which seems likely to influence pneumatic sound production at depth. To study sperm whale sound production at depth, we attached ultrasound time/depth-recording tags to sperm whales by means of a pole and suction cup. We demonstrate that sperm whale click production in terms of output and frequency content is unaffected by hydrostatic reduction in available air volume down to less than 2 % of the initial air volume in the nasal complex. We present evidence suggesting that the sound-generating mechanism has a bimodal function, allowing for the production of clicks suited for biosonar and clicks more suited for communication. Shared click features suggest that sound production in sperm whales is based on the same fundamental biomechanics as in smaller odontocetes and that the nasal complexes are therefore not only anatomically but also functionally homologous in generating the initial sound pulse.
214 citations
"The monopulsed nature of sperm whal..." refers background in this paper
...Here, data are presented suggesting that the traditional view of sperm whale clicks is incomplete and derived from off-axis recordings of a highly directional source....
[...]
TL;DR: The echlocation signals of two Atlantic bottlenose dolphins were measured while the animals were involved in a target‐detection experiment conducted in open waters, and the time intervals between successive pulses in a pulse train were found to be highly variable.
Abstract: The echlocation signals of two Atlantic bottlenose dolphins, Tursiops truncatus, were measured while the animals were involved in a target‐detection experiment conducted in open waters. The time intervals between successive pulses in a pulse train were found to be highly variable, although the intervals were longer than the time needed for an acoustic signal to travel from the animals to the target and back. Sound pressure levels of the echoranging signals were measured for target ranges of 60, 70, 75, and 80 yds. The peak‐to‐peak click‐source level at 1 yd showed little variation with the target range; the average level was 120.4 dB re 1 μbar for one animal and 122.3 dB for the other. These open‐water sound pressure levels are at least 30 dB higher than any click‐source levels reported in the literature. Oscilloscope photographs and their Fourier transforms of these high‐amplitude clicks are presented. The typical clicks had average durations of 40 μsec, with peak energies between 120 and 130 kHz, much higher than the previously reported energy peaks centered at 35 to 60 kHz.
206 citations
TL;DR: It is concluded that echolocation is an important sensory cue in prey location and sperm whales producing slow clicks may represent an odontocete species that utilizes long-range sound communication.
Abstract: Sperm whales (Physeter macrocephalus) are deep-diving predators foraging in meso- and bathypelagic ecosystems off the continental shelves. To investigate the ecophysiological and communicative function of various click types from male sperm whales in a high-latitude habitat, we deployed a large-aperture array of calibrated hydrophones off northern Norway (N69, E15). Data show that sperm whales in this habitat produce three click types: usual clicks, creak clicks and, occasionally, slow clicks. Usual clicks and creak clicks exhibit short duration, profound directionality and a frequency content suited for echolocation on meso- and bathypelagic fish and squids. The acoustic properties and low repetition rate of usual clicks are suited for long-range echolocation, whereas creak clicks have properties equivalent to signals in buzzes, the terminating pulse trains known from echolocating bats during prey capture. From these source parameters and the high acoustic activity during foraging dives, it is concluded that echolocation is an important sensory cue in prey location. Sound pressure levels of creak clicks and usual clicks measured off the acoustic axis suggest that sperm whales may be subjected to eavesdropping by conspecifics, thereby conveying information about food aggregations at estimated ranges of 6 km for creak clicks and 16 km for usual clicks. Slow clicks exhibit low directionality, low-frequency emphasis and a reduced repetition rate, suggesting that this click type is more suited for communication than for echolocation. Slow clicks can be detected by submerged conspecifics at ranges up to 60 km. Thus, sperm whales producing slow clicks may represent an odontocete species that utilizes long-range sound communication.
182 citations