Spermaceti Organ Research Articles

Consistent acoustic size estimation of sperm whales using clicks recorded from unknown aspects

The multipulse structure of sperm whale clicks offers a unique way to acoustically estimate body length, as the inter-pulse intervals within the clicks relate to the two-way travel time within and thereby to the size of the hypertrophied nose in this species. Despite its large potential to allow the estimation of length acoustically, the technique has only been used in a few studies to assess the length composition of sperm whale populations. Its limited use may relate to the fact that only some clicks within a click series normally display the regular multipulsed structure required for size estimation. The inter-pulse intervals of usual clicks vary with the recording aspect to the clicking whale and the pulse delays are not necessarily directly related to the length of the spermaceti organ. To overcome these difficulties, a method is provided to estimate sperm whale body lengths, based on averages of cepstra derived from a large number of clicks recorded from whales in unknown recording aspects. This study shows that the two-way travel time in the spermaceti organ can consistently be estimated by a peak in the averaged cepstra when a large number of clicks are analysed. This method is shown to give a consistent estimation of the size of the spermaceti organ when recording the whale in an unknown orientation and also when recordings are heavily influenced by surface reflections.

Diaphorocetus poucheti (Cetacea, Odontoceti, Physeteroidea) from Patagonia, Argentina: one of the earliest sperm whales

Sperm whales (Physeteroidea) are the basal-most surviving lineage of odontocetes, represented today by just three highly specialized, deep-diving suction feeders. By contrast, extinct sperm whales were relatively diverse, reflecting a major Miocene diversification into various suction feeding and macroraptorial forms. The beginnings of this diversification, however, remain poorly understood. The Atlantic coast of South America provides a crucial window into early physeteroid evolution and has yielded some of the oldest species known from cranial material, Idiorophus patagonicus and Diaphorocetus poucheti – both of which are in need of re-description and phylogenetic reappraisal. Here, we re-examine Diaphorocetus in detail and, in light of its complex taxonomic history, declare it a nomen protectum. Phylogenetically, the species forms part of a polytomy including ‘Aulophyseter’ rionegresis and the two crown lineages (Physeteridae and Kogiidae) and demonstrates that facial asymmetry and a clearly defined supracranial basin have characterized this lineage for at least 20 Ma. With a total body length of 3.5–4 m, Diaphorocetus is one of the smallest physeteroids yet known. Its cranial morphology hints at an intermediate raptorial/suction feeding strategy and it has a moderately developed spermaceti organ and junk.

Automatic acoustic estimation of sperm whale size distributions achieved through machine recognition of on-axis clicks.

The waveforms of individual sperm whale clicks often appear as multiple pulses, which are the product of a single pulse reverberating throughout the spermaceti organ. Since there is a relationship between spermaceti organ size and total body size, it is possible to estimate a whale's length by measuring the inter-pulse intervals (IPIs) within its clicks. However, if a click is recorded off-axis, the IPI corresponding to spermaceti organ length is usually obscured. This paper presents an algorithm for automatically estimating the "true" IPIs of sperm whales in a recording by measuring them from on-axis clicks only. The routine works by classifying detected clicks with a support vector machine, assessing the stability of their IPIs, and then clustering the stable IPIs using Gaussian mixture models. Results show that the routine is very accurate in obtaining reliable IPIs, but has a high false negative rate. Nonetheless, since sperm whales click very frequently, it is possible to obtain useful IPI distributions with only a few minutes of recording. This algorithm makes it possible to estimate the body lengths of multiple sperm whales automatically with only one hydrophone. An implementation is available for download at http://whitelab.biology.dal.ca/CABLE/cable.htm.

Sperm whale inter-pulse intervals and size: The anomaly called Yukusam

Yukusam is the name given to a male sperm whale who was first documented off northeastern Vancouver Island in February 2018. He spent several weeks in this area before traveling south to the inland waters of the Salish Sea in late March 2018. Sperm whale clicks have been used as a proxy to determine overall size by using the time difference of arrival between the initial noise pulse and its reflections within the spermaceti organ. Different equations have been derived in order to use this Inter-Pulse Interval (IPI) to estimate overall length. Here we use Yukusam’s usual clicks recorded from the Lime Kiln hydrophone on the west side of San Juan Island (WA State, USA) to compare IPI-based length estimates with visual observations. Photo and video documentation indicate that this whale is ~15 m in length. Our initial acoustic results indicate that equations in the literature underestimate his length by at least a few meters. The potential reasons behind these anomalies are explored in this presentation.

Architecture of the sperm whale forehead facilitates ramming combat.

Herman Melville’s novel Moby Dick was inspired by historical instances in which large sperm whales (Physeter macrocephalus L.) sank 19th century whaling ships by ramming them with their foreheads. The immense forehead of sperm whales is possibly the largest, and one of the strangest, anatomical structures in the animal kingdom. It contains two large oil-filled compartments, known as the “spermaceti organ” and “junk,” that constitute up to one-quarter of body mass and extend one-third of the total length of the whale. Recognized as playing an important role in echolocation, previous studies have also attributed the complex structural configuration of the spermaceti organ and junk to acoustic sexual selection, acoustic prey debilitation, buoyancy control, and aggressive ramming. Of these additional suggested functions, ramming remains the most controversial, and the potential mechanical roles of the structural components of the spermaceti organ and junk in ramming remain untested. Here we explore the aggressive ramming hypothesis using a novel combination of structural engineering principles and probabilistic simulation to determine if the unique structure of the junk significantly reduces stress in the skull during quasi-static impact. Our analyses indicate that the connective tissue partitions in the junk reduce von Mises stresses across the skull and that the load-redistribution functionality of the former is insensitive to moderate variation in tissue material parameters, the thickness of the partitions, and variations in the location and angle of the applied load. Absence of the connective tissue partitions increases skull stresses, particularly in the rostral aspect of the upper jaw, further hinting of the important role the architecture of the junk may play in ramming events. Our study also found that impact loads on the spermaceti organ generate lower skull stresses than an impact on the junk. Nevertheless, whilst an impact on the spermaceti organ would reduce skull stresses, it would also cause high compressive stresses on the anterior aspect of the organ and the connective tissue case, possibly making these structures more prone to failure. This outcome, coupled with the facts that the spermaceti organ houses sensitive and essential sonar producing structures and the rostral portion of junk, rather than the spermaceti organ, is frequently a site of significant scarring in mature males suggest that whales avoid impact with the spermaceti organ. Although the unique structure of the junk certainly serves multiple functions, our results are consistent with the hypothesis that the structure also evolved to function as a massive battering ram during male-male competition.

Properties and architecture of the sperm whale skull amphitheatre

The sperm whale skull amphitheatre cradles an enormous two-tonne spermaceti organ. The amphitheatre separates this organ from the cranium and the cervical vertebrae that lie in close proximity to the base of the skull. Here, we elucidate that this skull amphitheatre is an elastic, flexible, triple-layered structure with mechanical properties that are conjointly guided by bone histology and the characteristics of pore space. We contend that the amphitheatre will flex elastically to equilibrate forces transmitted via the spermaceti organ that arise through diving. We find that collisions from sperm whale aggression do not cause the amphitheatre to bend, but rather localise stress to the base of the amphitheatre on its anterior face. We consider, therefore, that the uniquely thin and extended construction of the amphitheatre, has relevance as an energy absorptive structure in diving.

Acoustic property reconstruction of a pygmy sperm whale (Kogia breviceps) forehead based on computed tomography imaging.

Computed tomography (CT) imaging and sound experimental measurements were used to reconstruct the acoustic properties (density, velocity, and impedance) of the forehead tissues of a deceased pygmy sperm whale (Kogia breviceps). The forehead was segmented along the body axis and sectioned into cross section slices, which were further cut into sample pieces for measurements. Hounsfield units (HUs) of the corresponding measured pieces were obtained from CT scans, and regression analyses were conducted to investigate the linear relationships between the tissues' HUs and velocity, and HUs and density. The distributions of the acoustic properties of the head at axial, coronal, and sagittal cross sections were reconstructed, revealing that the nasal passage system was asymmetric and the cornucopia-shaped spermaceti organ was in the right nasal passage, surrounded by tissues and airsacs. A distinct dense theca was discovered in the posterior-dorsal area of the melon, which was characterized by low velocity in the inner core and high velocity in the outer region. Statistical analyses revealed significant differences in density, velocity, and acoustic impedance between all four structures, melon, spermaceti organ, muscle, and connective tissue (p < 0.001). The obtained acoustic properties of the forehead tissues provide important information for understanding the species' bioacoustic characteristics.

Morphology of the Nasal Apparatus in Pygmy (Kogia Breviceps) and Dwarf (K. Sima) Sperm Whales.

Odontocete echolocation clicks are generated by pneumatically driven phonic lips within the nasal passage, and propagated through specialized structures within the forehead. This study investigated the highly derived echolocation structures of the pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales through careful dissections (N = 18 K. breviceps, 6 K. sima) and histological examinations (N = 5 K. breviceps). This study is the first to show that the entire kogiid sound production and transmission pathway is acted upon by complex facial muscles (likely derivations of the m. maxillonasolabialis). Muscles appear capable of tensing and separating the solitary pair of phonic lips, which would control echolocation click frequencies. The phonic lips are enveloped by the "vocal cap," a morphologically complex, connective tissue structure unique to kogiids. Extensive facial muscles appear to control the position of this structure and its spatial relationship to the phonic lips. The vocal cap's numerous air crypts suggest that it may reflect sounds. Muscles encircling the connective tissue case that surrounds the spermaceti organ may change its shape and/or internal pressure. These actions may influence the acoustic energy transmitted from the phonic lips, through this lipid body, to the melon. Facial and rostral muscles act upon the length of the melon, suggesting that the sound "beam" can be focused as it travels through the melon and into the environment. This study suggests that the kogiid echolocation system is highly tunable. Future acoustic studies are required to test these hypotheses and gain further insight into the kogiid echolocation system.

Evolutionary Patterns among Living and Fossil Kogiid Sperm Whales: Evidence from the Neogene of Central America.

Kogiids are known by two living species, the pygmy and dwarf sperm whale (Kogia breviceps and K. sima). Both are relatively rare, and as their names suggest, they are closely related to the sperm whale, all being characterized by the presence of a spermaceti organ. However, this organ is much reduced in kogiids and may have become functionally different. Here we describe a fossil kogiid from the late Miocene of Panama and we explore the evolutionary history of the group with special attention to this evolutionary reduction. The fossil consists of cranial material from the late Tortonian (~7.5 Ma) Piña facies of the Chagres Formation in Panama. Detailed comparison with other fossil and extant kogiids and the results of a phylogenetic analysis place the Panamanian kogiid, herein named Nanokogia isthmia gen. et sp. nov., as a taxon most closely related to Praekogia cedrosensis from the Messinian (~6 Ma) of Baja California and to Kogia spp. Furthermore our results show that reduction of the spermaceti organ has occurred iteratively in kogiids, once in Thalassocetus antwerpiensis in the early-middle Miocene, and more recently in Kogia spp. Additionally, we estimate the divergence between extant species of Kogia at around the late Pliocene, later than previously predicted by molecular estimates. Finally, comparison of Nanokogia with the coeval Scaphokogia cochlearis from Peru shows that these two species display a greater morphological disparity between them than that observed between the extant members of the group. We hypothesize that this reflects differences in feeding ecologies of the two species, with Nanokogia being more similar to extant Kogia. Nanokogia shows that kogiids have been part of the Neotropical marine mammal communities at least since the late Miocene, and gives us insight into the evolutionary history and origins of one of the rarest groups of living whales.

Notes on the brain and encephalization quotient of two sperm whales with a synthesis of the literature and indications of a new method of extraction

The sperm whale (&lt;em&gt;Physeter&lt;/em&gt; &lt;em&gt;macrocephalus&lt;/em&gt;, Linnaeus 1758) possesses the largest brain that ever existed. Relatively few authors have dealt with it and the available descriptions are heterogeneous, with only few data about brain weight or gross anatomy. In fact the central nervous system of large cetaceans is quite difficult to obtain, given the huge body size and the low frequency of strandings of recently dead individuals. Furthermore, since the skull of the sperm whale underwent an extreme transformation for the accommodation of the spermaceti organ, the cranial cavity is surrounded by thick layers of bone and thus difficult to reach under field conditions. We recently had the chance to extract the brain from two stranded sperm whales whose bodies were in good condition. In the present note we describe the main macroscopic characteristics of the sperm whale brain, including its weight and Encephalization Quotient, review the available literature, and describe a possible new approach to the removal and preservation of the organ under field conditions.

An acoustic valve within the nose of sperm whalesPhyseter macrocephalus

Sperm whales Physeter macrocephalus emit impulsive sound signals in short series of rhythmic clicks (codas) for communication, and in long series of single acoustic events (usual clicks) for echolocation. Both click types are generated pneumatically within the hypertrophied nasal complex, at the ‘monkey lips’ at the rostral end of the right nasal passage. Each individual click comprises repetitive pulses decaying in intensity. However, the decay rate is distinctly higher in usual clicks than in coda clicks. The mechanism of decay rate control in the clicks is still unclear, and it is unclear why the right nasal passage crosses the nasal acoustic pathway between two hypertrophied acoustic fat bodies (spermaceti organ, junk), so that it resembles a ‘bent acoustic horn’. We present a new concept to explain how the flat right nasal passage can serve as a variable acoustic valve, and how the amount and distribution of its air filling can be controlled by muscle action. This mechanism allows the whale to determine the pulse decay rate and thus switch between the two modes of click production. Coda clicks are generated by reverberations within the spermaceti organ (partial trapping of sound) and by the release of sound energy in fractions through the air-filled right nasal passage. In contrast, echolocation clicks as single events are released during the partial collapse of the right nasal passage between the spermaceti organ and the junk. This interpretation of the right nasal passage as an adaptive acoustic valve elucidates why the spermaceti organ and the junk are separated from each other by an air-filled space of variable volume crossing the sound path of the ‘bent acoustic horn’ in the posterior part of the nasal complex.

1A2-M04 体積変化型浮力調整装置を有する水中ロボットの開発 : マイコンを用いた姿勢および水深制御(水中ロボット・メカトロニクス)

The goal of this paper is to develop a robot control system for an underwater robot with a buoyancy control system based on the spermaceti oil hypothesis. Sperm whales have a spermaceti organ in their head that is filled with spermaceti oil. It is said that sperm whales control their buoyancy by melting or coagulating spermaceti oil. In our previous study, we built a depth control system for an underwater robot with a buoyancy control device using the theory. In this paper, a depth and posture control system was built using a microcomputer, a pressure sensor and inclination sensors and so on. In addition, a prototype robot was built using the system. The buoyancy control devices use a piston and syringe mechanism, and paraffin wax poured the syringe. Nichrome wires and peltire elements heat and cool the paraffin wax. From the result of the experiments using the robot, it is conformed that when a target depth and posture were indicated, the robot moved to the targets.

The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru

The modern giant sperm whale Physeter macrocephalus, one of the largest known predators, preys upon cephalopods at great depths. Lacking a functional upper dentition, it relies on suction for catching its prey; in contrast, several smaller Miocene sperm whales (Physeteroidea) have been interpreted as raptorial (versus suction) feeders, analogous to the modern killer whale Orcinus orca. Whereas very large physeteroid teeth have been discovered in various Miocene localities, associated diagnostic cranial remains have not been found so far. Here we report the discovery of a new giant sperm whale from the Middle Miocene of Peru (approximately 12-13 million years ago), Leviathan melvillei, described on the basis of a skull with teeth and mandible. With a 3-m-long head, very large upper and lower teeth (maximum diameter and length of 12 cm and greater than 36 cm, respectively), robust jaws and a temporal fossa considerably larger than in Physeter, this stem physeteroid represents one of the largest raptorial predators and, to our knowledge, the biggest tetrapod bite ever found. The appearance of gigantic raptorial sperm whales in the fossil record coincides with a phase of diversification and size-range increase of the baleen-bearing mysticetes in the Miocene. We propose that Leviathan fed mostly on high-energy content medium-size baleen whales. As a top predator, together with the contemporaneous giant shark Carcharocles megalodon, it probably had a profound impact on the structuring of Miocene marine communities. The development of a vast supracranial basin in Leviathan, extending on the rostrum as in Physeter, might indicate the presence of an enlarged spermaceti organ in the former that is not associated with deep diving or obligatory suction feeding.

Relationship between sperm whale (Physeter macrocephalus) click structure and size derived from videocamera images of a depredating whale (sperm whale prey acquisition)

Sperm whales have learned to depredate black cod (Anoplopoma fimbria) from longline deployments in the Gulf of Alaska. On May 31, 2006, simultaneous acoustic and visual recordings were made of a depredation attempt by a sperm whale at 108 m depth. Because the whale was oriented perpendicularly to the camera as it contacted the longline at a known distance from the camera, the distance from the nose to the hinge of the jaw could be estimated. Allometric relationships obtained from whaling data and skeleton measurements could then be used to estimate both the spermaceti organ length and total length of the animal. An acoustic estimate of animal length was obtained by measuring the inter-pulse interval (IPI) of clicks detected from the animal and using empirical formulas to convert this interval into a length estimate. Two distinct IPIs were extracted from the clicks, one yielding a length estimate that matches the visually-derived length to within experimental error. However, acoustic estimates of spermaceti organ size, derived from standard sound production theories, are inconsistent with the visual estimates, and the derived size of the junk is smaller than that of the spermaceti organ, in contradiction with known anatomical relationships.

Off-axis effects on the multi-pulse structure of sperm whale coda clicks

Sperm whale (Physeter macrocephalus) clicks have a multi-pulse structure, a result of the reflection of sound energy between air sacs in the spermaceti organ. Although previous research revealed that usual clicks (used for echolocation) recorded away from a vocalizing whale's longitudinal axis have waveforms with poorly defined pulse structures, it has been unknown whether sperm whale coda clicks (used for communication) show similar off-axis effects. To address this knowledge gap, a hydrophone array was used to localize vocalizing sperm whales, and the waveforms of coda clicks recorded from different aspects were examined. Coda clicks recorded close to the whale's acoustic axis showed well-defined multi-pulsed waveforms, while those recorded off-axis did not. As for usual clicks, this suggests that sound energy radiates directly into the water upon reflection off the frontal sac.

Killer sperm whale: a new basal physeteroid (Mammalia, Cetacea) from the Late Miocene of Italy

Zygophyseter varolai, a new genus and species of Physeteroidea (Cetacea, Odontoceti), is based on an almost complete skeleton from the Late Miocene (Tortonian) in southern Italy. The extreme elongation of the zygomatic process of the squamosal and the circular supracranial basin (probably for housing the spermaceti organ) delimited by a peculiar anterior projection of the supraorbital process of the right maxilla are the most distinctive features of this bizarre sperm whale. Large body size, large teeth present in both lower and upper jaw, and anteroposteriorly elongated temporal fossa and zygomatic process of the squamosal indicate that this cetacean (for which we suggest the English common name killer sperm whale) was an active predator adapted to feeding on large prey, similarly to the extant killer whale (Orcinus orca). A phylogenetic analysis reveals that Zygophyseter belongs to a Middle-Late Miocene clade of basal physeteroids, together with Naganocetus (new genus for the type of ‘Scaldicetus’ shigensis). Moreover, the phylogenetic analysis shows evidence of a wide physeteroid radiation during the Miocene and that the extant Physeter and Kogia belong to two distinct families that form a clade representing the crown-group Physeteroidea.

Sound transmission in the spermaceti complex of a recently expired sperm whale calf

Sound pulses were projected into the forehead of a neonate, female sperm whale that died following a stranding and attempts to revive it. Two hydrophones, held against the skin, recorded the sound pulses and their reflections. A consistent reflection was found about 0.8 ms after sound projection. This time corresponded to the expected two-way travel time back and forth within the spermaceti organ. Reflections were also detected at the frontal surface of the junk from sounds projected into the distal sac area. These signals must have traversed rearward along the axis of the spermaceti organ to the frontal sac where they were likely reflected and directed forward to the front of the junk, demonstrating an acoustic continuum between the spermaceti organ and the junk. These results support the basic Norris and Harvey (1972) theory of sound generation in sperm whales and later amendments to that theory (Mohl and Amundin (1991), Mohl (2001)).

Sound transmission in the nose of the sperm whale Physeter catodon . A post mortem study

During a sperm whale stranding at Rømø, the Wadden Sea, Denmark, on 4 December 1997, we were notified in time to start acoustic transmission measurements in the spermaceti complex 1 h after the specimen was seen alive. Frequency-modulated sound pulses, sweeping from 30 kHz to 10 kHz in 25 ms, were injected at the frontal surface at two positions: at the distal sac, and at the center of the junk (a compartmentalized structure below the spermaceti organ). A hydrophone next to the projector served as receiver. The analyses of the recordings show a repetitive, decaying reflection pattern at both projection sites, reminiscent of the multi-pulse click peculiar to sperm whales, although with minor differences in the duration of the intra-click intervals. This experimental evidence supports the Norris and Harvey (1972) theory of click generation in the spermaceti organ. Accordingly, the click is composed of a primary event, followed by a train of reflected pulses, spaced by the time required for the event to travel back and forth between air sacs (reflectors) at each end of the organ. The results also show that the junk readily transmits sound and probably is in acoustic contact with the spermaceti organ.

KOGIA PUSILLA FROM THE MIDDLE PLIOCENE OF TUSCANY (ITALY) AND A PHYLOGENETIC ANALYSIS OF THE FAMILY KOGIIDAE (ODONTOCETI, CETACEA)

A partial skull of an odontocete cetacean from Middle Pliocene sediments of Monte Voltraio (Pisa Province, Tuscany, Italy) is examined. This fossil, erroneously referred to the family Ziphiidae and described in the past as holotype of the species Hyperoodon pusillus , is assigned here to the genus Kogia (family Kogiidae). The species Kogia pusilla is redescribed and compared to the living species K. breviceps and K. simus . Phylogenetically, an old separation (at least in the Lower Miocene) of Kogiidae and Physeteridae is suggested. The lack of substantiated kogiid records until the Upper Miocene is probably due to the rarity of these cetaceans. Phyletic analysis within the Kogiidae is undertaken and supposed apomorphies in the morphology and/or the extension of the supracranial basin that houses the large air sacs and the spermaceti organ are considered.

Improved signal processing techniques for measurement of the inter-pulse interval (IPI) of sperm whale clicks

Improved signal processing techniques are described for estimating the inter-pulse interval (IPI) associated with the multiple pulses in a sperm whale click. These pulses are believed to result from repeated reflections of the original pulse within the spermaceti organ in the whale’s head. Previous estimates of the IPI have been based on time series correlation or on computation of the cepstrum of the received waveform [J. Goold, J. Acoust. Soc. Am. 100, 3431–3441 (1997)]. The present work describes real-time computation and display of the spectrogram and cepstrogram (time-cepstral distribution) [G. Pavan, Proc. IoA 19 (1997)] and examines the benefits of the simultaneous display of this information for field analysis and for browsing long recordings to identify sperm whale clicks. In addition, a detailed model of the spectral modulation associated with the multiple pulses is developed and leads to improved estimation of the IPI. Examples are presented that indicate the method may be more robust with respect to additive noise and the effects of surface reflection than the cepstrum-based approaches. [Work of the first author supported by ONR. Work of the second author supported by the University of Pavia, Italy, the Italian Ministry of the Environment, and by the Italian Navy.]