New words for how the biggest blowhole hides a sonic stun-gun
(writing in progress)
The sperm whale (Physeter macrocephalus, https://www.inaturalist.org/taxa/74890-Physeter-macrocephalus) excites our whale-watching tourists as well as being occasionally stranded on Australian beaches.
Despite our familiarity with this species, its full oddness is underappreciated. In particular, what is gradually emerging is that the biggest nose in the world turns out to be a sound-gun, so unlike a true nose that it needs a whole new name: the physetis.
The bulging face of the sperm whale is so peculiar that scientists have fumbled to describe it clearly; and what we cannot put words to, we find difficult to explain.
The various hypotheses about the main function of this facial bulge are gradually resolving to the most plausible but perhaps hardest-to-describe: that the sperm whale has developed extreme acoustics as part of its foraging strategy.
The face of the sperm whale is flesh and cartilage swollen with peculiar lipids – a bone-free mass exceeding 5 tonnes in mature males weighing more than 30 tonnes. This looks like a gigantic bulbous nose, and indeed zoologists write about a ‘nasal complex’ to this day. However, on closer scrutiny the sperm whale lacks any true zoological nose.
Instead, it has invented an odd combination of features with an even odder combination of functions. Until we find apt descriptors, the true nature of the sperm whale may remain an ‘elephant in the room’ to nature lovers – including whale-watching enthusiasts off Tasmania, New South Wales, Albany (Western Australia) and Kangaroo Island (South Australia).
According to the latest research, the facial bulge seems to function crucially as a sonic weapon, i.e. an organ by means of which the sperm whale shoots pressure-waves as effective bullets capable of killing or stunning the species’ usual prey of modest-size squids and fishes. This may sound like extraterrestrial scifi, but it fits the facts if we can overcome the limitations of language.
First, let us briefly compare the face of the sperm whale with those of its relatives, i.e. other toothed whales (cetaceans including dolphins and porpoises). What are the crucial peculiarities of this, the largest species of toothed whale?
The faces of all toothed whales contain a so-called melon, whereby sound is concentrated and amplified for echolocation: ‘seeing with sound’. Toothed whales have lost the sense of smell, and deep-diving whales must forage in darkness. However, water is a noisy environment in which sound travels far faster and farther than in air.
Taking advantage of this, toothed whales bounce sound off objects as a way of locating and identifying prey. Melons – an assortment of roundish boneless structures in the face – contain various mixtures of strange lipids only approximately described as ‘fats’, ‘oils’ or ‘waxes’, the mass of which helps to beam sounds produced by the vocal organs.
Here it is important to realise that the main vocal organ is not the larynx but a novel set of phonic lips deep inside the blowhole – which is located on the ‘forehead’ in all toothed whales other than the sperm whale.
The sperm whale has modified the melon and its acoustic functions in two main ways, as follows.
Firstly, its melon is far larger and more divided than in any other species of toothed whale – allowing extreme concentration of sonic energy at different levels within the facial bulge and at different stages of production of the sound. The sperm whale seems to use its outsize facial bulge to wield power in a way unavailable to terrestrial animals, other echolocators, and most toothed whales. It is capable of continually striking blows with sound to incapacitate the staple species of prey, which are far smaller than giant species of squids.
Secondly, the sperm whale has shifted the phonic lips, associated with the blowhole, from a rearward position on the ‘forehead’ to a forward position near the tip of the facial bulge. This shift of several metres has been accompanied by the reduction of paired phonic lips in all other toothed whales to only one set of phonic lips (on the right side). Despite this reduction, the sperm whale can intensify its predatory screams in a way metaphorically like a bow being pulled back to shoot an arrow. Instead of being beamed immediately forward as in other toothed whales, loud vocalisation is apparently first blasted backward through the top half (‘spermaceti organ’) of the sperm whale’s equivalent of the melon, in an initial process of concentration. The intensified scream then bounces off a reflective air-sac covering the dished bones of the forehead https://www.youtube.com/watch?v=tw7E7owEBm8. The beam of sound is then further concentrated as it shoots forward through the bottom half (‘junk’) of this melon, emerging from the facial bulge and striking prey several or many metres away with remarkable accuracy.
Recently, plucky researchers free-diving with the sperm whale have experienced the effects of being hit by a ‘sonic bullet’ on an outstretched hand: a numbing which can persist for hours https://www.youtube.com/watch?v=zsDwFGz0Okg. So far, nobody seems to have been hit with a brain seizure or heart-attack – whether by good luck or the dolphin-like kindness of the sperm whale. Anyway, imagine what such acoustic force would do to the brains of squids, which rely on relatively sophisticated nervous systems for evading predators.
The sperm whale retains echolocation https://www.youtube.com/watch?v=VhQ3CGSZMqU, in order to locate its prey in the darkness of the deep sea. There is the yet-to-be-studied possibility that these soft, broadcast vocalisations are directed forward by a flexible muscular orientation of the phonic lips, which have an advantage over any larynx of not being boxed by the cartilaginous skeleton. As in all toothed whales, echolocation is sensed not via the melon but instead via the lower jaw.
However, what distinguishes the sperm whale from comparably large toothed whales – particularly the largest species (Berardius bairdii) of beaked whale - is not echolocation but the use of the facial bulge for ‘sonic ballistics’ – i.e. shooting sound with the force to incapacitate the targeted animal.
The shape of the sperm whale shows a trade-off between agility and acoustic power. The same enormous face which reduces streamlining and compromises the mobility of the jaws in catching prey amplifies, concentrates and aims the vocalisations, allowing the otherwise clumsy-headed sperm whale to reach out for prey with its utterances rather than with the deftly beaked mouth so familiar in dolphins.
Zoologists are shy of new terms, and so have lacked apt words for certain anatomical features of the sperm whale. However, perhaps it is time to be bolder in inventing suitable terms. Imagine if we had yet to coin the related technical word 'proboscis’. Our descriptions of elephants might still be at the clumsy stage in which we currently refer to the facial bulge of the sperm whale as a ‘nasal complex’ - which is vague and factually incorrect.
The facial bulge of the sperm whale is unique in several ways begging new terms.
Firstly, in all toothed whales, there is actually no longer any nose in a strict sense, and even the nostril-tubing is so modified as to be hardly nasal any longer. The sperm whale takes this further. The internal nostrils, on the skull, are more asymmetrical than in any other toothed whale. And the arrangement of the external nostrils and the degree of asymmetry in the nostril-tubing are categorically different from any other toothed whale. The result is that the species with the largest-looking nose in the world is actually remarkable for the converse reason: it retains the least nose of any mammal. Whereas any true nose is devoted to smelling and breathing, the facial bulge of the sperm whale is instead devoted to vocalisation, acoustic weaponry, perhaps buoyancy, and – almost incidentally – breathing.
Secondly, the nostril-tubing of the sperm whale stretches the already unrecognisably modified anatomy of other toothed whales almost beyond words. The nostrils of the sperm whale are by far the most asymmetrical in the world, with only the left nostril being used for breathing. Air in the other (right) nostril follows a quite different course and is devoted to vocalisation to the exclusion of breathing. And this vocalisation is different from e.g. the trumpeting produced in the proboscis of elephants, because the sound emerges precisely from phonic lips within the front of the tubing.
Thirdly, the sperm whale is unique in that its vocal organ is located neither in the throat (as in humans and other non-cetacean mammals including other echolocators such as bats) nor in the ‘forehead’ (as in other toothed whales), but instead on its facial bulge. This allows the sperm whale to scream resoundingly because the pressure-waves can be reverberated and concentrated before being shot through the water. The sound beams backwards, bounces off the skull (which is covered with an acoustic mirror in the form of a special air-sac) and then beams forward – apparently being concentrated by what is so misleadingly called the ‘junk’ part of the sperm whale’s melon.
Fourthly, the melon is so much more developed than those of other toothed whales that, again, words tend to fail us. The bottom part of the sperm whale’s melon is enlarged and compartmentalised, with an intricate design belied by its current name, i.e. the ‘junk’. (The disparagement arose because nineteenth-century whalers found relatively little of the valuable ‘spermaceti’ lipids in this part of the melon.) The top part of the melon is awkwardly labelled the ‘spermaceti organ’ and can by itself weigh several tonnes. ‘Spermaceti’ compares the wax-like lipids to the semi-opacity and viscosity of human semen, which is so misguided that the name should be dropped. Might a term such as ‘dorsal hemi-melon’ be an improvement?
There is a subtle possibility of the involvement of the ancestral upper lip in the origin of the facial bulge of the sperm whale. The proboscis of mammals such as elephants and tapirs is derived from a seamless combination of nose and upper lip. The sperm whale lacks the recognisable upper lip of other toothed whales such as the beluga, hinting that the upper lip has been incorporated into the front of the facial bulge, which considerably overshoots the jawbones. The lip-derived part of the facial bulge might even extend as high as the blowhole.
Why are the nostrils and their tubing so asymmetrical in the sperm whale?
The predator must repeatedly and forcefully vocalise deep in the sea despite holding its breath with collapsed lungs, in order to swallow enough modest-size squids and fishes before rising to the surface. The only way to keep its breath up in this way is to recycle a limited quantity of air contained in the nostril-tubing and trachea, where the air is less compressed by the extreme pressure of deep water. The nostril-tubing on the right side, housing the phonic lips, lies deep within the facial bulge, where cartilage limits the compression. And just in front of the phonic lips is an air-bladder which can hypothetically be used to pump a small volume of compressed air back and forth across the phonic lips.
Given the importance of these peculiarities, let us find a suitable name for the whole, complex facial bulge.
I suggest the word ‘physetis’, based on the ancient Greek ‘physa’, meaning bellows. This name is unambiguous and consistent with the genus and family names of the sperm whale (Physeter and Physeteridae). The reference arose because the ancients noticed how similar the respiratory spume of the sperm whale in the Mediterranean Sea looked like the blowing of the bellows already used in the bronze age.
The sperm whale is the largest toothed whale. However, its teeth are its least remarkable feature. The sperm whale can suck stunned prey directly into the gullet even if its teeth are missing. Dentition is relatively unimportant in the foraging of this species, which seems to make little attempt to pursue prey - and forages partly upside-down. Chasing may be unnecessary where the prey can be shot acoustically, like a hunter using a rifle. The blowhole has been radically shifted from its usual position on the ‘forehead’ in other whales, to a position near the tip of the facial bulge, because this allows a particularly powerful acoustic system in which the melon of the sperm whale concentrates and focuses the energy of its vocalisation before propelling the sound forward with sufficient aim.
I propose that the sperm whale possesses not a ‘nasal complex’ but a physetis – which functions not as a nose but as the ultimate example of a ‘sound-gun’ in animals. Can we look forward to the various components of the physetis also being given suitable names, allowing us to discuss this remarkable species more clearly when we next take to our seas as whale-watchers?
(writing in progress)
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