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The Sounds of Silence

sound1Into the (Really Noisy) Silent World
By Shane Paterson
Photos by Matt Weedon

You enter the sea and immediately Everyday Life’s cares begin to dissolve. Gone are the stresses and worries that kept you on edge for interminable days and sleepless nights; faded are the competing demands and stacked deadlines that seem to define your existence. At last, in the warm embrace of Mother Ocean, you find the peace that has for so long eluded you. No argumentative Type A personalities stridently pointing out your every weakness and shortcoming. No telephone ringing with intrusive salespeople interrupting your dinner to push pointless products. No blaring television repeating the postmodern mantra “Buy! Consume! Vote for me!” ad nauseum (undoubtedly Latin for “nauseating ads”).

Gone are the teeth-rattling, bass-heavy absurdities that disturb your early-morning tossing and turning as an overstereoed car cruises by on ridiculously undersized wheels. Gone too is the clock radio’s dreaded blaring at some obscene hour of the morning. There’s just a tranquillity that, if anything, is paradoxically overwhelming in its very lack of auditory stimulation. You float above a peaceful realm of coral and sand spread beneath a shimmering turquoise skin of sea and an impossibly blue sky. A world of quiet and calm. A languorous place that Jacques Cousteau dubbed the “Silent World.” Peace at last. Right?

Actually, not really. The Silent World really isn’t. Silent, that is. Not always, anyway. The sea’s subaquatic sounds are more subtle than many of those from our world of air, and more muted and infinitely less jarring than those made by humans, but the sea is not a place devoid of sound.

Don’t take my word for it; you’re in the Turks & Caicos Islands, so give yourself a few hours’ break from whatever you’re doing, strap on a snorkel or SCUBA tank, and go looking for silence in all the wrong places.

SNAP, CRACKLE AND POP

The first thing that you might notice upon getting your ears below the waterline is a continual (and loud) crackling that is perhaps best described as being what you’d hear if you were ever trapped in a bag of popcorn that had reached popping temperature (undoubtedly the late Orville Redenbacher’s recurring nightmare).

Some of the shallower Turks & Caicos reefs seem particularly good proof of this, ablaze as they are with an intense crackling rarely heard beyond the oily confines of a hot frying pan or wok. The main culprits are pistol, or snapping, shrimp. It’s only recently been demonstrated that they produce sound through cavitation–opening and closing their claws at such a phenomenal rate that they create and pop bubbles. The mechanics are thus somewhat similar to those behind the rude noises that male children produce via their armpits, but these bubble-bursting shrimps can produce sounds well above the decibel threshold at which humans begin to experience ear pain. Even the Who’s guitar-murdering Pete Townsend is an auditory lightweight by comparison. You never see these shrimps, but you know they’re there. In their way, they’re the most easily identifiable of the reef’s denizens–you don’t even really need to see them. The bubble-blowing is far from aimless, too: benefits to the shrimp include communication with others of their species and probably rapid incapacitation of the worms, small fishes, and crustaceans upon which they feed.

Grunts

Then there are grunts, joining together to form those gold and blue or silver masses that you’ll see hanging out in the lee of a large elkhorn coral or along the edge of just about every shallow reef in these islands. Ever wonder how grunts got their name? Invade one’s personal space too quickly and you might find out. A mild-mannered grunt’s bark is worse than their bite, but the sound can still take you by surprise. And that, as we’ll see shortly, is the whole idea.

SONGS OF LOVE AND DEATH

Sound waves travel almost five times faster underwater than in air, so sound can be a very effective means of communicating over distances long and short. As many as 300 fish species may produce sounds of one kind or another. Toadfishes whistle or make high-pitched “foghorn” sounds, squirrelfishes grunt, drums–well–drum, sea robins sing (if not quite like their terrestrial namesakes), and groupers can actually boom at you if you happen to catch them by surprise or if you’re cad enough to harass one.

Many of the sounds that fishes produce use frequencies too low for unaided human detection, but the booming of a grouper is hard to miss. A big grouper, such as a Goliath grouper (formerly known as the jewfish, only recently renamed after a Philistine with growth hormone problems), can muster up enough of a sonic boom to give anyone a start. If you’re boomed at by a grouper, back off to give it some space and a bit of respect. Besides, you probably don’t want to be rammed by any grouper, let alone one that looks to be the approximate size of a Volkswagen.

It’s probably just a function of them being studied the most, but damselfishes seem to have a particularly complex system of sounds that, in concert with particular body movements and postures, form the basis of complex social systems. As seems to be the case for most other fishes that use sonic communication, damselfishes make the most noise when they’re facing down a potential predator.

Propagating the species is, when you come down to it, what life’s all about. But it’s hard to get much propagating done when you’re dead, so staying alive in a predator-field sea is as vital a concern to your average fish as is reproduction. Sonic ability comes in handy here, too. A fish that emits an alarm call when frightened, or when in the jaws of a predator, might startle the predator into hesitating long enough to allow escape. That’s Plan A. If that doesn’t work, the doomed fish’s calls may not be in vain–others of its species may benefit from the warning and, if the fish is really lucky, a competitor to the predator, or perhaps a bigger predator, will come to see what the fuss is about. That’s Plan B.

Damselfishes and others are also pretty vociferous when they’re indulging in courtship behaviour. Sounds come into play whether the male is wooing the female–preening like Travolta’s character in “Saturday Night Fever” and tearing loose with fishy versions of wolf whistles and “hey, bay-bee” that’d put many a chauvinist human to shame–or defeating, by intimidation, rivals for her affection. Female damselfishes can distinguish the size, identity, and location of would-be suitors just from the nature of their calls.

sound3Such sounds are sometimes the piscine equivalent of serenading beneath a senorita’s window and sound production is an integral part of the courtship ritual for many fish species. Large groupers even flaunt their heavy bass rumble in such situations, each basso profundo trying to outdo the other. Barry White would understand.

Incidentally, although no shark has yet been identified that produces sounds equivalent to those gracing recordings by the “Walrus of Love,” British aquarists around this past Valentine’s Day opined that piping Mr. White’s velvet-voiced crooning into shark display tanks might enhance the sharks’ reproductive motivation in a manner remarkably similar to that previously demonstrated for humans. Truth continues to be appreciably stranger than fiction.

STRIDULATION, CONVERSATION & SONIC BOOMS

Fishes produce sounds in several different ways and sometimes use a combination of different approaches, like an orchestra conductor choosing instruments to build just the right sound. Some fishes, such as grunts, produce sound by basically grinding their teeth together. A few, including marine catfishes, have specialised fin elements that move within sockets to produce loud clicks.

Many fish species produce sound by contracting muscles around their swim bladders, the gas-filled swim bladder functioning both in buoyancy control and as a kind of echo chamber in sonic communication. Some of the drum-like sounds that fishes produce are pretty obviously muscles vibrating against the swim bladder, but even some of the whistling and other high-pitched sounds derive from the same mechanism. The basic mechanism–stridulation is the name given to the shrill noise produced by rubbing body parts together–is essentially the same as that in cicadas and other insects that produce noise by rubbing their legs and wings together. When the muscles contract fast enough, the sound that issues forth may sound like anything but a drum. Rates at which these muscles contract around the swim bladder can be incredible–the oyster toadfish’s whistle, for example, is the result of muscles moving against its swim bladder a phenomenal 200 times per second, a Herculean effort sustained by the fastest-twitching muscles yet discovered in any vertebrate animal.

The virtuosos of marine bio-acoustics are unquestionably dolphins and other whales. Here we enter a whole other realm of communication, because some of these animals almost certainly possess full languages by any definition. If you’re lucky enough to be anywhere near the Columbus Passage during the winter, you’ll probably hear the mournful sound of a passing humpback’s “song” as it moves to or from breeding grounds on the Silver Banks between Grand Turk and the Dominican Republic.

These sounds can travel for hundreds, or even thousands, of miles. It’s the marine mammal equivalent to the Internet, by which whales within a hemisphere may remain in contact and pass along information. Just as humans have kept alive ancient sagas passed by oral tradition to the present day, so may certain whales tell stories about past and present, including the oceanic equivalents to traffic advisories, weather reports, and restaurant critiques.

Among smaller whales, dolphins are well known as successful hunters that use echolocation to find prey and to probe murky waters, but they also have a variety of vocalisations that seem to form at least a rudimentary language. Dr. Doolittle wished that he could talk to the animals and now dolphin researchers in Hawaii and elsewhere are doing their best to fulfill the same vision.

The Turks & Caicos Islands have long been known as home to JoJo, a dolphin who has proven to many that there are means other than the sonic with which to communicate. Still, “talking” is important to dolphin social behaviour. In killer whales, acoustic ability even has direct predatory application–these huge dolphins can focus intense blasts of high-pitched sound that actually stun the hapless prey. Recent research suggests that bottlenose dolphins, including JoJo, may share that predatory capability.

SOUNDS OF THE SEAS

sound2The ocean echoes with sounds from plenty of other sources. Although real-life sharks are not generally accompanied by the ominous sound of a cello, large fishes and whales can produce sound merely by passage of their body through the water. Such hydrodynamic sounds can be quite distinctive, as are the sounds of whales slapping, mantas jumping, and flyingfishes skimming. Human sonar operators on navy ships and submarines quickly become adept at sorting out this cacophony of natural sounds and, as if a small fish on alert for sharks, listen for the characteristic hydrodynamic noise of a predatory submarine in the neighbourhood.

Human activity, of course, adds its own noises to the seas- quiet symphony. Unfortunately, but not particularly out of line with our other contributions to the marine realm, our noises all too often interfere and overwhelm. Figuratively speaking, we’re breaking loose with arrhythmic punk-rock chainsaw-guitar riffs in the midst of a well-orchestrated Mozartian melody. Debate currently rages over U.S. Navy testing of powerful Low-Frequency Active Sonar, designed for submarine warfare, that interferes with whales’ hearing and navigation abilities and appears directly fatal because of decibel levels far higher than those deemed unsafe for humans.

Then there are the sounds of the sea itself, most obvious to a diver where the sea spends its awesome energy against an ironshore coast or dissolves upon an empty stretch of sandy beach.

Hardly quiet, and frequently anything but placid, the (Relatively) Silent World still offers undeniable respite from the rigors of Modern Life. Listen to the sand sift across a narrow gully in the reef. Wince at the grating sound of a large parrotfish reducing living coral to white sand. Let your ears fill with the castanet sound of shrimps as they reveal the true sound of one claw snapping. Escape the noise for a little while and hear the sounds of nature. It’s a Noisy World, after all

Shane Paterson, who studied great barracuda while a visiting scientist to the School for Field Studies on South Caicos, is currently a Postdoctoral Research Scientist at the Bermuda Biological Station for Research. Matt Weedon, who worked in the Turks & Caicos Islands as a School for Field Studies intern and as photo pro aboard Peter Hughes Sea Dancer liveaboard dive vessel, is a professional photographer now based in Texas.



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Marta Morton, owner/operator of Harbour Club Villas (www.harbourclubvillas.com) took this photo of the native Turks & Caicos rock iguana on Bay Cay. This endemic animal is being threatened by the invasive green iguana. See article on page 36.

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