A Gathering of Giants
It was late afternoon and the sun was low in the sky. I’d spent the entire day, and many days prior, scanning the horizon for signs of life. My small boat bobbed up and down in the swell. Every now and then, a wave crest slapped its fiberglass hull, creating a resounding clap and shooting a curtain of spray skyward.
The shimmering glare of reflected tropical light was overwhelming. I squinted and rubbed my eyes as a haze of brine and dissolved SPF 50 blurred my vision.
When a faint puff of condensation shot into the air on the horizon, I thought it was a mirage, an artifact of fatigue and my compromised senses. But when I saw a second, I knew there was only one thing it could be—the exhalation of a surfacing whale. Excitedly, I counted a third, then a fourth, a dozen… no, hundreds!
That’s how I came to witness a phenomenon few have ever seen before.
Skimming over the waves, I stopped the boat a short distance from where I had seen the whales’ last blow and slipped quietly into the sea. I could scarcely believe my eyes.
Hundreds of sperm whales (Physeter macrocephalus) swam to and fro, their huge bodies elegantly twirling and twisting through the water as they socialized. Bumping, jostling, and rubbing themselves against one another, they were exuberantly tactile, their behavior appeared almost euphoric. I felt like a gatecrasher at a wedding, so obvious was their delight in each other’s company.
As my eyes took in this secret spectacle, my ears were assaulted by a cacophony of excited whale chatter. Creaking and crackling, clicks, buzzes, and pops permeated the water as the whales pinged one another with sound. Pulsating rhythms pregnant with meaning penetrated my body. I “felt” the connection between the congregated cetaceans as powerfully as I heard it.
Moving together in groups several dozen strong, the whales occasionally descended to deeper water, but largely stayed near the surface, giving me a privileged view.
Watching carefully, I noticed that two other activities added to the commotion: sloughing of skin and defecation. Like other whales, sperm whales shed skin on a regular basis. This may be a mechanism to reduce the risk of infection and to rid the animals of external parasites. As the whales rubbed against one another, the physical contact dislodged flakes, sometimes entire sheets, of skin, which floated in the water like a blizzard of translucent dandruff.
Group defecation also seemed to play a prominent role. When a dozen or more whales defecated simultaneously, it created a cloud of poop that engulfed the ensemble, obscuring them from view and turning the seawater into an oily soup.
Although the reason for such behavior is not entirely understood, recent research suggests that defecation by large marine mammals plays a vital role in the ocean’s nutrient cycle. Sperm whales, for instance, consume deep-dwelling squids. They then defecate near the ocean surface, releasing iron and other nutrients. This, in turn, supports plankton blooms that help to mediate the accumulation of carbon in the atmosphere.
To understand the factors that contribute to such spectacular aggregations of sperm whales, we need first to consider some basics of the species’ biology and social structure.
Sperm whales are mammals and live in almost every major ocean, including both tropical and temperate waters. They breathe air and are warm-blooded. Yet they spend the majority of their lives in deep, dark, cold water foraging for food, often diving to depths of 800 meters or more in the process. It helps to think of them not as air-breathing animals that dive, but as creatures of the deep that occasionally visit the surface to breathe. In other words, the opposite of how humans relate to the ocean.
Unlike other whales, such as humpbacks, whose existence as it relates to food is best described as feast or famine, sperm whales forage constantly. But the ocean is a big place, and much of it is a nutritional desert, so they are most often found where there is abundant prey. They dine primarily on squid, though they’ve been known to eat fish and octopuses. They also occasionally mistake plastic for prey.
Sperm whale society is structured along matrilineal lines, with adult females and their offspring forming the basis of a social unit. Such units typically comprise a dozen or more individuals, though average numbers and unit structures vary across ocean basins.
Female offspring generally stay with their social units, while males leave as they mature, striking out to form loose groups with other young males. Together, they seek out prey in the nutrient-rich waters of higher latitudes.
Recent research suggests that sperm whales organize their societies and keep tabs on one another using sound. Each individual uses its own “voice,” or acoustic signature, to identify itself, and each social unit uses a set of unique sounds, called codas, that are distinct from those used by other units.
Going even further, multiple sperm whale social units that have similar codas, or “vocal dialects,” and socialize from time to time are known as clans. These larger groupings, which can comprise thousands of individuals scattered across vast regions of ocean, maintain a sense of extended group identity and long-term association through the use and recognition of similar codas.
In other words, sperm whales appear to use acoustical hierarchy to establish identity on at least three levels: self, family, and extended group.
In light of these insights, the factors that likely contributed to the incredible congregation of sperm whales I encountered are easier to understand.
Sperm whales tend to be found wherever the hunting is good—and so, predictably, I spotted the aggregation in a location with abundant squid prey. They are also highly social—and so an encounter involving multiple social units in a given clan produces a riot of sound and energy. It was, in a sense, a vast reunion with plenty to eat and communicate about. But why was a cetacean convention of this magnitude being held?
The short answer is, we don’t know. Other social animals also engage in occasional, large, communal gatherings. Elephants, for example, have matrilineal social units and extended clans similar to those of sperm whales. During the dry season, large numbers of elephants aggregate around sources of water and families may take the opportunity to socialize.
But while there are many potential parallels between sperm whale gatherings and those of elephants, there isn’t enough data or even anecdotal observation at this stage for scientists to draw meaningful conclusions about sperm whale get-togethers. Their exact purpose remains a mystery.
It’s tempting to speculate that sperm whale gatherings like this may have been more common in the days before industrialized whaling decimated their numbers. W.D. Boyer reported coming across an enormous gathering of sperm whales in Peru in 1945, just before the escalation of large-scale whaling. He wrote: “…the entire ocean, to all visible limits of the horizon, seemed spotted with them. The sum total was a school of gigantic proportions… It took the vessel nearly an hour to travel through the main body of the school…”
Although commercial hunting of sperm whales began in the 18th century, the majority of reported kills took place between 1950 and 1980 when harpoon guns became more widely used. Whaling records show that more than 638,000 sperm whales were killed during this period.
Today, population estimates for sperm whales fall in the range of 300,000 to 400,000, down from more than a million whales worldwide before large-scale hunting began. They are currently classified on the IUCN’s Red List as Vulnerable.
Large-scale industrialized whaling ended relatively recently. Because sperm whales reach sexual maturity at a late age—around 10 years for females and up to 20 years for males—and because they produce few young, their recovery has been slow. But perhaps with time and increasing populations, these large aggregations will occur and be documented more often.
Although widespread hunting is no longer an issue, sperm whales still face a litany of threats. Ship strikes cause terminal injuries, fishing gear strangles and entangles them, and ingested plastics block their guts, causing them to starve with full stomachs.
Earlier this year, when 13 sperm whales beached themselves in Germany, researchers found plastic garbage in the stomachs of four of the dead whales. Trash ingested by the dead sperm whales included a nearly 13-meter-long (43-foot-long) shrimp fishing net, a plastic engine cover, and the remains of a plastic bucket. Though most people may have never seen a sperm whale, the byproducts of our modern societies can sometimes reach these marine mammals without our knowledge, and can have devastating effects.
Humans have a long and checkered history with sperm whales. In the past, we feared them. We hunted and killed them. It’s only relatively recently that we’ve taken the time to try to get to know them. What we’ve learned is that far from being fearsome monsters intent on destroying ships, sperm whales are intelligent creatures with complex social and cultural bonds mediated by behavioral nuances that rival our own. And yet so much about them remains a mystery, including their spectacular but secret gatherings.
The fact that we understand so little about such large and magnificent animals, despite our shared history, you have to wonder what else we don’t know about life in the ocean.
Capturing the Spectacle
Photographing sperm whales—intelligent, social animals with wide-ranging territories—in an alien, potentially dangerous, environment demands two things: intimate knowledge of your subjects’ natural history and a level of physical fitness, swimming proficiency, and comfort in the open ocean.
Because whales are so much faster and more agile than a human swimmer, patience and a keen understanding of the animals’ behavior is key to being in the right place at the right time. Wu says that his best photographic opportunities have occurred when photography was not his main priority—when his goal was to observe and learn, and to understand the animals’ behavior.
Entering the water with hundreds of socializing whales can be an intimidating experience. However, after more than 16 years of experience observing, photographing, and interacting with sperm whales and other cetaceans, Wu trusted them not to be aggressive, especially since they were preoccupied with socializing. Still, with bodies bumping and flukes flying, being able to read the whales’ movements and anticipate their actions was crucial to his safety.
Ethics of Whale Watching
Whale watching has become a major source of tourism revenue around the world. A report commissioned by the International Fund for Animal Welfare found that, in 2008, 13 million people participated in whale watching excursions in 119 countries and territories, generating a total expenditure of US$2.1 billion. At that time, an estimated 3,300 operators offered whale-watching trips worldwide, employing an estimated 13,200 people. Those numbers have no doubt risen since then.
The growth in popularity of whale watching has also led to an increase in whale harassment by operators. Many whale-watching tours claim to be environmentally aware and prioritize the cetaceans’ welfare, but this is not always the case. In recent years, Wu says he’s seen far too many operators in speedboats chasing surfacing whales, driving into their paths, and encouraging tourists to jump into the water on top of them.
After long dives, sperm whales spend long periods at the surface re-oxygenating their systems. Wu has observed a whale take as many as 54 breaths between foraging dives. It stands to reason that interfering with a whale’s breathing cycle causes the animal distress. But, faced with an armada of speedboats, he has seen whales dive after taking only 10 breaths. Short of air, the whales then had to resurface again nearby, where swarming speedboats once again forced them to dive prematurely.
Should you decide to watch whales from a boat, or try to get into the water where permitted, Wu recommends doing your homework. Find out if permits are required and have been secured, and try to assess how much the tour operator actually knows about whales, he says.
Learn more about responsible whale-watching practices here.
by Sophie Stafford