Spying on Whales: The Past, Present and Future of the World’s Largest Animals. Nick Pyenson
dwarfed the tools at hand, the decay of flesh accelerated by nice weather or retarded by wet and cold conditions. The work was certainly not glamorous. And there were no modern winches or cranes, nor photographs to document the findings. Just ink, paper, and a strong stomach.
A stranded whale affords a detailed look not merely at diagnostic traits—a ridge along the snout, a piebald underbelly, or a knuckled tailstock—but at its inner anatomy, musculature, and organ systems, which can’t be described from a boat. In the early nineteenth century, the first naturalists to roll up their sleeves and describe what they saw were enabled by an emerging infrastructure for scientific reporting—published scientific proceedings. By writing down, illustrating, and sharing what they saw, they created the basis for others to seek out their own comparisons. Even Aristotle knew that whales were mammals, but these first detailed dissections revealed facts of their inner world that were equally familiar and puzzling: they had a heart, lungs, a stomach, an intestine, and a reproductive tract just like a dairy cow or a tax collector. The early scholarship generated by careful anatomical work on whale strandings had serious impact on science, surpassed only by anatomists working under more stable laboratory conditions, with the benefit of refrigeration and power tools, generations later.
While today we know that, for instance, blue whales off Ireland, California, and South Africa all belong to a single species, naturalists in the eighteenth and nineteenth centuries did not. With incomplete (and sometimes incorrect) descriptions of other large whales, naturalists puzzled by variations in color or size would sometimes create a new scientific name based on a single stranding, or judge that a whale’s appearance far from another record merited its description as a new species. It took until the early twentieth century for Frederick William True, one of my predecessors at the Smithsonian, to unravel these issues for large baleen whales and demonstrate that blue whales, humpbacks, and fin whales, among several others, were the same species on both sides of the Atlantic—despite dozens of taxonomic names purporting otherwise. True spent years working with original name-bearing specimens (called type specimens) for these different species, doing what taxonomists largely regard as housecleaning—a time-consuming task involving chasing specimens that are archived around the world’s museums and figuring out their identity.
Even today there are some species of beaked whales known only from skulls washed up on a beach—yes, in the twenty-first century there are several ton-heavy species of mammals in our planet’s oceans whose scientific basis primarily relies on a single beach-cast skull. Beaked whales are among the deepest-diving whales, looking something like a bottlenose dolphin crossed with a submarine. In fact, we know very little about most species of beaked whales, which account for nearly a quarter of all whale species alive today—they simply live too far at sea, dive too deep, and are incredibly difficult to tag or photograph in life. Without museums to house the rare remains that do turn up, we would know far less about these enigmatic species.
Not every whale that dies washes ashore, of course. Whalers for several hundred years have known that some whales float after death while others sink. Dead sperm whales float because of the enormous oil chambers housed above their faces, as Yankee whalers knew well. Right whales earned their moniker because they were the right whales to hunt, and they float after death because of their massive blubber layer, a trait they share with bowhead whales, their close relatives of the Arctic. Other large baleen whales, such as blue or humpback whales, will sink after a prolonged time at the surface, although carcasses can refloat following enough decay, when the gases from decomposition make the carcass buoyant. It isn’t uncommon to see the large throat pouch of some of these whales balloon after death, like an emergency air bag that somehow failed to deploy properly in life.
Beyond these facts, known mostly to whalers and beachcombers, no one really knew much more until 1977, when a U.S. Navy submarine cruiser accidentally discovered a gray whale carcass on a seafloor more than four thousand feet deep, west of Catalina island, off the California coast. Of course, we already knew that some whale carcasses fall through the water column and reach the ocean floor, well beyond the depth that light penetrates—it’s just that no one had ever seen the result until then. The scientists who later worked up the growing number of these discoveries called them whalefalls.
At thousands of feet deep, the seafloor is not merely cold and bathed in black; its surface is mostly barren—until a carcass lands, ending its transit through the water column, an elision between two worlds that began with the whale’s last breath at the surface. Whatever flesh that has not already been picked away by sharks or pecked by seabirds provides immediate food for scavengers, such as deep-sea sharks, fishes, and crabs. (How, exactly, they find a fallen whale remains a mystery.) In very little time—researchers estimate weeks to months—these creatures will strip the carcass of its flesh, leaving only bone. On the deep seafloor, there’s little current to disturb the position of the bones, leaving the skeleton looking mostly how it looked as it fell through the water column: the jaws close to or in direct articulation with the skull, which itself is connected to the vertebral column, in a straight line, with arm and flipper bones off to each side, assuming these parts weren’t ripped off by scavengers at the water’s surface.
But once seafloor scavengers swim and scurry away, the story isn’t over. Scientists aboard deep-sea submersibles have set out in search of whalefall skeletons and even experimentally sunk whale carcasses to predetermined locations to learn more. With enough replications and time, they found that whalefalls undergo successive phases, not unlike a forest ecosystem that changes in composition and size as it matures over decades.
Once defleshed, whalefalls undergo a second phase of colonization by snails, clams, and polychaete worms—some feeding off cartilage and the surfaces of the bone, others burrowing into the apron of sediment around the skeleton, enriched by the organic material leaching off the whale’s blubber and oil. The snails, clams, and polychaetes take months to a few years to consume all that they can, and afterward a third phase begins, which can last decades or more (no one knows because whale-falls have been studied for only forty years). This presumably final climax stage involves two sets of bacteria living in or on whale bones: anaerobic bacteria that use sulfate in the seawater to digest oil locked in the whale’s bones; and then sulfur-loving bacteria that use the sulfide by-product of the anerobic bacteria to generate energy by combining it with dissolved oxygen. Sulfophilic bacteria support a variety of true whalefall specialists at this stage, including some mussels, clams, and tube worms that have the bacteria living symbiotically within them, giving them the opportunity to generate their own energy in a world devoid of sunlight. At these depths, whale carcasses give a second life to an otherwise barren, abyssal world.
While the precise duration of these skeletons on the seafloor remains unknown, the upper bounds of some estimates suggest that a single whale carcass can provide up to one hundred years of sustenance. So little is known about the breadth and variation in whalefalls that new discoveries are being made all the time: one is an organism called Osedax—literally, Latin for “bone devouring”—a species of deep-sea worm whose entire life cycle depends on whalefall skeletons. Appearing as pinkish filaments only a few millimeters long covering the surfaces of bone, Osedax does not have a mouth or a gut, just wavy tendrils called palps facing outward. Instead of harboring symbiotic bacteria that use a sulfur-based pathway for decomposing bone lipids, its symbionts are a type of bacteria that mobilize proteins directly from the bone itself by dissolving it, using a tangled mat of bacteria-filled roots burrowed into the bones.
Not all whalefall colonizers are specialists; some are generalists that also make appearances on hot vents and methane cold seeps deep on the ocean floor. The range of the temperatures and environmental settings across these deep-sea habitats has led some scientists to argue