The Death of a Whale

In 1970 A sperm whale carcass washed onto a beach near Florence, Oregon. Officials of the Oregon Highway Division, in consultation with the United States Navy, were concerned about the unbearable stench such a huge carcass would produce for a year or more and were at a loss about what to do at first. They decided to break up the carcass and thus facilitate its removal by scavengers. To accomplish this, they surrounded the whale with twenty cases (a half-ton) of dynamite. Soon after the fuse was lit, there was a stupendous rain of blubber chunks for 800 feet all around, one of which smashed a car a quarter of a mile away. These results, curiously, had not been fully anticipated.

Another stranded sperm whale (sixty tons), which beached near Tainan city in Taiwan in January 2004, also made headlines. This one was loaded onto a truck and taken to a university to be autopsied. But when the truck arrived, permission was denied. Later, on its way to a wildlife reservation for disposal of the carcass, the truck drove through the center of Tainan, where, on a busy street, the gases produced by internal decay caused the whale to explode. Aside from the nauseating gas, a shower of entrails and blood rained down on shops and people, and although the crowd tried to disperse, the hubbub stopped traffic for hours.

These mistakes were not repeated in 2007 at another whale carcass (seventy tons) that washed onto a beach in Ventura, California. This carcass attracted a huge crowd, but the Ventura County Parks Department had bulldozers dig a fifteen-foot-deep hole in the sand rather than fragmenting it by dynamite. The whale may, however, already have been punctured, as it (along with another whale around that time) was likely a fatality from a collision in the busy shipping lane of the Santa Barbara Channel. Unfortunately, most of the sand around the carcass washed away. Oil and rotting flesh leaked out, making nearby beaches uninhabitable.

We don't know how whale carcasses would have been disposed of in the Early Pleistocene and before. But beaching on land would have been rare, so scavenger specialists would probably not have evolved specifically to handle whale carcasses on land --- just as we humans haven't worked out an appropriate protocol for this situation. Any stranded whales would have been used opportunistically by dire wolves, condors, and perhaps the American lion and saber-toothed cats who happened to be near.

The natural process of whale recycling presumably begins near the surface of the water. We know little about a whale's natural death, but we can imagine a scenario of what it may look like. Perhaps the whale weakens from old age and then drowns. I suspect that a weakened whale might easily become prey to orcas (killer whales), who hasten its death. After the orcas have taken their fill, the blood would attract large sharks, such as the great white, and various smaller sharks would come flocking to fresh meat. The whale's body cavity would be breached, organs removed, and the lungs deflated. What happens then?

The whale carcass begins to sink, drifting through a nether-world of dark, cold water populated by an assemblage of creatures that are specialized to live off the largess that comes down from above. These creatures seem bizarre to us because they are configured differently from those we know well. Some of the fish have light-generating organs, including one that resembles a lantern suspended from a stiff rod. Some have mouths that are larger than their bodies, with huge teeth. There are females who carry around tiny males that are like parasites embedded in their flesh, an adaptation that compensates for the difficulty of meeting a mate --- something we take for granted in a world of light.

But these creatures don't catch all the manna that drifts down. Some parts of the whale continue to drift all the way to the bottom. Below a depth of 15O meters, photosynthesis cannot occur, so only animals, not plants, exist at lower depths. Those that have adapted to survive there either live on the largess from above or they catch and eat each other. Many are transparent. No light would be visible to us in this deep-water world, but the eyes of some of the animals are enlarged and especially well developed; those with some vision can more easily prey on those who see less and swim above them. Still farther down, where there is absolutely no light from above and no animal can see images, as we do by the light reflected from objects, the animals generate their own light. Prey animals obviously do not "want" to be seen, but they may need to be visible in order to be found by potential mates. At these depths beyond sunlight, there is a continuous light show of flashing and glowing blue lights that have different meanings, from (presumably) attracting mates to luring prey to faking out potential predators; one copepod has been observed to discharge its own light-generating matter (bacteria?) into the water to hide its location, much as some octopi conceal themselves by squirting ink. This is the world of the "engulfer eel," which hangs in the water and presents a long tail to make contact with drifting edible debris or swimming animals. It has a mouth big enough to swallow animals its own size. A forty-meter-long colonial jellyfish has plenty of surface area for contact with drifting food particles. Here lives the fangtooth, a grotesque fish with an appropriate name. It moves very slowly and uses sensory filaments extending from its body to detect nearby objects in the dark by touch or subtle movements of the water.

Finally, the whale, after sinking through strange dark worlds for many miles, comes to rest at the bottom. Here temperatures are near the freezing point, and bodies could potentially pile up forever in this refrigerator. But whales have been on earth in recognizable form since the Eocene, about 54 to 34 million years ago, and through all this time they must have been recycled, or the oceans would now be filled to the brim with their cold carcasses. Such a massive food bonanza as whale carcasses, drifting down to the ocean bottom over millions of years, would presumably have prompted a retinue of specialized scavengers to evolve to make use of them. Until recently we had no idea who these scavengers were or how they recycled the world's largest mammals.

Most of the oceans' ecosystems are ultimately dependent on the sun's energy captured at the surface. In the last decades, however, two new ecosystems have been discovered that suggest other possibilities for life. Deep in the ocean trenches, we now know vents like belching chimneys spew out water heated to 400 degrees F and containing hydrogen sulfide (familiar to us as the rotten-egg smell), and some bacteria are able to use this chemical as an energy source. In this deep-water ecosystem, life is driven by chemosynthesis rather than photosynthesis. Shrimp and other organisms graze on the bacterial mass the way antelope graze on grass. Some of these bacteria have also evolved to live in symbiosis with animal cells. This is similar to the way chloroplasts evolved from algae living in symbiosis with cells and to the way bacteria evolved into mitochondria, allowing animals to live off plants or plant eaters. In this recently discovered ecosystem of the "smokers," sulfide-eating bacteria feed worms, clams, crabs, and potentially many more organisms. A second newfound ocean-bottom ecosystem is fed by methane gas generated from "cold seeps." The methane is first captured by bacteria living in symbiosis with other organisms and feeding on the carbon compounds scavenged from them.

Beyond these two ecosystems is a unique third one, which depends on dead whales. Like the salmon traveling hundreds of miles upriver to die, those whales come from a different ecosystem, namely, the top layer of the ocean, which is driven by photosynthesis.

At depths below 2,000 meters there is almost no free oxygen, and temperatures range from 30 to 36 degrees F. In these conditions bacterial decay as we know it is either nonexistent or very slow. This point was proved in an unplanned experiment by the submersible vessel Alvin, built in 1964, and operated by the Woods Hole Oceanographic Institute, which takes two scientists at a time to great depths. In October 1968, while Alvin was being transported by a ship, a steel cable snapped, and the submersible sank 1,500 meters (5,000 feet). When Alvin was recovered ten months later, a cheese sandwich that had been left inside had not changed visibly, and someone was able to eat it. In those conditions, how would a 160-ton blue whale carcass be disposed of?

After being recovered, the Alvin was rebuilt, and since 1977 it has made hundreds of dives to advance our knowledge, especially of the deep hydrothermal vents at the midocean ridges. In November 1987 Craig Smith, a University of Hawaii oceanographer, was on a routine mission of the Alvin, using scanning sonar to explore the muddy bottom of the Pacific Santa Catalina Basin at a depth of 1,240 meters (4,070 feet), when he thought he saw a fossilized dinosaur. Instead it turned out to be the 21-meter-long skeleton of a blue whale. The crew was astonished to see it surrounded by mats of bacteria and clams. This sighting marked the beginning of the study of "whale falls, as they are now called. Since that first discovery other whale falls have been found, and some have been deliberately created so that scientists can examine the progression of scavengers. The ongoing observations and studies show many specialist undertakers on whale carcasses, including previously unknown animal species.

We now know that, despite the low temperatures, the whale's flesh is fairly rapidly consumed by a succession of mobile scavengers after the carcass first settles on the sea floor. Numerous large, slow-moving sleeper sharks, which can live at great depths, move in, followed by swarms of eel-like hagfish, which burrow into the meat and absorb some of its nutrients directly through their skin. Rattail fish, stone crabs, and millions of amphipods (tiny crustaceans with laterally compressed bodies) also join the feast. This stage of feeding may be completed in months or a year, or up to two years with a very large whale. The bones take the longest to be recycled because their great bulk makes them resistant to access. Herman Melville, in Moby Dick, vividly describes the massive forty-odd vertebrae in a ninety-ton sperm whale as a "Gothic spire: the largest vertebra "in width measured something less than three feet, and a depth of more than four."

After the soft tissues are consumed, a mat of bacteria colonizes the bones, and limpets and snails graze on them. The carcass becomes surrounded also by a dense mat of polychete worms, each around five centimeters long and superficially similar to centipedes. The worms cover the whole carcass in densities of up to 40,000 individuals per square meter. They take everything they can, and after they leave, an abundance of other species moves in. These thrive mainly on the nutrients remaining in the fat within the bones. Bacteria break down this fat in the absence of oxygen and produce sulfur dioxide as a byproduct; this, in turn, uses chemotrophic synthesis (as in the thermal vents) to produce organic molecules, much the way plants fix carbon dioxide through photosynthesis. As in a sunshine-driven ecosystem, animals in the whale-fall community live off the chemotrophic producers, some of which live inside the bodies of others, just as chloroplasts (from ancient algal symbionts) live in plants. Certain clams and tube worms don't need a gut because the chemotrophic bacteria they contain produce organic molecules directly within their bodies. Small Osedax "zombie worms" (Osedax --- Latin for bone devourer"), also with no digestive tract, tunnel into the bones to allow symbiotic bacteria to feed on fats, which the worms absorb into their bodies.

More than four hundred species of macrofauna (this category excludes bacteria) have been identified in whale falls, with at least a hundred at any one carcass. Tens of thousands of individual animals of many kinds may be at work decomposing a single skeleton at any one time. This stage can last ten years, and some think it may be close to a hundred years before the whale's decomposition is complete.

A whale fall is like a species-rich island. It is colonized by yet unknown means, in that the colonizers appear as if out of nowhere. Whale falls are habitats that contain specialists; they are hot spots of species diversity as well as sites of evolutionary novelty. The massive reduction in whale populations from excessive hunting in the nineteenth and twentieth centuries has surely spread these temporary "islands" of life far apart. We may wonder how far apart they can be before they are beyond the reach of colonizers, which would then die out.