What Is a Whale Graveyard?

You might have heard of elephant graveyards—that is, the final resting places where, according to legend, old, dying elephants head instinctively after leaving their herds. These sites, filled with the bones of many elephants, have long captured the human imagination. Scientists, however, generally reject the idea that elephants seek out these locations by instinct. Instead, they suggest that concentrations of bones are the result of environmental factors. For example, drought often concentrates elephants around water and food sources, such as watering holes, where those sick or weakened by starvation are more likely to succumb to the harsh weather conditions, poor water quality, or predators who have taken notice of the herd’s behavior.

But what about whales? What happens to these “elephants of the sea” when they die?

Whale falls

Researchers have discovered whale graveyards on beaches and inland areas (such as Wadi Al-Hitan [Whale Valley] in the Western Desert of Egypt and near the Pan-American Highway in Chile’s Atacama Desert). Other necropolises stem from whale falls (that is, the sudden arrival of a whale carcass on the ocean floor), but their origins appear to be shaped by forces unique to oceans themselves. As with all animals, when a whale dies, bacteria begin the process of decomposition. The waste gases produced by bacteria build up in the whale’s tissues and make the carcass buoyant enough to float on the surface of the open ocean for a time. As the carcass drifts on the surface, it is pushed by ocean currents and scavenged by sharks before the gases dissipate.

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Bereft of its buoyancy and some of its mass, the whale’s remains fall into the cold, dark depths, where decomposition continues. Researchers note that most whales expire and sink in waters tens of meters to about 4,000 meters (about 13,100 feet) deep, usually landing in the ocean’s abyssal plains (vast areas of the ocean floor that sit between 3,000 and 6,000 meters [about 10,000 and 20,000 feet] deep and are largely devoid of life). Since abyssal plains are the largest habitats on Earth’s surface, finding large concentrations of whale carcasses there are rare.

Two types of graveyards

It turns out that whale graveyards comprising whale skulls, vertebrae, and other bones are found in two distinct types of settings. Whale graveyards have been found in beach or inland environments, which may have been the sites of mass strandings (see cetacean: stranding). In these areas the fossilized whale bones of whole pods are typically covered by layers of sediment—usually sand, silt, and rock sloughed off mountainsides or deposited by floods of nearby rivers. Other whale graveyards occur far from land; for some whales that die in the open ocean, their bones have been shown to collect in deep-sea trenches.

The largest and deepest of these whale graveyards was discovered in the Diamantina Fracture Zone—a deep-sea trench located about 1,400 km (about 870 miles) off the coast of Western Australia in the Indian Ocean. A team made up of researchers from China, Italy, and New Zealand who were exploring the trench in a submersible in 2023 stumbled upon a deep underwater valley containing millions of bones and bone fragments resting on the seafloor.

After surveying only a tiny fraction of the trench, the researchers tallied 476 individual whales spanning a variety of species. After collecting a number of samples with the submersible’s remote arm, the researchers revealed that the bones dated from the present day back to at least 5.3 million years. The remains stemming from recent whale falls—which were still being processed by thousands of invertebrates, including clams, worms, and brittle stars (many of which were likely new to science)—were thriving biological communities. In addition, many of the fossilized remains belonged to beaked whales, an elusive group of toothed whales, both present and extinct, which offers paleontologists a tantalizing opportunity to map beaked whale evolution and speciation. These fossils were found partially buried at the bottom of the trench and required little in the way of excavation because they were so far from the sources of rock and sediment that slide off of continents; sediment deposition rates in the Diamantina Fracture Zone are tiny, up to 0.55 cm (about 0.2 inch) every 1,000 years.

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The researchers suggested that the abundance of beaked whale fossils in the trench may be the result of these deep-diving whales succumbing to conditions as they ventured beyond their pressure tolerance and endurance limits in search of food. Also, the V-shaped cross section of the trench likely directed falling whale carcasses to the trench floor. The research team plans to return to the Diamantina Fracture Zone to survey the rest of the trench in the hopes of finding more whale fossils and new forms of life, and the discovery raises the possibility of learning more about whale evolution by exploring the ocean’s other deep-sea trenches.

Although whale graveyards, like those of their distant terrestrial cousins, are probably not the result of mystical gatherings of animals near death, they are still places filled with wonder and fascination. They represent points of convergence where biological activity, oceanographic forces, seafloor features, sediment accumulation, and deep-sea ecosystems mingle across time.