A whale’s death can spark a fascinating natural process. Initially, the carcass might drift on the ocean surface, attracting predators like sharks. As it weather’s away, it begins to sink, eventually settling on the ocean floor, where deep-sea scavengers feed on it.
Records of whale falls are limited and often incomplete. However, a team of scientists led by Xiaotong Peng from the Chinese Academy of Sciences recently uncovered a massive, ancient whale burial site in the Diamantina Zone in the southeastern Indian Ocean. Published in Nature, this discovery dates back over 5 million years and is one of the deepest known whale-fall ecosystems anywhere in the world.
During a specialized expedition in February 2023 using the submersible Fendouzhe, researchers found extensive whale skeletons and fossils partially buried in sediment on the seafloor. Over the following month, they conducted 32 additional dives, mapping a necropolis that stretches for approximately 1,200 kilometers (746 miles) along the ocean floor at depths ranging from 4,200 to 7,000 meters (13,780 to 22,966 feet). The site contains 476 whale fossils and five active whale falls, which are teeming with strange sea creatures such as jellyfish, brittle stars, and bone-boring worms—many possibly new to science.
From the fossils recovered, scientists identified five species of beaked whales, including the Andrews’ beaked whale (Mesoplodon bowdoini), the strap-toothed whale (Mesoplodon layardii), both known inhabitants of the region, plus a baleen whale—the sei whale (Balaenoptera borealis). The largest find was a dead Antarctic minke whale, measuring 5 meters (16.4 feet), identified through its ear bone shape and genetic testing. They also discovered a new extinct whale species, Pterocetus diamantinae.
Radiometric dating indicated that the oldest fossils are approximately 5.3 million years old. The dense concentration of whale remains raises questions about how this whale graveyard formed. Researchers propose that the V-shaped topography of the Diamantina Zone may funnel carcasses toward the seafloor, especially since many deep-diving beaked whales live in the area.
This discovery deepens our understanding of whale falls and the unique ecosystems they support. It also offers valuable insights into beaked whales—offshore species capable of diving up to 1 kilometer (0.6 miles) and holding their breath for over an hour. The presence of 5-million-year-old fossils provides a rare glimpse into the evolutionary history of beaked whales from the Pliocene epoch to today.
Overall, this finding highlights how little we know about the deep ocean—and how exploration can reveal not only what we seek but also a wealth of unexpected discoveries.
Written by Vanessa Pirotta, The Conversation.