Newly-discovered whale graveyard dates back millions of years

**Shamini Bundell** (0:23)
Welcome back to the Nature Podcast. This week, a newly discovered whale necropolis.

**Benjamin Thompson** (0:29)
And turning plant material into chemical building blocks. I'm Benjamin Thompson.

**Shamini Bundell** (0:35)
And I'm Shamini Bundell. A team of researchers have made a completely unexpected discovery seven kilometers below the surface of the Indian Ocean.

**Peng Xiaotong** (0:59)
When we at the seafloor, we didn't know what it is. But when we get back to the laboratory, we found, oh, this is straws.

**Shamini Bundell** (1:12)
This is Zhao Tongpeng from the Institute of Deep Sea Science and Engineering, part of the Chinese Academy of Sciences. He was part of a team who made multiple voyages in a specialized submersible, capable of withstanding the enormous pressures found at the bottom of the deep ocean floor.
During their dives, the team found a lot of fossils.

**Peng Xiaotong** (1:32)
In every dive, we found not just one, but maybe two, three or ten.

**Shamini Bundell** (1:38)
Analysis revealed that these fossils were whale bones, one of which was dated to 5.3 million years ago. The team had stumbled upon what they describe as a whale necropolis, and they got a paper about it out in Nature this week.
Now, when we think of fossils, we typically think of bones that need to be dug up. In this case, though, the fossilized remains of these wells were essentially just lying uncovered on the seabed in what's known as the Diamantina Zone, a deep 1200-kilometer-long indentation on the ocean floor west of Australia. Its location out in the ocean helps explain why these bones were lying there waiting to be discovered. Here's paleontologist Stephen Godfrey of the Calvert Marine Museum in the US to explain.

**Stephen Godfrey** (2:31)
Since you're so far away from any continent, right, you're not having the influx of continentally-derived eroded sediments carried by rivers. So you don't have sands or silt that are like covering over it. So that's why it was so readily available to the people in this submersible vehicle to sort of pick up all these specimens and bring them to the surface.

**Shamini Bundell** (2:52)
Xiaotong and his colleagues explored 32 small patches of the enormous Diamantina Zone and they found 476 fossils. Most of the fossils were fragments of beaked whales, including a previously unknown extinct species from this group. These whales are reclusive animals who inhabit deep waters, and the males in particular have hard bony beaks, which are much more likely than the bones of other species to survive and fossilize. While other species and other bones have been broken down over the millennia, these hard beaks remain. Strontium isotope dating showed that the oldest of these specimens had died approximately 5.3 million years ago.
The most recent bones, however, weren't fossils at all. They were the bodies of whales that had died relatively recently, and these remains were feeding a whole host of deep sea creatures.

**Peng Xiaotong** (3:43)
So that is like a seafloor garden. So you can see a bright star as well as some clam, which can use the chemical energy to grow up.

**Shamini Bundell** (3:56)
There were other organisms living on and around the remains too, like pale feathery bone-eating worms. These are creatures that rely on whale carcasses for food down in the depths where no light can reach. When whales die, their bodies bloat up with gas and may float up to the surface and drift on ocean currents. If and when they eventually sink to the seafloor, this so-called whale fall can provide a feast for deep sea creatures. A single whale carcass can sustain a miniature localised ecosystem for decades.
But when it comes to the whale necropolis that Xiaotong found, there's an important question that remains unanswered.

**Peng Xiaotong** (4:33)
The question is why so many choose this place to rest on peace.

**Shamini Bundell** (4:39)
The team's submersible has visited the ocean's depths many times. But the vast plains of the deep are relatively barren compared to the density of bones in this narrow region. Whale graveyards can be found in different places around the world. In some places, collections of fossils are thought to be the result of mass strandings or groups of whales killed by toxic algal blooms. But no other whale graveyard has been found as large as this one, as deep below the surface, or with this unique mixture of new and ancient bones. Since the team think that whale carcasses have been collecting in this spot for millions of years, it's understandable that Xiaotong wants to know why here?
The team's current best guess is that the shape of the seafloor trench essentially acts as a V-shaped funnel directing the flow of water.