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The Tiny Culprit Behind A Graveyard of Ancient Whales

As the Pan-American Highway snakes its way through Chile, it passes through a place called Cerro Ballena. The site is in the middle of the driest desert in the world, and just an hour away from the mine where 33 unfortunate miners were trapped a few years back. That particular stretch of road is vital for ferrying the mining equipment and extracted minerals that are fuelling Chile’s economic surge. For that reason, a construction company was tasked with expanding the highway from two lanes to four.

But at Cerro Ballena, they unearthed something odd: the skeleton of a whale.

And then another. And another.

Dozens of them; different species; adults and juveniles. The construction crews had unearthed an entire whale graveyard.

“I wouldn’t wish a whale skeleton on anyone,” says Nick Pyenson, an expert on prehistoric marine mammals from the Smithsonian Institution. “You’re going to have to dig a lot.”

The dig site at Cerro Ballena. Credit: Nick Pyenson
The dig site at Cerro Ballena. Credit: Nick Pyenson

Pyenson first saw the graveyard in 2011 at the urging of his Chilean colleague Mario Suarez. He was amazed. Chile is famously rich in marine fossils anyway. The local tectonic plates push what was once ancient seafloor to more accessible heights and since the area is so dry, there is little vegetation and lots of erosion. But even in this place, which offers up its treasures with unusual abandon, the graveyard was something else.

But Pyenson was also troubled. The construction crews were treating the fossils with great care, jacketing the bones in plaster and transporting them to museums. But through their good work, they were also divorcing the bones from their surroundings. Without knowing where they were buried or the properties of the surrounding Earth, it would be impossible for scientists date them. And they’d never be able to answer the obvious and burning question: why had all these animals died in this same place?

Context was everything, and context was rapidly vanishing. The crews would finish their work by the end of 2011, and Pyenson knew that time was running out. “I remember literally looking at skeleton after skeleton and thinking, ‘Okay, what are we going to do? This is not what I signed up for.’”

Enter Adam Metallo and Vince Rossi. Pyenson calls them the laser cowboys. They are part of the Smithsonian’s 3-D digitisation team, and they flew over to Cerro Ballena with a smorgasbord of lasers and other scanning equipment. They worked continuously for several days, creating virtual models of the entire site and all its fossils, at extraordinarily high resolution. The bones have now all been removed, but their resting place lives on in a digital guise.

The laser jockeys at work. Credit: Nick Pyenson.
The laser jockeys at work. Credit: Nick Pyenson.

So far, the team have documented 40 separate skeletons, which are all between 6 and 9 million years old. Thirty-one of these were probably from the same species of rorqual whale—the family of giants that includes blues, fins and humpbacks.

There were other animals too, including a penguin, an extinct type of sperm whale, and two seals (one of which is new to science). There was a walrus-whale—a bizarre prehistoric dolphin with a tusked walrus-esque face.  There was even an aquatic sloth.

All of these specimens were found in an area of roadcut just 240 metres long and 20 metres wide. Pyenson estimates that there are hundreds of skeletons still buried in nearby areas that the construction teams didn’t touch. “What did they obliterate when they built the first two lanes of highway?” he wonders. “They must have dug up bone after bone.”

Most of the rorqual skeletons were complete, well-preserved, and belly-up. There was even a group of two adults and a youngster, log-jammed together and beautifully preserved. All of this suggests that they died at sea and were washed onto tidal flats, where they were quickly buried. And since the fossils were found in four separate layers, these mass strandings happened repeatedly in this same place.

La Familia--two adult whales and a calf. Credit: Nick Pyenson
La Familia–two adult whales and a calf. Credit: Nick Pyenson


What killed such a diverse group of animals, time and again? “Every explanation must work across all the taxa, and must also satisfy what you see about the bones and their arrangement,” says Pyenson. “And it has to explain the pattern four times.”

It probably wasn’t a virus, of the kind that’s killing off dolphins in the US. Such epidemics are usually species-specific, and unlikely to kill many different species including both mammals and birds. It wasn’t a tsunami either. A large wave wouldn’t have selectively killed larger animals and, besides, the surrounding rocks show that the area was mostly calm and stable.

Pyenson says there is only one cause that fits all the available evidence: these animals were poisoned by algae.

Algae thrive when coastal waters receive an unusual influx of nutrients, and some species release deadly toxins into the water. These ‘harmful algal blooms’ or ‘red tides’ are potent enough to kill whales and dolphins, which choke to death on the toxins.

At the end of 1987, fourteen humpback whales were stranded along the coastline near Cape Cod, USA, over a span of five weeks. Like the Cerro Ballena fossils, the strandees included males, females and calves. When scientists cut them open, they found plenty of Atlantic mackerel in their stomachs. And the mackerel, in turn, were loaded with algal toxins.

All the signs at Cerro Ballena suggest that those animals died in the same way. They showed no signs of injuries or bite marks. They ate a wide variety of diets but they were all at the top of their food webs, and such animals are more prone to algal poisoning.

There are also orange blotches on the bones, which Pyenson thinks are the remains of algal mats. On some specimens, he even found thousands of tiny spheres, which are exactly the right size to be dinoflagellates—the creatures behind harmful algal blooms. “It’s the closest we get to a smoking gun,” says Pyenson.

His theory is that iron minerals from the Andes in the east periodically washed into the ocean. This fertiliser was concentrated in the surface waters by upwelling currents, transforming the local algae into toxic blooms. Their poisons killed off local animals, which floated towards the coast and were stranded on the tidal flats.

This clearly happened many times in the past. Today, small whales and dolphins are often stranded en masse, but aside from the Cape Cod humpbacks, the large rorquals generally aren’t. Pyenson thinks that’s because so many of them have already died at the harpoons of whalers. Whale graveyards like Cerro Ballena may be a thing of the deep past, because we have turned the entire ocean into a whale graveyard.

Reference: Pyenson, Gutstein, Parham, Le Roux, Chavarria, Little, Metallo, Rossi, Valenzuela-Toro, Velez-Juarbe, Santelli, Rogers, Cozzuol & Suarez. 2014. Repeated mass strandings of Miocene marine mammals from Atacama Region of Chile point to sudden death at sea. Proc Roy Soc B. http://dx.doi.org/10.1098/rspb.2013.3316

14 thoughts on “The Tiny Culprit Behind A Graveyard of Ancient Whales

  1. “The researchers are not in a position to say for sure that harmful algal blooms were responsible for the mass strandings. There were no distinct algal cell fragments in the sediments; such a presence could have amounted to a “smoking gun”. What the team did find, however, were multiple grains encrusted in iron oxides that could hint at past algal activity.

    “There are tiny spheres about 20 microns across – that’s exactly the right size to be dinoflagellate cysts,” said Dr Pyenson.

    “They’re found in algal-like mats all around the site. We can’t say whether those were the killer algae, but they do not falsify the argument for harmful algal blooms being the cause in the way that the sedimentology falsifies tsunami being a potential cause.”

  2. It makes sense I suppose, but I wonder if there is a way of at least partially verifying the iron deposition for time frame and region. In other words can they pin down a time and place for an iron wash out into the ocean and verify if the iron would fertilize (optimal levels for algae) or poison (too much even for algae) the local populations.

  3. This is amazing!!! I want to go to whale hill! Were there no laws like we have in the USA for permitting a roadway or development to avoid wetlands, endangered species habitat or archeological significant places? 5 days is so short! Great job by the scientists in a mere 5 days!

  4. So when was this place named Cerro Ballena (Hill of Whales) — when they first started laying out the Pan-American Highway or was it just common knowledge that there are whale bones lying around even before?

  5. Great! Any chance someone could throw in a map so I have some context as to exactly where these fossils were found in relation to–for instance–the Andes?

  6. This is Chile. We allow the freaking Dakar rally to run over archeological sites, so don’t be surprised to find a highway at Cerro Ballena. Exploiting minerals and natural resources are more important for our presidents.

  7. “Whale graveyards like Cerro Ballena may be a thing of the deep past, because we have turned the entire ocean into a whale graveyard.”

    and that breaks my heart.

  8. Yes, we are killing the ocean,witness deep well horizon, and soon will be killing the land, witness Bristol Bay. Kiss your samon good bye.

  9. Just as an aside, this discovery was taken completely out of context and willfully misinterpreted by the Creation Today show with Eric Hovind, where previously in the same episode he criticized atheists for taking things in the bible out of context. This can be found in the April 3, 2014 episode entitled “Why Creation Matters – season three episode 24”. The relevant portion of the video is just about exactly 14 minutes in. He even mispronounces Dr. Pyenson’s name as Payeson in order, I suspect, to put his listeners off the trail in their efforts to Google this. I urge anyone who reads this to view the episode and write a letter or email to Eric Hovind and the creation today show. They can be reached at their website, creationtoday.org, by clicking the “about us” and then the “contact us” headings and then choose the “science questions” topic. I would love to see some people educated in this field reply to this video episode and set them straight on the proper interpretation of the facts

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