Highway Expansion Uncovers Whale Graveyard

Paleontologists have pieced together clues to solve the mystery behind the largest collection of whale fossils ever found.

A trove of over 40 whale and other marine animal fossils was discovered in Chile during an expansion of the Pan-American Highway. The group of skeletons pictured above is called “La Familia,” although scientists can’t be sure if the two adults and calf entombed together are actually related. The picture was built from more than 300 individual images (the blurry edges have to do with the limited coverage and overlap at the edges of the assemblage of skeletons from separate photos). Credit: Nicholas D. Pyenson/Smithsonian Institution
A trove of over 40 whale and other marine animal fossils was discovered in Chile during an expansion of the Pan-American Highway. The group of skeletons pictured above is called “La Familia,” although scientists can’t be sure if the two adults and calf entombed together are actually related. The picture was built from more than 300 individual images (the blurry edges have to do with the limited coverage and overlap at the edges of the assemblage of skeletons from separate photos). Credit: Nicholas D. Pyenson/Smithsonian Institution

icon of wave with words "oceans month" next to itThis story has been resurfaced as a part of Oceans Month, where we explore the science throughout the world’s oceans and meet the people who study them. Want to dive in with us? Find all of our stories here.


Four years ago, while doing roadwork on the Pan-American Highway, a Chilean construction crew got a surprise when it stumbled upon a massive collection of whale bones. An international group of paleontologists has since unearthed an unprecedented number of whale skeletons from four distinct layers at the site, dating back six to nine million years.

“I never thought I’d have to work with 40 [whale skeletons] at once,” says Nick Pyenson, curator of Fossil Marine Mammals at the Smithsonian’s National Museum of Natural History, who led the excavation. “It was overwhelming.”

The majority of the fossils represented large, filter-feeding baleen whales. But the site—known as Cerro Ballena (Spanish for “whale hill”)—also contained the remains of nine other kinds of marine vertebrates, including seals, sperm whales, dolphins, and one species previously only recovered in Peru: a walrus whale that Pyenson describes as having a “bizarre Admiral Ackbar-looking face.” The findings are described in a recent edition of The Proceedings of the Royal Society B.

Chilean and Smithsonian paleontologists study several fossil whale skeletons at Cerro Ballena, next to the Pan-American Highway in Atacama Region, Chile, in 2011. Credit: Adam Metallo/Smithsonian Institution
Chilean and Smithsonian paleontologists study several fossil whale skeletons at Cerro Ballena, next to the Pan-American Highway in Atacama Region, Chile, in 2011. Credit: Adam Metallo/Smithsonian Institution

Once Pyenson and his team got over the enormity of their task, they began to wonder why the ancient animals had been buried in droves in essentially the same spot repeatedly over time.

[Listen to a daily audio diary of the narwhal.]

Hints came from studying tiny details in fossil scans taken by the “laser cowboys”—two members of the Smithsonian’s 3D digitization lab—whom Pyenson brought in for a week to image the fossils in order to retain information, such as how they were arranged, that would inevitably be lost as the skeletons were removed and shipped off to Chilean museums.

Pyenson’s team learned that most of the whales were preserved with their bellies facing up, suggesting they had died at sea rather than on land. “If they wash up alive, their blowholes definitely will be pointing up [instead], because they definitely need to breathe air,” says Pyenson.

All skeletons were also remarkably free of bitemarks made by scavengers, indicating that the creatures didn’t stay long in the ocean after dying—rather, they probably washed up on land soon after perishing.

[Track Earth’s history in a column of coral.]

Wondering how the creatures at Cerro Ballena could have died, Pyenson recalls a similar mass death that occurred in the late 1980s, when 14 humpback whales mysteriously washed up on the shores of Cape Cod. “The humpbacks showed no signs of trauma,” he says. “In some cases they were seen on a whale watch 90 minutes before they washed up dead.” Subsequent testing found that the whales died from asphyxiation after feasting on Atlantic mackerel loaded with saxitoxin, a neurotoxin found in dinoflagellates. The microorganisms had exploded in population off the Cape Cod coast in what’s called a harmful algal bloom.

Could such a phenomenon explain the ancient Chilean deaths, too? Algal blooms are known to recur off the western coast of South America, fueled by the iron-rich runoff from the Andes Mountains in combination with ocean upwellings that bring nutrients to the surface. Pyenson speculates that such a bloom occurred millions of years ago, creating a toxin that poisoned all of the marine animals found at the Chilean site. Strong currents soon pushed the carcasses onto the Cerro Ballena tidal flat, where they were stranded once the water receded. Thousands of years later, a similar scenario occurred, taking down more animals. The process repeated two more times, laying the groundwork for the site as we know it today.

Given the staggering number of whale fossils recovered, Pyenson says that Cerro Ballena should be recognized as a UNESCO World Heritage site, calling it Chile’s version of the United States’ Dinosaur National Monument. But as unique as the area seems, the algal bloom hypothesis suggests that there are other sites like it. Indeed, areas off the western coasts of California and Namibia, where upwellings are common, have probably experienced similar conditions that have created whale graveyards, as yet undiscovered.


Get science images that will blow your mind with our newsletter, Picture of the Week.

Meet the Writer

About Jessica McDonald

Jessica McDonald is a health reporter for WHYY, Philadelphia’s public radio station. She is also a former Science Friday web intern.

Explore More