Researchers solved the mystery of four mass whale stranding that took place between six and nine million years ago.
Researchers believe the standings, which all occurred in the same place, where a result of toxic algae, a Smithsonian news release reported. The large "whale skeleton graveyard" is located in the Atacama Desert of Northern Chile; the site is called Cerro Ballena, which means "whale hill" in Spanish.
The researchers found 40 large baleen whales at the site (which was discovered during the expansion of the Pan-American Highway), as well as a species of sperm whale and a "walrus-like whale." Altogether the researchers found 10 ancient species at the site.
The skeletons were found in four separate layers, suggesting multiple whales had been stranded there on several occasions; the skeletons' orientation also suggests the animals died at sea and washed ashore.
Toxic algal blooms such as red tide are believed to be related to the majority of modern mass strandings.
"There are a few compelling modern examples that provide excellent analogs for the patterns we observed at Cerro Ballena-in particular, one case from the late 1980s when more than a dozen humpback whales washed ashore near Cape Cod, with no signs of trauma, but sickened by mackerel loaded with toxins from red tides," Nicholas Pyenson, paleontologist at the Smithsonian's National Museum of Natural History and lead author of the research, said in the news release. "Harmful algal blooms in the modern world can strike a variety of marine mammals and large predatory fish. The key for us was its repetitive nature at Cerro Ballena: no other plausible explanation in the modern world would be recurring, except for toxic algae, which can recur if the conditions are right."
Harmful algal blooms are enhanced by erosion-based nutrients such as iron (which are fed into the ocean by rivers). The South American Andes are extremely iron-rich, making the region an excellent place for toxic algae to bloom.
"Cerro Ballena is the densest site for individual fossil whales and other extinct marine mammals in entire world, putting it on par with the La Brea Tar Pits or Dinosaur National Monument in the U.S.," Pyenson said. "The site preserves marine predators that are familiar to modern eyes, like large whales and seals. However, it also preserves extinct and bizarre marine mammals, including walrus-like whales and aquatic sloths. In this way, the site is an amazing and rare snapshot of ancient marine ecosystems along the coast of South America."
