Why 18,000 Animal Corpses Wound Up In A Cave In Spain

The remains of tens of thousands of ancient animals, including saber-toothed cats, hyena and an extinct bear-dog species in an underground cave in Spain have puzzled researchers since the cave's discovery in 1991. As if that weren't odd enough, 98 percent of the animal remains in the cave belong to large mammal carnivores.

There has long been speculation as to why and how the creatures wound up dead in a cave, but a new study refutes the old ideas and suggest a new theory of how the creatures wound up in the cavern millions of years ago.

The cave is more like a hole in the ground, and many of the smarter animals knew to avoid falling in. But M. Soledad Domingo her team believe the carnivorous animals, drawn to the smell of a meal in the form of dead or dying prey, willingly ventured down into the cave to look for food, not knowing that they would never be able to get back out.

"Only the carnivores were daring enough to enter," said study co-author Domingo, a paleontologist at the University of Michigan, according to LiveScience. "But they were unable to make their way out.

"We think that the carnivores were getting trapped, and then they became additional food for another coming carnivore."

Previous theories suggested that the animals were forced into the cave due to a natural disaster or that the remains were washed in from another location, Discovery News reports.

But Domingo thinks the abundance of carnivores, along with geological conditions under which the cave was formed, the age of individuals in the cave, the time frame over which they likely entered this pit and the lack of fractured bones or trampling marks negates the earlier theories.

To date, nearly 18,000 fossils have been recovered from the Cerro de los Batallones caves about 19 miles (30 km) outside of Madrid. The researchers say the cave likely had a visible opening in the ground, and that some herbivores, like the ancestors of modern elephants, giraffes and rhinoceros, occasionally fell in. But most herbivores were clever enough to avoid the fall.

A full report of the analysis is published in the journal PLOS ONE.