Approximately 9 to 10 million years ago, a large group of carnivores died including saber-toothed cats and hyenas and ancestors of the red panda in a Spanish cave located in Madrid, referred to as the "Batallones-1". Researchers now conclude in a new study that the animals may have purposely gone into the cave and were trapped.

Other theories for the unusually massive amount of carnivores in the cave were previously offered. It was thought that either mass mortality or accidental falls into the cave were possibly factors of the large amount of dead animals. Another explanation was that perhaps the animals were washed up into the cave after dying at another location.

Fossils found in the cave indicated that 98 percent of the animals were carnivores and many of them were healthy adults, the theories offered could not explain those findings. The new study examined geological conditions that formed the cave, the age of the animals in the cave and the likely time frame that the animals entered into the cave.

Trampling marks and fractured bones were scarce, which led the researchers to believe that the animals did not die from the fall. It was concluded that the animals deliberately entered the cave in search of food or water and were unable to make their way out.

"Most probably, carnivores got trapped and remained alive for some time. Also, it is possible that carnivores were searching for water during drought periods and not necessarily for food. Further research is needed in order to ascertain the causes of death of carnivorans inside the cavity but exhaustion, hypothermia or poisoning from drinking water or toxic gases are options to consider," wrote the authors in the study published May 1 in the online journal PLOS ONE. The study was led by Soledad Domingo from the University of Michigan and colleagues from other institutions.