Cave fossil offers new clues about the huge hyenas that once roamed Europe

Nestled in the mountain slopes of northern Spain is a cave called Los Aprendices, which has been collecting bones and sediment for hundreds of thousands of years. A few years ago, scientists discovered the ancient skeleton of one of Europe's most famous Ice Age carnivores deep within this cavern: Crocuta spelaea, the cave hyena.

Remains of these extinct creatures can be found within hundreds of caves all across Europe, but most of these fossils are just bits and pieces – complete or even partial skeletons are extremely rare. But the skeleton discovered in Los Aprendices is an exception. More than 100 bones represent over half of the animal's whole body, making this the most complete cave hyena ever discovered on the Iberian Peninsula, and one of the most complete in all of Europe. Recently, these prized remains were examined by a group of Spanish researchers, offering up fresh clues about this ancient carnivore.

A panoramic photo of the cave hyena skeleton from Los Aprendices cave. Image: Saurqué et al. 2017

The fossils came from a single adult, around six to ten years of age, who seems to have died alone in the cave around 143,000 years ago. Today's hyenas are mostly restricted to Africa, but in the past, several species called Europe home as well, including the cave hyena – a close relative, and possibly a subspecies, of the modern-day spotted hyena.

Cave hyena bones were first found in Los Aprendices cave back in 2005, but it wasn't until 2012 that this new skeleton's hiding place was discovered. "To reach the gallery where the fossil remains were found," the scientists note, "we have to pass through a narrow aisle (some 50 cm in height) that leads to another gallery at a lower level." This lower area was once open to the outside, but the entrance was filled in with sediment long ago.

But why do the hyenas have such a shoddy fossil record? Their feeding preferences may be to blame, the researchers explain. "The lack of more complete skeletons of this species in the fossil record may be a consequence of their scavenger dietary habits, including cannibalism."

Close-up of the cave hyena's skull, bulkier than that of its living hyena relatives. Image: Saurqué et al. 2017

Beefier than their spotted cousins, cave hyenas had stockier limbs and larger bodies, and weighed in at an average of 88 kilograms (194 lbs), which is more like the size of a modern-day jaguar. And this new skeleton was a particularly impressive specimen. "[T]he estimated body mass is 103kg (227lbs), which makes it one of the largest cave hyenas ever recorded," the researchers note.

Those proportions would have made the cave hyena less of a runner, but a more powerful hunter than its relatives. "C. spelaea could use its weight and strength to reduce larger prey," the palaeontologists explain. "Consequently, this huge carnivore was capable of accumulating bones of large prey like horses, woolly rhinos, giant deer and woolly mammoth."

Many Ice Age creatures have "cave" slapped in front of their names, since so many fossils are found in such subterranean spots. But unlike the cave lion, for example, cave hyenas actually did spend a lot of their time in cavernous hangouts, where they would gather the bones of the creatures they preyed upon. Their dens are among the best sources of fossil collections from the late Ice Age.

A drawing of a cave hyena near Los Aprendices cave, shown feeding on the carcass of a Spanish Ibex, inspired by the fossils found nearby the new cave hyena skeleton. Image: Saurqué et al. 2017

So far, the Los Aprendices hyena is the only one of its species found in this particular cave, but other animals also left bones behind, including a few small mammals like rodents and rabbits, as well as at least one snake and two Spanish ibex, an adult and a newborn.

And there was something else in the cave as well – another carnivore. This mysterious second predator, however, didn't leave any fossils behind. Many of the hyena's bones show breaks and punctures left by sharp teeth, but this isn't the work of other hyenas. "If the hyena had been with a clan of cave hyenas at the time of its death," the researchers say, "these other hyenas would have scavenged on its carcass, causing a large part of the skeleton to disappear and dispersing the bones." Instead, the marks look like the handiwork of a smaller scavenger, likely a wolf or European leopard.

Cave hyenas appear in the European fossil record around 300,000 years ago, but this new skeleton is one of the oldest known from the Iberian Peninsula. This makes it an important piece of hyena evolutionary history, allowing paleontologists to understand what these big predators were like before they disappeared at the end of the Pleistocene with so many other large, fascinating Ice Age creatures.

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Top header image: Arno Meintjes/Flickr