Beavers and marmots in a Neanderthal cave palimpsest: small-prey consumption at Valdegoba Cave (Burgos, Spain)

For decades, the story of Neanderthal survival has been told through the lens of the hunt for large animals. We picture them tracking herds of deer or bison across the open plains, relying on these massive prey to provide the bulk of their calories. This focus on big game has created a blind spot in our understanding of their diet, leaving a gap between the well-documented large animals and the tiny creatures like rabbits, birds, and tortoises that we know they also ate. The question remains: did they ever fill the middle ground? Did they regularly hunt or process animals that were too small to be a primary target but too large to be a mere snack? Understanding this helps us see Neanderthals not just as big-game hunters, but as flexible foragers who could adapt their diet to whatever the landscape offered, a skill that would have been crucial for surviving the harsh, shifting climates of the Ice Age.

In a cave high in the mountains of northern Spain, researchers have found evidence that Neanderthals did indeed look to the middle ground. At Valdegoba Cave, a team of scientists uncovered a mixed collection of bones belonging to two very different large rodents: the Eurasian beaver and the alpine marmot. These are not the tiny mice or voles often found in ancient sites, nor are they the massive ungulates that dominate the archaeological record. Instead, they represent a size class that had been largely overlooked. The study reveals that while these animals were not the main course for the Neanderthals living there, they were part of the menu. The researchers found direct proof that humans had processed these animals, cutting into their flesh and skin, adding a new layer of complexity to our picture of how these ancient people lived.

The cave itself, located near the town of Huérmeces in Burgos, sits in a narrow canyon carved by a river. It holds layers of dirt and stone that date back to a time roughly 140,000 to 120,000 years ago, a period when the climate was shifting between cold and slightly warmer phases. For years, archaeologists have known that Neanderthals lived here, leaving behind stone tools and the bones of chamois, rabbits, and birds. But when the team began to sort through the animal remains, they found something unusual: a significant number of beaver and marmot bones. The collection was surprisingly rich, containing 171 identifiable pieces of beaver and 60 pieces of marmot. This was not a single event where one animal died; it was a palimpsest, a complex layering of history where different forces had brought these animals into the cave over time.

The challenge for the researchers was to figure out who brought these animals there. Caves are natural traps. Beavers live near water and do not hibernate, so finding their bones in a cave usually means a predator dragged them in, or a flood washed them there. Marmots, on the other hand, live in burrows and hibernate for months. They often die in their underground homes, and their bodies can end up in caves through natural collapse or by being carried in by other animals. The team had to untangle whether these bones were there because of natural death, because of predators like wolves or hyenas, or because Neanderthals had brought them in to eat.

The answer lay in the details of the bones themselves. The researchers examined every surface for signs of how the animals died and what happened to them after. They found that the beaver bones showed signs of being chewed by carnivores, with tooth marks and pits that matched the bite of foxes and larger predators. Some bones even showed signs of having been digested, suggesting they had passed through the stomach of a predator. The marmot bones, however, were mostly skulls and teeth, with very few body parts, a pattern that often happens when animals die naturally in a burrow and are only partially recovered. But amidst this mix of natural and carnivore activity, the team found the smoking gun: cut marks.

On a few specific bones, the researchers saw clear lines carved into the bone by a sharp stone tool. These marks were found on a beaver leg bone, a hip bone, and a jaw, as well as on a marmot jaw. When they looked at these marks under a powerful microscope, they saw tiny scratches and specific shapes that can only be made by a human knife, not by a tooth or a rock. These marks were located in places where a person would skin an animal or cut the meat off the bone. This provided direct, undeniable evidence that Neanderthals had processed both the beaver and the marmot. It was the first time such clear evidence of Neanderthal processing of these two specific animals had been found together at the same site.

The study also looked at the ages of the animals to see if the Neanderthals were hunting them selectively. For the beavers, the bones belonged to a mix of young and adult animals, with a concentration of those around two years old. This is the age when young beavers leave their family groups to find their own territory, a time when they might be more vulnerable to hunters. For the marmots, the bones belonged mostly to older adults and very young ones, a pattern that looks more like natural death over time rather than a targeted hunt. This suggests that while Neanderthals were taking advantage of these animals, they were not specializing in them. They were not running a beaver farm or a marmot hunt; they were opportunistic. They took what was available, perhaps when a beaver was caught near the river or a marmot was found in a burrow, adding a valuable source of meat and fur to their diet without making it their primary focus.

The presence of these animals also tells a story about the landscape around the cave at that time. Beavers need permanent rivers and lush vegetation along the banks, while marmots need open, rocky slopes and grasslands. Finding both of them in the same cave indicates that the Neanderthals were living in a diverse environment that offered both wet, wooded areas and dry, open hills. This variety of habitats would have supported a wide range of food sources, allowing the Neanderthals to be flexible in their choices.

Ultimately, this research fills a missing piece in the puzzle of Neanderthal life. It shows that their diet was not limited to the largest animals or the smallest snacks. They were capable of exploiting medium-sized prey, using stone tools to process beavers and marmots just as they did with deer and rabbits. The evidence from Valdegoba Cave suggests that these ancient people were skilled at reading their environment and using every resource they could find. They did not rely on a single strategy for survival; instead, they adapted to the complex and changing world around them, turning even the large rodents of the Ice Age into a part of their daily sustenance.