Ancient Giants: What Happened to Portugal's Enormous Brown Bears?

A recent study of Pleistocene bear remains from Portugal finds no trace of cave bears, but brown bears large enough to be mistaken for them.

There are a number of animals I love, and often when I ask others what their favorite animals are, they give me extraordinarily weird and wonderful creatures. For me, my answers always felt ‘boring’ somehow, but I maintain my favorite animals constantly vying for first place are wolves and bears.

Today’s story isn’t about wolves, though, but about bears. Brown bears (Ursus arctos) once roamed basically all of Europe, though their reign would not last, and they became locally extinct in many of the same places they once called home. One place I had never really considered bear territory is Portugal.

Bears are ecological powerhouses; without them, the environment changes. Understanding their role in past environments and how they went extinct can help us help those bears still hanging on today. 

With that in mind, researchers led by Dr Darío Estraviz-López and colleagues examined more than 500 bear bones from ancient Portuguese cave sites. What they found may surprise you, for one, every single specimen was a brown bear, no cave bears (Ursus spelaeus). And second, they were giants compared to their modern counterparts.

Why did Portugal seemingly have no cave bears, and why were the brown bears so massive? What led to their eventual shrinkage and regional extinction? Let’s find out.

Meet the Brown Bears

Brown bears belong to the bear family, which today has eight living species, but once also included the massive, now-extinct cave bear, a cousin of the brown bear that split off roughly 1.5 million years ago.

Brown bears originated in Asia around 620,000 years ago. From here, DNA evidence suggests they moved towards Western Europe and arrived there around half a million years ago.

There, they became one of the most common European carnivores alongside cave bears, though crucially, when cave bears died out in the last ice age, brown bears survived.

They appeared in Iberia (a peninsula which encompasses Spain, Portugal, Andorra, Gibraltar, and a small sliver of southern France) around 250–200,000 years ago. Here, they became more common in the Late Pleistocene but were still far outnumbered by cave bear fossils, and interestingly, the two species rarely overlap.

That said, the cave bear’s family tree does reach into Portugal, just not the cave bear itself. 

“Since a few years ago we know that the ancestor of cave bears, the Deninger’s bear (Ursus deningeri) lived during the Middle Pleistocene in Portugal, but fossils of the famous Late Pleistocene cave bear (Ursus spelaeus) remain elusive,” Estraviz-López explained.

To date, 16 Portuguese sites have yielded brown bear fossils, though the evidence is patchy. The site with the most brown bear bones is Furninha, where roughly 700 brown bear bones have been recovered. That is more than any other site in Iberia bar one, the Sima de Illobi in Spain. Alongside this, Portugal has the only known open-air bear tracks in the fossil record, preserved in wind-blown sand dunes at Praia do Cavalo around 30,000 years ago, plus over a hundred claw marks along the walls of Algar do Vale da Pena.

But the brown bears’ presence in Portugal would not last; after the Ice Age, evidence of their presence began to thin. A few bones from Copper Age settlements and a shoulder blade from Roman times speak to their continued existence, as do some medieval documents suggesting brown bears were still widespread at least until the 16th century. The last brown bear vanished from Portugal by the late 1800s.

Studying Bear Bones

To better understand Portugal’s brown bear history, bear bones from six different sites were studied. Among them were bones from Furninha (~100–70,000 years), one of Portugal’s best-studied Pleistocene caves, but also a poorly documented one.

When going through older collections, it is rather common to come across bones with numbers scribbled on them. These numbers usually correspond to catalogued information (site, layer, species, type of bone, age, size, etc.). 

Now, imagine instead of labelling individual bones, you threw them all in a box, labelled the entire thing number 780 and called it a day. That’s what happened in some cases at Furninha.

Other sites were better catalogued, like Oliveira, while others still are completely missing. By that, I mean the location is unknown; we know the name of the cave, but not where it is. We have barely a dozen bones from it, and no reliable date at all.

From these locations, the authors analysed 535 bones.

Big Bad Brown Bear

The results were fascinating; not a single bone belonged to a cave bear. Some had lived with painful deformities, while others were so large they could almost be mistaken for cave bears.

Furninha had the largest assemblage of bear bones, from young to old, healthy and sick. The mix of bones suggested this was once a hibernation den, where bears over generations came and died in their sleep. Their bones were not just large but thick, making them look a bit like cave bears. Other sites showed similar trends; in fact, one bear from a much later site was estimated to weigh around 387 kg.

With time, however, their bones decreased in size. Early Holocene bears in NW Spain averaged 261 kg for males and 140 kg for females.

To put that into perspective, modern Iberian bears weigh between 144 and 103 kg. That’s a ~40% shrinkage in males and 25% in females over the last several thousand years.

But why did brown bears suddenly get so much smaller? And where were the cave bears?

Well, size reduction in European Pleistocene mammals is actually a well-known phenomenon, but the drivers differ.

The authors have an interesting hypothesis. Remember how there are no cave bears in Portugal? Well, this may be due to the tendency of cave bears to basically reuse the same caves (and therefore habitats) for generations. By contrast, the brown bear is a bit more adventurous and will migrate to new habitats and caves more readily. This may explain why cave bears seemingly did not exist in Portugal; they simply never got that far.

The authors propose that these massive brown bears filled the ecological niche that these cave bears would have occupied. However, over time, with human hunters actively selecting the biggest, most prized bears, their size steadily reduced.

For a modern parallel, the authors point to African elephants, where ivory poaching has driven the spread of tusklessness, thus showing how evolution selects against the very trait humans target.

But this was no ‘sudden’ event rather played out over millennia. 

“The reduction in the size of modern Iberian bears probably occurred gradually over several thousand years. It may have begun when Ice Age humans increasingly occupied caves and continued with the first farmers, who cleared forests for fields and pastures. Under Roman rule, urban expansion, agriculture, mining and the growing demand for timber and fuel further transformed and fragmented bear habitats. Bears were also captured for use in Roman arena spectacles,” said co-author Dr Ana García-Vázquez.

So bears were being squeezed out of their dens, then out of their forests, then out of the landscape entirely. 

“Large bears were also prestigious hunting targets. During the Middle Ages, bear hunting was largely restricted to the nobility, although bears were less highly prized than deer. The most dramatic decline came with the widespread use of firearms, as brown bear populations progressively disappeared from southern to northern Iberia. In eighteenth-century Asturias, in northern Spain, around 150 bears were reportedly killed each year. By the 1950s, the Cantabrian population had fallen to only about 40 individuals; today, it is almost ten times larger.”

So, Portugal never had cave bears because they are creatures of habit, which simply seems to have never made the journey there. In their absence, brown bears grew larger to fill that ecological niche. But when the pressure that made great size worthwhile faded, and hunters started picking off the largest bears, the giants shrank to their modern sizes until they vanished from Portugal completely.

Maybe wolves and bears are a “boring” answer, but there’s nothing boring about a 300 kg bear sleeping through a Portuguese winter 80,000 years ago. Knowing what we lost, and how, is the only way to hold on to what’s left.

What’s your favorite animal out of interest and why? And what other reasons could there be that cave bears seemingly never reached Portugal (besides, we haven’t found them yet)?

Let me know your thoughts, and if you’d like to support the countless hours I pour into researching, writing, and bringing these hidden corners of history to life, why not Buy Me A Coffee

Reference

Estraviz-López, D., García-Vázquez, A., Ríos, M., & Grandal-d’Anglade, A. (2026). Pleistocene brown bears from Portugal: Morphometric trends, paleoenvironmental drivers and paleobiological inferences. Palaeogeography, Palaeoclimatology, Palaeoecology, 113964. https://doi.org/10.1016/j.palaeo.2026.113964