Cave bear

Lore & Background

Cave bear skeletons were first described in 1774 by Johann Friedrich Esper in his book Newly Discovered Zoolites of Unknown Four Footed Animals. While scientists at the time considered the skeletons could belong to apes, canids, felids, or even dragons or unicorns, Esper postulated they actually belonged to polar bears. Twenty years later, Johann Christian Rosenmüller, an anatomist at Leipzig University, gave the species its binomial name. The bones were so numerous that most researchers had little regard for them. During World War I, with the scarcity of phosphate dung, earth from caves where cave bear bones occurred was used as a source of phosphates; when the 'dragon caves' in Austria’s Styria region were exploited, only the skulls and leg bones were kept.

Many caves in Central Europe have skeletons of cave bears inside, such as the Heinrichshöhle in Hemer and the Dechenhöhle in Iserlohn, Germany. A complete skeleton, five complete skulls, and 18 other bones were found inside Kletno Bear Cave in 1966 in Poland. In Romania, in a cave called Bears' Cave, 140 cave bear skeletons were discovered in 1983. Remains assigned to 'cave bears' sensu lato from the Late Pleistocene exhibit a strong degree of morphological and size variability, and have often been assigned to their own species, including Ursus rossicus, Ursus ingressus, Ursus kanivetz, Ursus kudarensis, Ursus eremus, and Ursus spelaeus sensu stricto. These populations show considerable genetic divergence, though whether these species should be regarded as synonyms of U. spelaeus is debated.

Both the cave bear and the brown bear are thought to be descended from the Early Pleistocene species Ursus etruscus. The date of divergence between the ancestors of cave bears and brown bears has been estimated at around 1.2–1.5 million years ago. The earliest remains of the cave bear lineage are assigned to Ursus deningeri, which first appears at the end of the Early Pleistocene, around 1.2–0.8 million years ago. The transition between Ursus deningeri and Ursus spelaeus is often given as the Last Interglacial (130–115,000 years ago), although the boundary is arbitrary, and intermediate taxa have been proposed. In 2005, scientists recovered and sequenced the nuclear DNA of a cave bear that lived between 42,000 and 44,000 years ago, confirming that the cave bear was more closely related to the brown bear and polar bear than to the American black bear, but had split from the brown bear lineage before the distinct eastern and western brown bear lineages diversified, and before the split of brown bears and polar bears. A recent study showed that both species had some hybridization between them.

Reader's Guide

The cave bear is significant as a well-known Pleistocene megafauna species whose abundant remains in caves across Europe and Asia have provided extensive insights into its biology, evolution, and extinction. Its common name reflects its close association with caves, where it hibernated more frequently than brown bears. The species exhibits considerable morphological and genetic variability, leading to ongoing debate among experts about whether Late Pleistocene cave bears represent a single species or a complex of up to six distinct species. This uncertainty highlights the challenges in interpreting fossil diversity. The cave bear's largely herbivorous diet, inferred from tooth morphology and stable isotope analysis, contrasts with the omnivory of modern brown bears, and its dental adaptations—such as the loss of premolars and molarization—illustrate evolutionary responses to a vegetarian diet. The recovery of nuclear DNA from a 42,000- to 44,000-year-old specimen demonstrates the potential for ancient DNA studies to clarify evolutionary relationships, showing that cave bears are more closely related to brown and polar bears than to American black bears, and that some hybridization occurred between cave bears and brown bears. The species' extinction around 24,000 years ago during the Last Glacial Maximum marks the end of a lineage that had persisted for over a million years.

Did You Know?

• Cave bear skeletons were first described in 1774 by Johann Friedrich Esper, who initially thought they belonged to polar bears.
• During World War I, earth from caves containing cave bear bones was used as a source of phosphates due to the scarcity of phosphate dung.
• In Romania's Bears' Cave, 140 cave bear skeletons were discovered in 1983.
• The cave bear's three anterior premolars gradually reduced and then disappeared, possibly in response to a largely vegetarian diet.