Global cooling and lack of food led to loss of ancient cave bear

With at least a quarter of the world's mammal species, including big cats, rhinos and other large mammals, at risk of extinction from hunting and global warming, new research published from the Natural History Museum reveals that in the past global cooling was responsible for the demise of large mammals. One example is the now extinct European cave bear (Ursus spelaeus). The bear was, unlike its modern fish-eating counterparts, entirely vegetarian and could have starved to death as it ran out of food.

Its extinction was probably the result of climate cooling and habitat loss, almost 30,000 years ago, during the last ice age.

Professor Anthony Stuart, a Natural History Museum palaeontologist, said 'The disappearance of the cave bear around 27,500 years ago was probably due to the significant decline in quantity and quality of plant food, which in turn was the result of marked climatic cooling. Another mammal that went extinct in Europe at the same time was the spotted hyena (Crocuta crocuta). Other large mammals, or megafauna, such as woolly mammoth (Mammuthus primigenius), giant deer (Megaloceros giganteus) and cave lion (Panthera spelaea) disappeared much later, towards the end of the last ice age. They may have died out in the later Holocene warm period.'

Proposed causes for the extinction of ice age megafauna in Eurasia, North America and elsewhere include: environmental change, disease and over-hunting by humans. There is little evidence to suggest that the Neanderthal or their relatives the modern humans played a significant role in the decline of the bears. Earlier ideas involving the dependence of man on cave bears for hunting and the ritual worship of their remains have received no support from recent research either. Disease also seems unlikely. But the timing of their extinction does correlate with major changes in the environment.

Working with a colleague from the University of Vienna, Professor Stuart used new radiocarbon dating of cave bear fossil remains, from sites across Europe, to accurately establish the timing of their extinction. Their geographical distribution from Spain to the Urals, but not further east, suggests they were intolerant of continental temperature extremes.

The chemical analysis of cave bear bone collagen and study of their teeth indicate they were largely vegetarian, in contrast to the omnivorous diet of the modern brown bear. When they flourished, before the climate cooled, suitable high-quality vegetation must have been abundant as the bears grew to as heavy as 1,000 kg. Professor Stuart concludes that the reduction or disappearance of this rich vegetation due to global cooling is the most likely cause of cave bear extinction.

Several large charismatic species disappeared at different times within the late glacial period, such as the cave lion and woolly rhinoceros. Yet others, previously thought to have become extinct at the end of the late Pleistocene, such as the woolly mammoth and the giant deer, underwent dramatic shifts in distribution and survived well into the later Holocene period.

Professor Stuart concludes, 'Climatic cooling and subsequent decreased vegetation were probably responsible for the disappearance of cave bears from the Alpine region. However, we will continue to investigate the possibility that the species may have survived significantly later elsewhere, for example in southern or eastern Europe.'

The paper is published in the latest issue of the journal Boreas.