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Mardi, 22 Novembre 2011 16:20

Ancient Cave Lion Bones Reveal Big Cats' Diet

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Ancient Cave Lion Bones Reveal Big Cats' Diet

By Andrew Curry, ScienceNOW

A quarter larger than today’s lions, the European cave lion was one of the biggest cats around 12,000 years ago. Now, an unusually sophisticated analysis of its bones is revealing what these creatures ate—and why they may have disappeared.

Ancient Cave Lion Bones Reveal Big Cats' DietAlthough they were certainly massive cats, the term “cave lion” is a bit of a misnomer. Unlike today’s lions, males probably didn’t have manes, and they appear to have been solitary hunters. What’s more, though their bones are best preserved in caves, they probably lived in the open. But they did have one thing in common with their modern relatives: they appear to have worried humans. The big cats show up in ice age cave paintings and in ivory figurines, suggesting that they were a major concern for our ancestors.

To figure out what these lions hunted, biogeologist Hervé Bocherens and colleagues at the University of Tübingen in Germany, analyzed bone samples from 14 cave lions—found in four caves in France and central Europe—that lived between 12,000 and 40,000 years ago. The team focused on the chemical content of the bone collagen, which is often well-preserved, even in bones tens of thousands of years old. By incinerating a tiny fragment of preserved bone—usually less than a milligram—researchers can identify the molecules inside it and determine an animal’s diet.

Scientists have perfected the technique over the years. It was used recently to look at the diet of Neandertals, but this is one of the first studies to use it to look at a nonhuman predator—and the analysis is now sensitive enough to look several steps down the food chain. This enabled Bocherens to determine not only what cave lions ate but also what their prey ate. And that made it possible to tell, for example, whether lions were targeting full-size cave bears or their more vulnerable cubs, because adults and babies eat different diets themselves. “There’s a difference between the [chemical] signal of adults and babies,” Bocherens says. “Babies drink the milk of the mother.”

As it turned out, this distinction was important. Bocherens’s analysis, reported in the 6 December issue of Quaternary International, revealed that the cave lions occasionally ate bear cubs but not adults. Their favorite food, however, was reindeer, which Bocherens and his team determined consumed massive quantities of lichen, much as their modern descendants did. The cave lion diet, Bocherens says, appears to have been much more finicky than that of today’s lions, which eat just about anything they can catch.

The results may provide new insights into why cave lions died out. When Europe’s climate began to warm about 19,000 years ago, the landscape gradually changed from chilly, open steppes to denser forests. That would have made an inhospitable habitat for reindeer and for the cave lions that depended on them for food. (Cave bears were also dying out at the same time.)

Experts say the ability to dissect ancient diets so thoroughly is a tantalizing tool but that this particular study is too geographically limited to be conclusive about cave lions. “It’s quite astonishing that you can quite convincingly demonstrate what predators were eating tens of thousands of years ago,” says Anthony Stuart, a biologist at Durham University in the United Kingdom. “One obvious thing to do is extend the study to a wider area” to see how diets might have varied geographically. Cave lions, he notes, “ranged from Spain across Europe and Siberia all the way to the northwestern part of North America.”

Ralf-Dietrich Kahlke, a paleontologist at the Senckenberg Institute in Weimar, Germany, says the increasing precision of isotopic analysis may also provide a window into a larger question, namely, what kind of world our earliest ancestors inhabited. Knowing not only what extinct predators ate but also what the animals they ate consumed could help scientists build a sort of ancient food chain they don’t currently have. It could also tell us more about the plants and vegetation of the environment. “If we can detect the environmental conditions under which prey lived,” Kahlke says, “we can decide what conditions allowed humans to spread.”

This story provided by ScienceNOW, the daily online news service of the journal Science.

Image: Researcher Hervé Bocherens with a cave lion skull. Analysis of lion bones (inset) shows the extinct beasts’ preferred prey was reindeer. (Wolfgang Gerber/Universität Tübingen)

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