Drinking with dinosaurs

Did dinosaurs prefer Perrier, Evian or plain river water? They might not have had the expensive advertising campaigns to help them choose, but dinosaurs were loyal customers, and single minded about which kind of water they drank.

French scientists have been peeling back the layers of dinosaur eggshells to uncover the secrets of dinosaur drinking habits. The chemistry inside an eggshell can reveal many facts about what the animal ate and drank in the weeks prior to laying the egg.

For example, the eggs laid by chickens that quaff Perrier have subtle differences to eggs laid by chickens that put up with tap water. In the same way, dinosaurs that slurped from the swamp laid eggs that were distinct from those laid by dinosaurs that sipped from a sparkling spring.

Each type of mineral water has its own distinctive blend of minerals. By measuring the variations in levels of minerals (such as magnesium, strontium and iron), it is possible to fingerprint where the water came from and whether it was rainwater, spring water, river water or swamp water. The distinctive signature survives through an animal's digestive system and can remain intact for millions of years in a fossilised egg.

So when a dinosaur glugged a few gallons of water, the chemistry of that water was imprinted into the eggshell and left a signature that can still be seen today. Parisian scientists Isabelle Cojan, Maurice Renard and Laurent Emmanuel have looked at the chemistry of dinosaur eggs from two areas in Aix en Provence, France. One area used to be a floodplain, while the other was a forest.

The scientists wanted to see if the dinosaurs tended to settle down in one place or were nomads. "Eggs form over a short period of time so they provide us with an instant picture of animal conditions," explains Cojan. Since water has such a distinct chemical signature, it was an ideal way to trace the dinosaur's footsteps. Sure enough, the fossil eggs from the ancient floodplain showed a different chemistry from those from the forest. Floodplain dinosaurs slurped from local rivers, while forest dinosaurs drank water rich in minerals that had circulated through the rocks, picking up volcanic salts on the way.

"The distinctive differences indicate that the dinosaurs settled for some time at the places where they laid their eggs, and that migration was limited," says Cojan.

Although the floodplain was close to the forest, the eggshells show that each group of dinosaurs stuck to its own territory and its associated drinking water. Cojan and her team are now extending the study to other areas of France and eventually hope to look at global drinking habits. Of course, eggshells can't tell us the whole story.

They only reveal dinosaur lifestyles for the weeks prior to laying an egg. Perhaps dinosaurs were more outgoing and sociable when they weren't worrying about where to lay eggs. What is more, the eggshells can only tell us about what the female dinosaurs chose to drink. None the less, we do know that French, female, nesting dinosaurs were passionate about their water.