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Titanosaur dinosaurs 鈥� thought to have been the largest animals to walk on Earth and which have been found on every continent 鈥� might have gone hungry and thirsty when building nests and laying eggs.

at the University of Buenos Aires in Argentina and her colleagues studied stable carbon and oxygen isotopes in 71 titanosaur eggshells and a tooth, all unearthed from three fossilised nesting sites in Argentina. The fossils are between 66 million and聽100 million years old.

Food and water contain carbon and oxygen, but the mix of stable isotopes of each element varies depending on environmental conditions. Given that these isotopes transfer to the tissues of the animal that consumed them, it is possible to use the ratios of them within eggshells or teeth to get a glimpse into the environmental conditions under which these organic tissues formed.

The eggshells contained more of a particular oxygen isotope which is associated with higher evaporation rates of water than the tooth. This suggested that the eggs formed while the titanosaurs were living in relatively arid environments in which the dinosaurs ingested less water from drinking and eating.

The team compared the results with isotope data from titanosaur eggshell finds from similar mid-latitude regions in other parts of the world and found they all fitted a pattern of forming in drier conditions.

鈥淚t seems that most titanosaurs needed similar conditions for nesting,鈥� says Leuzinger.

It was already thought that titanosaurs lived in herds and ate plants, suggesting they probably had to migrate in order to get enough food to fuel their enormous bodies. If they lingered permanently in arid areas where they laid their eggs, they would quickly munch through the available vegetation.

The latest study indicates that titanosaurs, in mid-latitudes at least, possibly went to more arid areas only to reproduce and may have had to fast during nesting, akin to how certain present-day animals, such as emperor penguins, build up fat reserves to survive without eating and drinking during reproductive periods.

Titanosaurs also lived beyond the mid-latitudes, in the Antarctic, but whether the findings apply to them isn鈥檛 known. 鈥淲hether the titanosaurians discovered in Antarctica needed similar conditions for nesting remains an open question until titanosaur eggs are found there and analysed for their stable isotope composition,鈥� says Leuzinger.