London: For the first time, scientists claim to have found evidence which proves that just like birds dinosaurs were also migrating when conditions becoming hard for them to live at a particular region.

The first persuasive evidence that dinosaurs were also migrating comes from a study of teeth of Camarasaurus, one of the most common species of sauropod.

It grew to 15 metres long and lived in Wyoming and Utah in the late Jurassic period. Its fossils have been found on what was once a low-lying floodplain, which would have periodically dried out, an agency reported.

Researchers, led by Henry Fricke from the University of Colorado, looked at the oxygen isotopes in 32 fossil teeth and found the ratio of isotopes in teeth -- which is determined by the water the dinosaurs drank --  was different to that in carbonate rock from the floodplain that carries the signature of the water it formed in.

This suggests that Camarasaurus sometimes left the area, the researchers said in a report published in journal Nature.

One tooth revealed that the oxygen isotopes gradually changed over five months, strengthening the idea that the migration was seasonal.

The most likely interpretation is that the dinosaurs moved to greener pastures at higher altitudes when conditions became hard, said Fricke.

When the dinosaurs migrated, predators such as allosaurs probably followed them, he added.

Palaeontologists have long suspected that some dinosaurs migrated, but this is the first solid evidence of it, said Paul Barrett of the Natural History Museum in London.

Camarasaurus must have put a lot of pressure on food resources, so it makes sense that they moved around. Barrett suspected rarer sauropods such as Haplocanthosaurus didn't need to migrate.