Based on the abundance of hadrosaur remains in late Cretaceous sediments, scientists believe that they must have been among the most successful of all dinosaur groups, yet these bipedal herbivores had no obvious means of defense. They did not have horns, plates, spikes or armoured skin. Their top speed was described as a slow waddle and the best defense they could provide was possibly kicking and stamping with their hind legs. Their young in particular would have been exceedingly vulnerable to predation. So how did these creatures become one of the most successful group of dinosaurs in the Cretaceous?