the spine of the Triceratops, providing a place to grip on. Furthermore, Krauss and Robinson suggest that this strategy would have been effective against other large ceratopsians and because the attack was done through an ambush, Tyrannosaurus would not have needed to compete in speed. Gregory S. Paul also discussed the defenses that hadrosaurs may have employed against tyrannosaurids such as Tyrannosaurus. Paul stated that duck-billed dinosaurs may have been able to kick out with its heavy footed hindlimbs. When faced with a predator, some duckbills were large and may have been able to use their size for protection, otherwise that the only apparent option for them to escape was to flee at maximum speed while attempting to land kicks on its pursuer. He would write that hadrosaurs, while using its forelimbs for locomotion, may have been able out turn tyrannosaurids. Paul wrote that hadrosaurs may have been gregarious (lived in groups) and may have prioritized trying to lose itself in the herd. He would also note that hadrosaurs were also lower-slung than their predators and may have therefore been able to use their forelimbs to push themselves through heavy vegetation; making it difficult for their predators to deliver effective bites. A study by Lisa Cooper, Andrew H. Lee, Mark L. Taper and John R. Horner suggested that hadrosaurs may have also protected themselves through their rapid growth rates, growing faster than their predators, thus giving them a size advantage and enabling them to breed early. In National Geographic News, Andrew Lee explained that hadrosaurs and Tyrannosaurus may have started out the same size when they hatched, but by 5 years of age hadrosaurs would be the size of a cow while Tyrannosaurus would still be the size of a dog. It would also be stated that the sample hadrosaur in the study, Hypacrosaurus reached a length 30 feet in 10–12 years. Tyrannosaurus on the other hand reached a length of 40 feet, but it took more than twice as long to reach that size. Tyrannosaurus may have had more endurance than hadrosaurs such as Edmontosaurus; though biomechanical studies have shown Edmontosaurus was the faster animal, its greater speed was only useful over short distances, while Tyrannosaurus, being better equipped for pursuit, likely would be able to, if able to keep the animal in sight, outpace and eventually subdue the hadrosaur once the herbivore tired. Such a strategy would save