Being second-in-command, Bruton is shown to be very rude and cranky to any newcomers, and usually follows Kron's orders. Bruton shows no mercy at first and refuses to listen to any of Aladar's suggestions. However, Bruton later reforms when he wards off two Carnotaurs that had followed Aladar into the cave, the lemurs, Baylene, Url and Eema into a cave. Bruton sacrifices his own life to save them, which proves that he truly has a heart after all.
It is entirely possible that Bruton and Kron are two different subspecies of Iguanodons. They both possess very different physical traits compared to other Iguanodons, such as being larger, looking much more different and having different skin colour patterns. Not only is Bruton only slightly taller than Aladar, but he is also shown in several shots to be nearly three times the size of Aladar in width and mass.
In the movie, as Aladar and his lemur family are running to escape a pack of Velociraptors, they run into the herd of dinosaurs and the leader Kron pushes Aladar out of the way telling him to stay out of his way to which Bruton yells at Aladar, "You heard Kron! Move it!" When the herd stops to find a resting spot for the night Bruton tells Kron that there's a much safer spot further down, but Kron tells Bruton that the herd will sleep where they are for the night and tells Bruton to tell the herd that they have found their resting spot for the night to which Bruton does. When Kron, Bruton, and Kron's sister Neera pass Aladar, Aladar asks Kron if he can talk to him, to which Bruton snaps at Aladar to, "Get lost, kid!" but Kron tells Bruton to relax and listens to what Aladar has to say, but when Aladar asks him to slow down for the slower dinosaurs Kron refuses and tells him to let him do the thinking.
The next day, Bruton tells all the dinosaurs to get up because Kron has said that everyone goes. Aladar's lemur friend Zini makes a remark about Bruton saying, "The charm never stops around here." Hearing this, Bruton then turns to Aladar and asks, "You say something?" to which Aladar replies, "No, sir."
Bruton then tells Aladar that he and Zini (who he calls a "little parasite") better get moving unless they have a death wish. Zini then calls Bruton ugly under his breath. Kron tells Bruton to give the herd the orders about getting to the water on the other side to which Bruton tells the herd to keep up because if a predator catches them they're on their own and then he orders the herd to move out. On the way, Kron tells Bruton that the herd is moving too slow and Bruton says that he'll pick up the pace and orders the herd to move faster. When they reach the lake Kron and Bruton discover that the lake is a dryed with no water and Kron orders Bruton to take a scout and check the entire perimeter to see if there's any water. Bruton and the scout find no water on their search to which the scout replies, "I think we should get back." But Bruton tells him to keep it down. Then Bruton spots a shadow of a Carnotaur and tells the Scout that they should leave but before they can, a Carnotaur appears from behind and grabs the scout by the tail, killing him. Then another Carnotaur appears and tries to kill Bruton but he manages to escape with wounds. Bruton rushes back to Kron and tells him about the Carnotaurs and Kron coldly blames Bruton for leading the Carnotaurs to them, saying that maybe Bruton could feed the Carnotaurs with his hide. He then orders Bruton to move the herd out to which Bruton does.
On the way Bruton is left behind to die because of his wounds but he is found by Aladar, Baylene, Url, Eema and the lemurs. Aladar offers to help Bruton but Bruton tells him that he just just needs some rest and orders Aladar to get away from him. Aladar tells Bruton that if he changes his mind that they'll be in those caves nearby. Bruton later decides to join the dinosaurs and lemurs inside the cave and Plio nurses Bruton's wounds from a plant that grew on Lemur Island. Bruton then asks why Aladar pushes the herd on with false hope, to which Plio replies it's hope that has gotten them this far. Bruton then asks why doesn't he let the herd accept their fate and that he has just accepted his own, which is to die in the caves; to him, it's simply the way things are. Plio tells Bruton that the plant will help him and that it's his choice, not his fate, to die if he gives up.
That night, the two Carnotaurs appear at the cave, to which Bruton tells Aladar that they should wake the others and move deeper into the cave. However, as the dinosaurs and lemurs are moving, the Carnotaurs spot Aladar and grab him, but Bruton (remembering about what happened to the scout earlier) pushes into the battle and shouts at Aladar to help the others while he holds off the Carnotaurs. Bruton manages to fight off the Carnotaurs. After knocking one of the beasts into a supporting stalactite, he notices that rocks from the cave are beginning to crumble, which gives him an idea. He charges and rams the second Carnotaur onto another stalactite, causing the part of the roof to collapse on them. Aladar comes back and tries to help Bruton, but the rocks fall on Bruton before he can. After the rocks are done falling, Aladar digs through them and finds Bruton who has died from being crushed by the rocks. Aladar mourns the death of his friend to which Plio replies, "You did what you could." Though one of the Carnotaurs managed to survive the cave-in, Bruton's sacrifice was not completely in vain, as the other Carnotaur died with him, and the surviving Carnotaur would eventually be defeated during the film's climax.