I've got an idea. Tell me what you think.
Bronson left them at the ruins of the elf city because he saw a large, reptillian tail dissapearing into the forest. Thinking it was an animal he could recruit, he followed it. It turned out to be a lone monster that ambushed him. He and his animals manage to come out of the fight with a draw. He flees after wounding the monster. He gets back to the ruins, but no one is there.
Some time later, he meets up with a huge pack of assorted raptors, which are living and working together due to being pushed out of their own territory by the monsters. He convinces them to go with him. Later, they are attacked by a pack of two dozen monsters. Bronson, the mountain lion, 1 heavily wounded quetzalcoatlus(the giant pterodactly), 8 dromeasaurus(raptors), and the robin are the only survivors. Bronson meets up with the group sometime after that.