 The tyrannosaurids spent as much as half its life in the juvenile phase before ballooning up to near @-@ maximum size in only a few years . This , along with the complete lack of predators intermediate in size between huge adult tyrannosaurids and other small theropods , suggests these niches may have been filled by juvenile tyrannosaurids . This is seen in modern Komodo dragons , where hatchlings start off as tree @-@ dwelling insectivores and slowly mature into massive apex predators capable of taking down large vertebrates . For example , Albertosaurus have been found in aggregations that some have suggested to represent mixed @-@ age packs . 
