 Noted hadrosaur expert Jack Horner is currently the major advocate of the idea that Tyrannosaurus was exclusively a scavenger and did not engage in active hunting at all . Horner has presented several arguments to support the pure scavenger hypothesis . The presence of large olfactory bulbs and olfactory nerves suggests a highly developed sense of smell for sniffing out carcasses over great distances . The teeth could crush bone , and therefore could extract as much food ( bone marrow ) as possible from carcass remnants , usually the least nutritious parts . At least some of its potential prey could move quickly , while evidence suggests that it walked instead of ran . 
