<P> Thomas Holtz Jr. would note that high depth perception of Tyrannosaurus may have been due to the prey it had to hunt; noting that it had to hunt horned dinosaurs such as Triceratops, armored dinosaurs such as Ankylosaurus and the duck - billed dinosaurs may have had complex social behaviors . He would suggest that this made precision more crucial for Tyrannosaurus enabling it to, "get in, get that blow in and take it down ." In contrast, Acrocanthosaurus had limited depth perception because they hunted large sauropods, which were relatively rare during the time of Tyrannosaurus . </P> <P> Tyrannosaurus had very large olfactory bulbs and olfactory nerves relative to their brain size, the organs responsible for a heightened sense of smell . This suggests that the sense of smell was highly developed, and implies that tyrannosaurs could detect carcasses by scent alone across great distances . The sense of smell in tyrannosaurs may have been comparable to modern vultures, which use scent to track carcasses for scavenging . Research on the olfactory bulbs has shown that Tyrannosaurus rex had the most highly developed sense of smell of 21 sampled non-avian dinosaur species . </P> <P> Somewhat unusually among theropods, T. rex had a very long cochlea . The length of the cochlea is often related to hearing acuity, or at least the importance of hearing in behavior, implying that hearing was a particularly important sense to tyrannosaurs . Specifically, data suggests that Tyrannosaurus rex heard best in the low - frequency range, and that low - frequency sounds were an important part of tyrannosaur behavior . </P> <P> A study by Grant R. Hurlburt, Ryan C. Ridgely and Lawrence Witmer obtained estimates for Encephalization Quotients (EQs), based on reptiles and birds, as well as estimates for the ratio of cerebrum to brain mass . The study concluded that Tyrannosaurus had the relatively largest brain of all adult non-avian dinosaurs with the exception of certain small maniraptoriforms (Bambiraptor, Troodon and Ornithomimus). The study found that Tyrannosaurus's relative brain size was still within the range of modern reptiles, being at most 2 standard deviations above the mean of non-avian reptile EQs . The estimates for the ratio of cerebrum mass to brain mass would range from 47.5 to 49.53 percent . According to the study, this is more than the lowest estimates for extant birds (44.6 percent), but still close to the typical ratios of the smallest sexually mature alligators which range from 45.9--47.9 percent . </P>

When did the tyrannosaurus rule as an apex predator