Reinterpreting the Locomotor Ability of Tyrannosaurus Through Bird-Like Gaits

When Tyrannosaurus Ran Like a Bird: Rethinking the Locomotion of the Tyrant King

For decades, one of the most famous debates in paleontology has centered on whether Tyrannosaurus was an active apex predator or primarily a scavenger. At the heart of this debate lies a fundamental question: how well could Tyrannosaurus actually move? Could such a gigantic animal run fast enough to chase down prey, or was it too massive for effective pursuit?

Because Tyrannosaurus was enormous—adult individuals could weigh several tonnes—its bones and muscles would have experienced tremendous forces during locomotion. Excessive speed could potentially increase the risk of injury, fractures, or catastrophic falls. As a result, scientists have spent decades attempting to reconstruct the locomotor abilities of Tyrannosaurus through skeletal proportions, muscle reconstructions, biomechanical modelling, and computer simulations.

Body size comparison between Tyrannosaurus, humans, ostriches, and polar bears（Image source：Boeye, A. T et al. (2026).， CC BY 4.0 。）

To further investigate how Tyrannosaurus moved, a recent study compiled extensive anatomical data from numerous specimens, including hip height, hindlimb proportions, and gait data from modern birds, which were then incorporated into biomechanical models. Unlike many previous studies of dinosaur locomotion, this research specifically focused on foot-strike patterns—that is, which parts of the foot contacted the ground first during movement. Different foot-strike patterns can significantly influence stride frequency and maximum running speed.

The study suggests that many previous models may have underestimated the locomotor performance of Tyrannosaurus. Earlier reconstructions often assumed a “proximal-first” foot strike, in which the more proximal parts of the foot contacted the ground first. However, evidence from theropod trackways, tyrannosaur footprints, and the locomotion of modern birds indicates that a more realistic gait involved the distal portions of the foot—especially the toes—making contact first, similar to birds. This “distal-first strike” (DFS) pattern would likely increase stride frequency while also distributing stresses across the hindlimb more efficiently, resulting in improved running performance.

According to the study, the hindlimb anatomy of Tyrannosaurus already possessed many bird-like characteristics, suggesting that its locomotion may have resembled that of large terrestrial birds more closely than previously assumed. Under a bird-like gait model, both stride frequency and estimated top speed increase, implying that Tyrannosaurus may have been more agile than traditional depictions suggest.

Current estimates place the running speed of Tyrannosaurus at approximately 5–11 metres per second. Several factors likely constrained higher speeds, including whether the hindlimbs could withstand the enormous forces generated during rapid locomotion, whether the muscles could produce sufficient power, and the stresses exerted on the skeleton while running.

The study also found substantial differences in locomotor ability among Tyrannosaurus individuals of different ages and body sizes. The approximately 6.5-tonne specimen MOR 555 was estimated to move at around 9.5 m/s, whereas the much larger 9.5-tonne specimen FMNH PR 2081 was estimated at only 6.3 m/s. Meanwhile, the smaller 1.4-tonne specimen LACM 23845 may have reached speeds of up to 11.4 m/s. These differences suggest that Tyrannosaurus likely occupied different ecological niches throughout its life, with juveniles and adults potentially targeting different prey animals.

Estimated speeds of Tyrannosaurus specimens of different sizes and ages（Image source：Boeye, A. T et al. (2026).， CC BY 4.0 。）

Researchers also noted that juvenile Tyrannosaurus and the smaller tyrannosaurid Nanotyrannus may both have been relatively fast predators. How these animals partitioned ecological niches, and how Late Cretaceous ecosystems supported multiple large predators simultaneously, remains an important area for future study.

Modern birds differ substantially from humans in their running mechanics. Birds generally exhibit shorter ground contact times, higher stride frequencies, and smoother transitions between walking and running. Larger birds rely even more heavily on high stride frequencies while maintaining proportionally shorter strides. Interestingly, several of these locomotor traits also appear to have been present in Tyrannosaurus.

A running ostrich（Image source：Charles J. Sharp， CC BY-SA 4.0 。）

If Tyrannosaurus used a distal-first foot-strike pattern, its foot would have presented a larger contact area during each stride cycle. Combined with thicker cartilage and extensive ligamentous support, this may have reduced stress on the feet and metatarsals while increasing the ability to withstand ground reaction forces. Rather than relying purely on enormous strides, Tyrannosaurus may have moved more like a giant flightless bird, using relatively high stride frequencies to maintain speed. Such locomotion would also allow quicker shifts in body balance and hindlimb positioning, further reinforcing the idea of bird-like running mechanics.

Despite these similarities, important differences between Tyrannosaurus and modern birds remain. One of the most significant distinctions involves the tail and hip function. In living birds, the femur plays a relatively limited role during locomotion, while movement is driven more by distal limb elements such as the knee and lower leg. In contrast, the hip and femur remained central to locomotion in non-avian theropods such as Tyrannosaurus. This difference is closely tied to the presence of a massive, muscular tail, which played an important role in femoral retraction and energy storage.

Previous studies have also suggested that the ankle musculature of Tyrannosaurus may have been less developed than that of modern birds, indicating that its locomotion still differed from that of true avians. Future research may help reassess these limitations.

Overall, this study suggests that the locomotion of Tyrannosaurus may have been more bird-like than previously thought. Future biomechanical models that integrate muscles, joints, ligaments, and dynamic tail movement into more advanced three-dimensional simulations could provide a far more accurate reconstruction of how Tyrannosaurus moved and how fast it could run.

These studies are important not simply because they estimate how fast Tyrannosaurus could move, but because they help researchers better understand how this giant predator hunted. Only by accurately reconstructing its locomotion can we truly understand how Tyrannosaurus captured the large prey animals that fossil evidence confirms it hunted.

（Author: Bai Leng）

Reference：

Boeye, A. T., Atkins-Weltman, K. L., King, J. L., Swann, S. (2026). Evidence of bird-like foot function in Tyrannosaurus. Royal Society Open Science.