massive thighs and robustly built legs suited for moderate fast-running. In addition, the prominent pelvis of Achillobator has its own specialized femoral muscle retractors that may indicate a strong ability for leaping. In 2016, Scott Persons IV and Currie examined the limb proportion of numerous theropods and found that compsognathids, troodontids and tyrannosauroids were cursorial animals with many taxa recovered with relatively high CLP (cursorial-limb-proportion) scores. Dromaeosaurids however, were recovered with low CLP scores, with Achillobator scoring −5.3 suggesting that it was not adapted to maintain high speeds for extended amounts of time. Predatory behavior In 2009 Longrich and Currie suggested that while other dromaeosaurids filled a variety of specialized ecological niches like the slender unenlagiines, eudromaeosaurs, such as Achillobator, retained a conservative life-style and filled the niche of large-bodied predators of often medium to large-sized prey. Manning and team in 2009 tested the function of the sickle claw of dromaeosaurids by analyzing the biomechanics of how stresses and strains would be distributed along the claws and into the limbs, and using comparisons within the curvature of the dromaeosaurid sickle claw on the foot with curvature in modern birds and mammals. They found that they were ideal for climbing and for a ground-dwelling life style. Peter Mackovicky stated that the analysis might be correct on primitive dromaeosaurids (such as Microraptor) being tree-climbers, however, this does not explain why giant animals like Achillobator or Utahraptor retained sickle claws as they were likely far too large to have climbed trees with any great faculty. Mackovicky suggested that larger dromaeosaurids adapted the claw to be used exclusively for a more aggressive predatory behavior. The striking resemblance between the feet and legs of dromaeosaurids and those of accipitrid birds of prey, led Fowler et al. 2011 to propose that dromaeosaurids hunted in a similar way to those of raptorial birds. They found that the feet and legs of dromaeosaurs resemble those of eagles and hawks by having an enlarged second claw and a similar range of flexion, but the metatarsals share more resemblance to those of owls. The model RPR (Raptor Prey Restraint), proposes that dromaeosaurs leaped into their prey, immobilizing it with their body weight, and then hold it tightly with the large, sickle-shaped claws; afterwards, the dromaeosaur would start to feed on the animal while it's still alive and the death will eventually come from blood loss and organ failure. The arms