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 when they were way too large to have climbed trees. Mackovicky suggested that larger dromaeosaurids adapted the claw to be used exclusively for a more aggressive predatory behavior.