A biomechanical approach is used to model the mandibles of extant carnivoran predators (felids, canids, and hyaenids) as beams to gain insight into feeding behaviours. Because bite force applied at any given point along the mandible should be proportional to external dimensions at an analogous location (interdental gaps) on the mandible, patterns of variation in these dimensions will reflect the adaptation of the jaw to specific loads. The mandibular force profiles of extant carnivorans closely reflect particular feeding behaviours. Solitary hunters relying on a powerful canine bite to subdue their prey have a strong mandibular symphysis, while pack hunters delivering shallow bites have a relatively weaker one. Symphyseal shape also gives insight into the feeding behaviour of a predator: (1) a deeper-than-long symphysis indicates that stresses induced by the canine bite (or while cracking bones with the anterior dentition) are more important than those induced by struggling prey; (2) an equidimensional symphysis indicates that the symphyseal region is optimally designed to resist torsional stresses induced during prey capture and/or bone cracking; (3) a longer-than-deep symphysis indicates that stresses related to prey capture are predominant over those induced by the canine bite or while cracking bone. Mandibular force profiles of juvenile carnivorans also reflect documented ontogenetic changes in feeding behaviour. Because variation in mandibular cross-sectional properties are interpretable in terms of documented behaviours among extant predators, mandibular force profiles are developed to gain insight into the feeding behaviour of two extinct predators, Panthera atrox and Canis dirus. Results indicate that the feeding behaviour of P. atrox differed slightly from that of modern lions, as the powerful paws restrained prey more efficiently, while C. dirus hunted in a similar fashion to the gray wolf, although it may not have been an efficient bone cracker. Both extinct predators are inferred to have had a more powerful bite than their extant relatives.