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Predatory behavior

The brain of Smilodon had sulcal patterns similar to modern cats, which suggests an increased complexity of the regions that control the sense of hearing, sight, and coordination of the limbs. Felid saber-tooths in general had relatively small eyes that were not as forward-facing as those of modern cats, which have good binocular vision to help them move in trees. Smilodon was likely an ambush predator that concealed itself in dense vegetation, as its limb proportions were similar to modern forest-dwelling cats, and its short tail would not have helped it balance while running. Unlike its ancestor Megantereon, which was at least partially scansorial and therefore able to climb trees, Smilodon was probably completely terrestrial due to its greater weight and lack of climbing adaptations. Tracks from Argentina named Felipeda miramarensis in 2019 may have been produced by Smilodon. If correctly identified, the tracks indicate that the animal had fully retractible claws, plantigrade feet, lacked strong supination capabilities in its paws, notably robust forelimbs compared to the hindlimbs, and was probably an ambush predator.

The heel bone of Smilodon was fairly long, which suggests it was a good jumper. Its well-developed flexor and extensor muscles in its forearms probably enabled it to pull down, and securely hold down, large prey. Analysis of the cross-sections of S. fatalis humeri indicated that they were strengthened by cortical thickening to such an extent that they would have been able to sustain greater loading than those of extant big cats, or of the extinct American lion. The humerus cortical wall in S. fatalis was a 15 % thicker than excpected in modern big cats of similar size. The thickening of S. fatalis femurs was within the range of extant felids. Its canines were fragile and could not have bitten into bone; due to the risk of breaking, these cats had to subdue and restrain their prey with their powerful forelimbs before they could use their canine teeth, and likely used quick slashing or stabbing bites rather than the slow, suffocating bites typically used by modern cats. On rare occasions, as evidenced by fossils, Smilodon was willing to risk biting into bone with its canines. This may have been focused more towards competition such as other Smilodon or potential threats such as other carnivores than on prey.

Debate continues as to how Smilodon killed its prey. Traditionally, the most popular theory is that the cat delivered a deep stabbing bite or open-jawed stabbing thrust to the throat, killing the prey very quickly. Another hypothesis suggests that Smilodon targeted the belly of its prey. This is disputed, as the curvature of their prey's belly would likely have prevented the cat from getting a good bite or stab. In regard to how Smilodon delivered its bite, the "canine shear-bite" hypothesis has been favored, where flexion of the neck and rotation of the skull assisted in biting the prey, but this may be mechanically impossible. However, evidence from comparisons with Homotherium suggest that Smilodon was fully capable of and utilized the canine shear-bite as its primary means of killing prey, based on the fact that it had a thick skull and relatively little trabecular bone, while Homotherium had both more trabecular bone and a more lion-like clamping bite as its primary means of attacking prey. The discovery, made by Figueirido and Lautenschlager et al., published in 2018 suggests extremely different ecological adaptations in both machairodonts. The mandibular flanges may have helped resist bending forces when the mandible was pulled against the hide of a prey animal. It has been experimentally proven by means of a machine that recreates the teeth, and simulates the movements of jaws and neck of Smilodon fatalis (The "Robocat") on bison and elk carcasses, that the stabbing bite to the throat is a much more plausible and practical killing technique than the stabbing bite to the belly.

The protruding incisors were arranged in an arch, and were used to hold the prey still and stabilize it while the canine bite was delivered. The contact surface between the canine crown and the gum was enlarged, which helped stabilize the tooth and helped the cat sense when the tooth had penetrated to its maximum extent. Since saber-toothed cats generally had a relatively large infraorbital foramen (opening) in the skull, which housed nerves associated with the whiskers, it has been suggested the improved senses would have helped the cats' precision when biting outside their field of vision, and thereby prevent breakage of the canines. The blade-like carnassial teeth were used to cut skin to access the meat, and the reduced molars suggest that they were less adapted for crushing bones than modern cats. As the food of modern cats enters the mouth through the side while cutting with the carnassials, not the front incisors between the canines, the animals do not need to gape widely, so the canines of Smilodon would likewise not have been a hindrance when feeding. A study published in 2022 of how machairodonts fed revealed that wear patterns on the teeth of S. fatalis also suggest that it was capable of eating bone to a similar extent as lions. This and comparisons with bite marks left by the contemporary machairodont Xenosmilus suggest that Smilodon and its relatives could efficiently de-flesh a carcass of meat when feeding without being hindered by their long canines.

Despite being more powerfully built than other large cats, Smilodon had a weaker bite. Modern big cats have more pronounced zygomatic arches, while these were smaller in Smilodon, which restricted the thickness and therefore power of the temporalis muscles and thus reduced Smilodon ' s bite force. Analysis of its narrow jaws indicates that it could produce a bite only a third as strong as that of a lion (the bite force quotient measured for the lion is 112). There seems to be a general rule that the saber-toothed cats with the largest canines had proportionally weaker bites. Analyses of canine bending strength (the ability of the canine teeth to resist bending forces without breaking) and bite forces indicate that the saber-toothed cats' teeth were stronger relative to the bite force than those of modern big cats. In addition, Smilodon ' s gape could have reached over 110 degrees, while that of the modern lion reaches 65 degrees. This made the gape wide enough to allow Smilodon to grasp large prey despite the long canines. A 2018 study compared the killing behavior of Smilodon fatalis and Homotherium serum, and found that the former had a strong skull with little trabecular bone for a stabbing canine-shear bite, whereas the latter had more trabecular bone and used a clamp and hold style more similar to lions. The two would therefore have held distinct ecological niches.