The Hunting Methods of Theropod Dinosaurs

In 1881 the American fossil hunter Charles Marsh suggested that all meat-eating dinosaurs (the carnivores of the family group dinosauria) be lumped together; he deemed this grouping “theropods,” meaning “beast-feet.” The first theropods appeared around 225 million years ago, in the Triassic Period, the first period of the Mesozoic Era. They survived till about 65 million years ago, when the dinosaurs vanished—giving them a lifespan of 160 million years. Some scientists believe that birds are the descendents of the theropod dinosaurs; if this is true, then the lifespan of the theropods is, in actuality, around 230 million years. 

Most theropods were lightly-built with large heads; they had blade-like teeth with serrated edges; long, slender legs giving them speed greater than most dinosaurs; long, curved claws that tapered to tips, especially on the hands; and they had air pockets in their skulls and vertebrae, as well as an extra joint in the mandible that allowed them to eat large pieces of food. 

Theropods can be divided into two groups: the ceratosaurs and the tetanurans. The ceratosaurs are found in the late Triassic and early Jurassic periods, though some Cretaceous carnivores are placed in this group; the ceratosaurs are identified by four functional fingers on each hand and clawed toes on the foot. Some popular ceratosaurs are Dilophosaurus and Ceratosaurus. The tetanurans is the largest group of theropods, incorporating all theropods not found in ceratosauridae; they are identified by three-clawed fingers on the hands and three large toes on the feet, each foot having a smaller toe on the inside of the foot. Tetanurae further divides into two sub-groups, the carnosaurs and the coelurosaurs. The carnosaurs are a group containing most of the large tetanurans (i.e. Allosaurus and Sinoraptor), though, ironically, one of the largest—though not the largest—theropod (Tyrannosaurus) is placed with the coelurosaurs. The coelurosaurs contained most of the Cretaceous theropods, and included strange theropods such as the dromaeosaurs, the ornithomimosaurs, and the oviraptors. 

One of the finest tools for pondering theropod hunting techniques is our observations of the hunting methods of modern-day carnivores. In the world of terrestrial carnivores (a term referring to animals that derive more than 95% of their food in the form of vertebrate flesh), there are three major predatory tactics: ‘grapple-&-slash’, ‘grapple-&-bite’, and ‘pursuit-&-bite’. It's reasonable to assume that carnivorous dinosaurs employed these tactics against their prey (such as Apatosaurus, Triceratops, or Stegosaurus). 

Grapple-&-Slash is a hunting tactic used by modern-day cats. Predators using this method have highly-compressed, recurved, blade-like claws on their hands and feet; their hind limbs are powerful, and their tails are used as dynamic stabilizers allowing quick-turns in ambushing prey. These hunters do not chase their food; they ambush it. The animals lie in wait, then ambush the prey when it draws close; after a quick chase, they latch onto the animals with their forelimbs; the prey is then taken down with a combination of slashes from the forelimb, disemboweling kicks with the hind limbs, and/or suffocation with the mouth. These hunters usually aren’t very fast in long runs, but yet they're excellent sprinters—perfect for ambushing. When it comes to carnivorous dinosaurs, many paleontologists believe that dromaeosaurs (including such dinosaurs as Velociraptor and Deinonychus) employed this tactic (Jack Horner, a renowned paleontologist, advanced this idea). Contrary to what “Jurassic Park” will tell you, however, the dromaeosaurs probably didn't make the majority of their kills with the “killer claws” on their feet; these claws were probably used to latch onto the prey (like a mountaineer’s hook) while making the killing slashes with their forelimbs. Dromaeosaurs, in general, fit this type of hunting method: they have short and stout legs, their claws and the sickle-claws on their feet match the proportions of these modern hunters; and their tails probably acted as dynamic stabilizers. 

The Grapple-&-Bite  method of hunting is employed by modern raptorial birds, who swoop down on their prey and carry them into the air while killing the victims with their jaws or beaks. Predators using this method are characterized by claws that are curved but fairly round in the cross-section; the claws are at the end of powerful limbs. Like the “Grapple-&-Slash” hunters, these are ambushers. The hunting tactic is as follows: wait in ambush, then suddenly attack, seizing the prey with the forelimbs, and killing the prey with bites to the neck or back, then dragging the prey out-of-reach of other predators. The claws would be used for holding the prey while the jaws are the main killing tool, whereas in the Grapple-&-Slash tactic, the claws are the main dispatching weapon. Many paleontologists believe most large theropods—such as Allosaurus—utilized this tactic: their hand claws are proportionate to that of the raptorial birds, but they were not well-adapted for killing prey (thus they probably used these claws to hold the prey while the jaws did the gruesome work). 

Pursuit-&-Bite is a method utilized by modern-day dogs, wolves, hyenas, and cheetahs. These animals don't have highly-curved claws, and the claws are rounded in the cross-section; however, they have powerful jaws and necks, long teeth, and relatively long limbs. Using this method, an animal will run down its prey after a fairly long chase, seize the prey in their jaws, and then kill the prey with a combination of biting and suffocation. The claws, if used at all, are used to pin down the prey or keep it stable while the jaws do their thing. Many paleontologists believe Tyrannosaurus was a “pursuit-&-bite” hunter: he had proportionally long legs, and his claws weren't well-adapted for killing; also, its large head had long, serrated teeth. No doubt his bite pressure was enormous. 

“Were some theropods pack-hunters?” Lending credence to the idea that some carnivores were pack-hunters are the fossilized remains of several Coelophysis skeletons at Ghost Ranch in New Mexico, as well as several Allosaurus remains at the Cleveland-Lloyd Query in Utah. Many modern carnivores—such as lions, for example, and cheetahs—hunt in packs.

“Were some theropods scavengers?”  It should be noted that hunting and scavenging are not exclusive behaviors: many dinosaurs may have been (and probably were) hunters and scavengers (after all, who in their right mind would pass up a free meal?). The locale and environment of the predator could have played a role in whether or not it was a scavenger or a hunter: in Africa, the region in which a predator lives often determines whether it is a hunter or a scavenger. We can never underestimate how the environment plays a crucial role in animal behaviors.

Ultimately, any discussion on the hunting methods of theropod dinosaurs should be made in the context of humility. When we talk of the predatory methods of dinosaurs, we run into a bit of a problem: all we have are fossils. We cannot study these dinosaurs up-close. We cannot study their behaviors, their social organizations, or the way they interacted with their environment. In the end, we can take the best guesses we can and humbly acknowledge that we could be—and, to an extent, may very well be—wrong.