What Is the Purpose of the Temporalis Muscle in Cats?

Cats are obligate carnivores. They are designed to consume and to process protein-based diets, and their protein must come from meat. The structure of their jaw demonstrates their dietary requirement, in that it has only vertical movement; lateral movement is entirely absent from a cat̵7;s jaw. This structure prevents the cat from grinding grains and vegetable matter. However, cats̵7; jaws are highly adapted to grasp and to rip the flesh they must consume to survive.

  1. Evolution

    • The original sabertoothed cat, from which the familiar Smilodon sabertoothed ̶0;tiger̶1; evolved, had powerful jaws similar to the modern cat. However, their hunting style included the need for the ability to shear the throat of their prey. This shearing ability came at the expense of bite strength, which caused them to specialize in terms of the prey they were able to hunt. This structure makes the later sabertoothed cats anatomically unlike today̵7;s modern cats, which rely on powerful bites to bring down their prey. The modern cat's head shape is indicative of its ability to bite more powerfully in proportion to its size than previous feline species. It is also this head shape that has led to the evolution of a cat's powerful temporalis muscle.

    Anatomy of the Skull

    • Although the tiger can open its jaws wider than a house cat, it has a comparatively weaker bite for its size.

      The temporalis muscle is one of two of the ̶0;great muscles̶1; on the cat's head. It controls bite strength by raising the lower jaw to close the mouth. It anchors the small cats, which range in size from the average house cat to the cheetah and have skulls that are more rounded than those of the large cats, such as the lion. This difference in skull shape means that the temporalis muscle is shorter in those cats with rounded skulls. Interestingly, as the skull of the cat becomes larger and more elongated, the size of the brain pan becomes smaller. This difference in brain pan size, and therefore brain size, may be related to the need to anchor the larger temporalis muscle needed to maintain a killing bite.

    Biting

    • The strength of the cat̵7;s bite is in direct opposition to the distance to which it can open its mouth. That is, the shorter temporalis muscle in the cats with rounded heads has greater power to close the cats̵7; jaws than the longer muscle attached to cats with longer, narrower heads and muzzles. Prehistoric sabertoothed cats needed to open their mouths wider than modern cats to stab their prey with their elongated canine teeth. The modern clouded leopard is an evolutionary curiosity, being very similar to sabertoothed cats. This similarity in anatomy suggests that the clouded leopard is actually taking the evolutionary path toward being sabertoothed.

    Eating

    • The cat̵7;s temporalis muscle provides the animal with a great degree of jaw rigidity. The tradeoff for having a strong temporalis muscle is the inability to move the jaw from side to side. This rigidity limits the cat to tearing and swallowing its food. While no grinding or chewing is possible, neither are they necessary. Food that is torn and swallowed during eating is digested by the powerful stomach acids.