The Carnivore

As indicated on the "About" page, the dog as a species is a carnivore, known as "Canis Familiaris" or more recently as "Canis lupus". Dr. Robert K. Wayne, canid evolutionary biologist and geneticist at UC-Davis came to the following conclusion regarding the genetic relationship between wolves and dogs: "Dogs are gray wolves, despite their diversity in size and proportion."

Unlike other animals, carnivores have a layer of dense connective tissue/collagen fibers, called the stratum compactum, between the lamina propria (one of the innermost layers of the stomach lining) and the muscular layer of the stomach that functions to prevent perforations from ingested bones.

70% of bone is (inorganic) minerals of which 80% is calcium phosphate, 13% calcium carbonate, 2% magnesium phosphate, with the remaining 5% consisting of trace minerals. The remaining 30% of bone is the organic fraction, 90% of which is collagen with the rest consisting of chondroitin sulfate, keratin sulfate, and phospholipids.

Carnivores have a wide mouth opening in relation to their head size. This confers obvious advantages in developing the forces used in seizing, killing, and dismembering prey. Facial musculature is reduced since these muscles would hinder a wide gape, and play no part in the animals preparation of food for swallowing. In all mammalian carnivores, the jaw joint is a simple hinge joint lying in the same plane as the teeth. This type of joint is extremely stable and acts as the pivot point for the "lever arms" formed by the upper and lower jaws. The primary muscle used for operating the jaw in carnivores is the temporalis muscle. This muscle is so massive in carnivores that it accounts for most of the bulk of the sides of the head. The angle of the mandible (lower jaw) in carnivores is small. This is because the muscles (masseter and pterygoids) that attach there are of minor importance in these animals. The lower jaw of carnivores cannot move forward, and has very limited side-to-side motion. When the jaw of a carnivore closes, the blade-shaped cheek molars slide past each other to give a slicing motion that is very effective for shearing meat off bone. The teeth of a carnivore are discretely spaced so as not to trap stringy debris. The incisors are short, pointed and prong-like and are used for grasping and shredding. The canines are greatly elongated and dagger-like for stabbing, tearing and killing prey. The molars (carnassials) are flattened and triangular with jagged edges such that they function like serrated-edged blades. Because of the hinged-type joint, when a carnivore closes its jaw, the cheek teeth come together in a back-to-front fashion giving a smooth cutting motion like the blades on a pair of shears. The saliva of carnivorous animals does not contain digestive enzymes.

Striking differences between carnivores and herbivores are seen in these organs. Carnivores have a capacious simple (single-chambered) stomach. The stomach volume of a carnivore represents 60-70% of the total capacity of the digestive system. Because meat is relatively easily digested, their small intestines (where absorption of food molecules takes place) are short - about three to five or six times the body length. Carnivores are able to keep their gastric PH down around 1-2 even with food present. This is necessary to facilitate protein breakdown and to kill the abundant dangerous bacteria often found in decaying flesh foods.

The large intestine (colon) of carnivores is simple and very short, as its only purposes are to absorb salt and water. It is approximately the same diameter as the small intestine and, consequently, has a limited capacity to function as a reservoir. The colon is short and non-pouched. The muscle is distributed throughout the wall, giving the colon a smooth cylindrical appearance. Although a bacterial population is present in the colon of carnivores.